[//000000001]: # (critcl\_howto\_use \- C Runtime In Tcl \(CriTcl\)) [//000000002]: # (Generated from file 'critcl\_howto\_use\.man' by tcllib/doctools with format 'markdown') [//000000003]: # (Copyright © Jean\-Claude Wippler) [//000000004]: # (Copyright © Steve Landers) [//000000005]: # (Copyright © 2011\-2024 Andreas Kupries) [//000000006]: # (critcl\_howto\_use\(n\) 3\.3\.1 doc "C Runtime In Tcl \(CriTcl\)")
[ Table Of Contents | Keyword Index ]
# NAME critcl\_howto\_use \- How To Use CriTcl # Table Of Contents - [Table Of Contents](#toc) - [Description](#section1) - [Basics](#section2) - [Simple Arguments](#subsection1) - [Simple Results](#subsection2) - [Range\-limited Simple Arguments](#subsection3) - [String Arguments](#subsection4) - [String Results](#subsection5) - [List Arguments](#subsection6) - [Constrained List Arguments](#subsection7) - [Raw Tcl\_Obj\* Arguments](#subsection8) - [Raw Tcl\_Obj\* Results](#subsection9) - [Errors & Messages](#subsection10) - [Tcl\_Interp\* Access](#subsection11) - [Binary Data Arguments](#subsection12) - [Constant Binary Data Results](#subsection13) - [Tcl Runtime Version](#subsection14) - [Additional Tcl Code](#subsection15) - [Debugging Support](#subsection16) - [Install The Package](#subsection17) - [Using External Libraries](#section3) - [Default Values For Arguments](#subsection18) - [Custom Argument Validation](#subsection19) - [Separating Local C Sources](#subsection20) - [Very Simple Results](#subsection21) - [Structure Arguments](#subsection22) - [Structure Results](#subsection23) - [Structure Types](#subsection24) - [Large Structures](#subsection25) - [External Structures](#subsection26) - [External Enumerations](#subsection27) - [External Bitsets/Bitmaps/Flags](#subsection28) - [Non\-standard header/library locations](#subsection29) - [Non\-standard compile/link configuration](#subsection30) - [Querying the compilation environment](#subsection31) - [Shared C Code](#subsection32) - [Various](#section4) - [Author, License, Description, Keywords](#subsection33) - [Get Critcl Application Help](#subsection34) - [Supported Targets & Configurations](#subsection35) - [Building A Package](#subsection36) - [Building A Package For Debugging](#subsection37) - [Authors](#section5) - [Bugs, Ideas, Feedback](#section6) - [Keywords](#keywords) - [Category](#category) - [Copyright](#copyright) # DESCRIPTION Be welcome to the *C Runtime In Tcl* \(short: *[CriTcl](critcl\.md)*\), a system for embedding and using C code from within [Tcl](http://core\.tcl\-lang\.org/tcl) scripts\. This document assumes the presence of a working *[CriTcl](critcl\.md)* installation\. If that is missing follow the instructions on *[How To Install CriTcl](critcl\_howto\_install\.md)*\. # Basics To create a minimal working package 1. Choose a directory to develop in and make it the working directory\. This should not be a checkout of *[CriTcl](critcl\.md)* itself\. 1. Save the following example to a file\. In the following it is assumed that the file was named "example\.tcl"\. # -*- tcl -*- # Critcl support, absolutely necessary. package require critcl # Bail out early if the compile environment is not suitable. if {![critcl::compiling]} { error "Unable to build project, no proper compiler found." } # Information for the teapot.txt meta data file put into a generated package. # Free form strings. critcl::license {Andreas Kupries} {Under a BSD license} critcl::summary {The first CriTcl-based package} critcl::description { This package is the first example of a CriTcl-based package. It contains all the necessary and conventionally useful pieces. } critcl::subject example {critcl package} critcl::subject {basic critcl} # Minimal Tcl version the package should load into. critcl::tcl 8.6 # Use to activate Tcl memory debugging #critcl::debug memory # Use to activate building and linking with symbols (for gdb, etc.) #critcl::debug symbols # ## #### ######### ################ ######################### ## A hello world, directly printed to stdout. Bypasses Tcl's channel system. critcl::cproc hello {} void { printf("hello world\n"); } # ## #### ######### ################ ######################### # Forcing compilation, link, and loading now. critcl::msg -nonewline { Building ...} if {![critcl::load]} { error "Building and loading the project failed." } # Name and version the package. Just like for every kind of Tcl package. package provide critcl-example 1 1. Invoke the command critcl -keep -debug all -pkg example.tcl This compiles the example and installs it into a "lib/" sub directory of the working directory, generating output similar to Config: linux-x86_64-gcc Build: linux-x86_64-gcc Target: linux-x86_64 Source: example.tcl (provide critcl-example 1) Building ... Library: example.so (tclStubsPtr => const TclStubs *tclStubsPtr;) (tclPlatStubsPtr => const TclPlatStubs *tclPlatStubsPtr;) Package: lib/example Files left in /home/aku/.critcl/pkg2567272.1644845439 during operation\. The __\-keep__ option suppressed the cleanup of the generated C files, object files, compiler log, etc\. normally done at the end of building\. % ls -l /home/aku/.critcl/pkg2567272.1644845439 total 36 -rw-r--r-- 1 aku aku 1260 Feb 14 18:30 v3118_00000000000000000000000000000004.c -rw-r--r-- 1 aku aku 2096 Feb 14 18:30 v3118_00000000000000000000000000000004_pic.o -rw-r--r-- 1 aku aku 1728 Feb 14 18:30 v3118_00000000000000000000000000000009.c -rw-r--r-- 1 aku aku 2448 Feb 14 18:30 v3118_00000000000000000000000000000009_pic.o -rwxr-xr-x 1 aku aku 14424 Feb 14 18:30 v3118_00000000000000000000000000000009.so -rw-r--r-- 1 aku aku 1725 Feb 14 18:30 v3118.log This enables inspection of the generated C code\. Simply drop the option from the command if that is not desired\. The option __\-debug__, with argument __all__ activated Tcl's memory debugging and caused the generation of the symbol tables needed by __gdb__ or any other debugger\. The alternate arguments __memory__ and __symbols__ activate just one of the these\. 1. Now invoke an interactive __tclsh__ and enter the commands: - *lappend auto\_path lib* - *package require critcl\-example* - *info loaded* - *hello* - *exit* I\.e\. extend __tclsh__'s package search path to include the location of the new package, load the package, verify that the associated shared library is present, invoke the package command, and stop the session\. When the package command is invoked the terminal will show __hello world__, followed by the prompt\. Commands: *critcl::compiling*, *critcl::cproc*, *critcl::description*, *critcl::license*, *critcl::load*, *critcl::msg*, *critcl::subject*, *critcl::summary*, *critcl::tcl*\. Make a copy of "example\.tcl" before going through the sub\-sections\. Keep it as a save point to return to from the editing done in the sub\-section\. ## Simple Arguments A function taking neither arguments nor returning results is not very useful\. 1. We are now extending the command to take an argument\. 1. >  Starting from the [Basics](#section2)\. >             Edit the file "example\.tcl"\. >             Remove the definition of __hello__\. Replace it with >     critcl::cproc hello \{double x\} void \{ >  /\* double x; \*/ >  printf\("hello world, we have %f\\n", x\); >     \} and rebuild the package\. 1. When testing the package again, entering the simple __hello__ will fail\. The changed command is now expecting an argument, and we gave it none\. Retry by entering hello 5 instead\. Now the command behaves as expected and prints the provided value\. Further try and enter hello world This will fail again\. The command expected a real number and we gave it something decidedly not so\. These checks \(argument count, argument type\) are implemented in the translation layer *[CriTcl](critcl\.md)* generates for the C function\. The function body is never invoked\. ## Simple Results A function taking neither arguments nor returning results is not very useful\. 1. We are now extending the command to return a result\. 1. >  Starting from the [Basics](#section2)\. >             Edit the file "example\.tcl"\. >             Remove the definition of __hello__\. Replace it with >     critcl::cproc twice \{double x\} double \{ >  return 2\*x; >     \} and rebuild the package\. 1. Note that the name of the command changed\. Goodbye __hello__, hello __twice__\. 1. Invoke twice 4 and the __tclsh__ will print the result __8__ in the terminal\. An important limitation of the commands implemented so far is that they cannot fail\. The types used so far \(__void__, __double__\) and related scalar types can return only a value of the specified type, and nothing else\. They have no ability to signal an error to the Tcl script\. We will come back to this after knowing a bit more about the more complex argument and result types\. Of interest to the eager reader: *[CriTcl cproc Type Reference](critcl\_cproc\.md)* ## Range\-limited Simple Arguments 1. >  Starting from the [Basics](#section2)\. >             Edit the file "example\.tcl"\. >             Remove the definition of __hello__\. Replace it with >     critcl::cproc hello \{\{double > 5 < 22\} x\} void \{ >  /\* double x, range 6\-21; \*/ >  printf\("hello world, we have %f\\n", x\); >     \} and rebuild the package\. 1. When dealing with simple arguments whose range of legal values is limited to a single continuous interval extend the base type with the necessary relations \(__>__, __>=__, __<__, and __<=__\) and limiting values\. *Note* that the limiting values have to be proper constant numbers acceptable by the base type\. Symbolic values are not accepted\. Here the argument *x* of the changed function will reject all values outside of the interval 6 to 21\. ## String Arguments Tcl prides itself on the fact that *Everything Is A String*\. So how are string values passed into C functions ? 1. We are now extending the command with a string argument\. 1. >  Starting from the [Basics](#section2)\. >             Edit the file "example\.tcl"\. >             Remove the definition of __hello__\. Replace it with >     critcl::cproc hello \{pstring x\} void \{ >  /\* critcl\_pstring x \(\.s, \.len, \.o\); \*/ >  printf\("hello world, from %s \(%d bytes\)\\n", x\.s, x\.len\); >     \} and rebuild the package\. 1. Testing __hello__ with any kind of argument the information is printed\. 1. Of note here is that the command argument __x__ is a structure\. 1. The example uses only two of the three fields, the pointer to the string data \(__\.s__\), and the length of the string \(__\.len__\)\. In bytes, *not* in characters, because Tcl's internal representation of strings uses a modified UTF\-8 encoding\. A character consists of between 1 and __TCL\_UTF\_MAX__ bytes\. 1. *Attention* The pointers \(__\.s__\) refer into data structures *internal* to and managed by the Tcl interpreter\. Changing them is highly likely to cause subtle and difficult to track down bugs\. Any and all complex arguments must be treated as *Read\-Only*\. Never modify them\. 1. Use the simpler type __char\*__ if and only if the length of the string is not relevant to the command, i\.e\. not computed, or not used by any of the functions called from the body of the command\. Its value is essentially just the __\.s__ field of __pstring__'s structure\. This then looks like critcl::cproc hello {char* x} void { /* char* x; */ printf("hello world, from %s\n", x); } ## String Results Tcl prides itself on the fact that *Everything Is A String*\. So how are string values returned from C functions ? 1. We are now giving the command a string result\. 1. >  Starting from the [Basics](#section2)\. >             Edit the file "example\.tcl"\. >             Remove the definition of __hello__\. Replace it with >     critcl::cproc twice \{double x\} char\* \{ >  char buf \[lb\]40\[rb\]; >  sprintf\(buf, "%f", 2\*x\); >  return buf; >     \} and rebuild the package\. 1. Note that the name of the command changed\. Goodbye __hello__, hello __twice__\. 1. Invoke twice 4 and the __tclsh__ will print the result __8__ in the terminal\. 1. *Attention*\. To the translation layer the string pointer is owned by the C code\. A copy is made to become the result seen by Tcl\. While the C code is certainly allowed to allocate the string on the heap if it so wishes, this comes with the responsibility to free the string as well\. Abrogation of that responsibility will cause memory leaks\. The type __char\*__ is recommended to be used with static string buffers, string constants and the like\. 1. Conversely, to return heap\-allocated strings it is recommended to use the type __string__ instead\. Replace the definition of __twice__ with critcl::cproc twice {double x} string { char* buf = Tcl_Alloc (40); sprintf(buf, "%f", 2*x); return buf; } Now the translation layer takes ownership of the string from the C code and transfers that ownership to the Tcl interpreter\. This means that the string will be released when the Tcl interpreter is done with it\. The C code has no say in the lifecycle of the string any longer, and having the C code releasing the string *will* cause issues\. Dangling pointers and associated memory corruption and crashes\. ## List Arguments Even as a string\-oriented language Tcl is capable of handling more complex structures\. The first of it, with Tcl since the beginning are *lists*\. Sets of values indexed by a numeric value\. In C parlance, *arrays*\. 1. We are now extending the command with a __list__ argument\. 1. >  Starting from the [Basics](#section2)\. >             Edit the file "example\.tcl"\. >             Remove the definition of __hello__\. Replace it with >     critcl::cproc hello \{list x\} void \{ >  /\* critcl\_list x \(\.o, \.v, \.c\); \*/ >  printf\("hello world, %d elements in \(%s\)\\n", x\.c, Tcl\_GetString \(x\.o\)\); >     \} and rebuild the package\. 1. Testing __hello__ with any kind of list argument it will print basic information about it\. 1. Of note here is that the command argument __x__ is a structure\. 1. The example uses only two of the three fields, the pointer to the original __Tcl\_Obj\*__ holding the list \(__\.o__\), and the length of the list \(__\.c__\) in elements\. The field __\.v__, not used above, is the C array holding the __Tcl\_Obj\*__ pointers to the list elements\. 1. *Attention* The pointers __\.o__ and __\.v__ refer into data structures *internal* to and managed by the Tcl interpreter\. Changing them is highly likely to cause subtle and difficult to track down bugs\. Any and all complex arguments must be treated as *Read\-Only*\. Never modify them\. 1. As a last note, this argument type does not place any constraints on the size of the list, or on the type of the elements\. ## Constrained List Arguments As mentioned at the end of section [List Arguments](#subsection6) the basic __list__ type places no constraints on the size of the list, nor on the type of the elements\. Both kind of constraints can be done however, alone or together\. 1. We are now extending the command with a length\-limited list\. 1. >  Starting from the [Basics](#section2)\. >             Edit the file "example\.tcl"\. >             Remove the definition of __hello__\. Replace it with >     critcl::cproc hello \{\[5\] x\} void \{ >  /\* critcl\_list x \(\.o, \.v, \.c\); \*/ >  printf\("hello world, %d elements in \(%s\)\\n", x\.c, Tcl\_GetString \(x\.o\)\); >     \} and rebuild the package\. 1. Testing the new command will show that only lists holding exactly __5__ elements will be accepted\. 1. To accept lists of any length use __\[\]__ or __\[\*\]__\. Both forms are actually aliases of the base type, i\.e\. __list__\. 1. To constrain just the type of elements, for example to type __int__, use int[] or []int 1. To combine both type and length constraints use the forms int[5] or [5]int 1. The last, most C\-like forms of these contraints place the list indicator syntax on the argument instead of the type\. I\.e int a[] or int a[5] ## Raw Tcl\_Obj\* Arguments When the set of predefined argument types is not enough the oldest way of handling the situation is falling back to the structures used by Tcl to manage values, i\.e\. __Tcl\_Obj\*__\. 1. >  Starting from the [Basics](#section2)\. >             Edit the file "example\.tcl"\. >             Remove the definition of __hello__\. Replace it with >     critcl::cproc hello \{object x\} void \{ >  /\* Tcl\_Obj\* x \*/ >  int len; >  char\* str = Tcl\_GetStringFromObj \(x, &len\); >  printf\("hello world, from %s \(%d bytes\)\\n", str, len\); >     \} and rebuild the package\. 1. Having direct access to the raw __Tcl\_Obj\*__ value all functions of the public Tcl API for working with Tcl values become usable\. The downside of that is that all the considerations for handling them apply as well\. In other words, the C code becomes responsible for handling the reference counts correctly, for duplicating shared __Tcl\_Obj\*__ structures before modifying them, etc\. One thing the C code is allowed to do without restriction is to *shimmer* the internal representation of the value as needed, through the associated Tcl API functions\. For example __Tcl\_GetWideIntFromObj__ and the like\. It actually has to be allowed to do so, as the type checking done as part of such conversions is now the responsibility of the C code as well\. For the predefined types this is all hidden in the translation layer generated by *[CriTcl](critcl\.md)*\. If more than one command has to perform the same kind of checking and/or conversion it is recommended to move the core of the code into proper C functions for proper sharing among the commands\. 1. This is best done by defining a custom argument type using *[CriTcl](critcl\.md)* commands\. This extends the translation layer *[CriTcl](critcl\.md)* is able to generate\. The necessary conversions, type checks, etc\. are then again hidden from the bulk of the application C code\. We will come back to this\. ## Raw Tcl\_Obj\* Results When the set of predefined result types is not enough the oldest way of handling the situation is falling back to the structures used by Tcl to manage values, i\.e\. __Tcl\_Obj\*__\. Two builtin types are provided for this, to handle different reference counting requirements\. 1. >  Starting from the [Basics](#section2)\. >             Edit the file "example\.tcl"\. >             Remove the definition of __hello__\. Replace it with >     critcl::cproc twice \{double x\} object0 \{ >  return Tcl\_NewDoubleObj\(2\*x\); >     \} and rebuild the package\. 1. With __object0__ the translation layer assumes that the returned __Tcl\_Obj\*__ value has a reference count of __0__\. I\.e\. a value which is unowned and unshared\. This value is passed directly to Tcl for its use, without any changes\. Tcl increments the reference count and thus takes ownership\. The value is still unshared\. It would be extremely detrimental if the translation layer had decremented the reference count before passing the value\. This action would release the memory and then leave Tcl with a dangling pointer and the associated memory corruption bug to come\. 1. The situation changes when the C code returns a __Tcl\_Obj\*__ value with a reference count greater than __0__\. I\.e\. at least owned \(by the C code\), and possibly even shared\. There are some object constructors and/or mutators in the public Tcl API which do that, although I do not recall their names\. The example below simulates this situation by explicitly incrementing the reference count before returning the value\. 1. In this case use the type __object__ \(without the trailing __0__\)\. 1. Edit the file "example\.tcl" and replace the definition of __twice__ with critcl::cproc twice {double x} object { Tcl_Obj* result = Tcl_NewDoubleObj(2*x); Tcl_IncrRefCount (result); return result; } and rebuild the package\. 1. After handing the value to Tcl, with the associated incremented reference count, the translation layer decrements the reference count, invalidating the C code's ownership and leaving the final reference count the same\. Note, the order matters\. If the value has only one reference then decrementing it before Tcl increments it would again release the value, and again leave Tcl with a dangling pointer\. Also, not decrementing the reference count at all causes the inverse problem to the memory corruption issues of before, memory leaks\. 1. *Note* that both types transfer ownership of the value\. Their difference is just in the reference count of the value coming out of the function, and the \(non\-\)actions having to be \(not\) taken to effect said transfer without causing memory issues\. ## Errors & Messages 1. >  Starting from the [Basics](#section2)\. >             Edit the file "example\.tcl"\. >             Remove the definition of __hello__\. Replace it with >     critcl::cproc sqrt \{ >  Tcl\_Interp\* interp >  double x >     \} object0 \{ >  if \(x < 0\) \{ >      Tcl\_SetObjResult \(interp, Tcl\_ObjPrintf \("Expected double >=0, but got \\"%d\\"", x\)\); >      Tcl\_SetErrorCode \(interp, "EXAMPLE", "BAD", "DOMAIN", NULL\); >      return NULL; >  \} >  return Tcl\_NewDoubleObj\(sqrt\(x\)\); >     \} and rebuild the package\. 1. In standard C\-based packages commands signal errors by returning __TCL\_ERROR__, placing the error message as the interpreter result, and maybe providing an error code via __Tcl\_SetErrorCode__\. 1. When using __critcl::cproc__ this is limited and hidden\. 1. The simple and string types for results do not allow failure\. The value is returned to the translation layer, converted into the interpreter result and then reported as success \(__TCL\_OK__\)\. 1. The object types on the other hand do allow for failure\. Return a __NULL__ value to signal failure to the translation layer, which then reports this to the interpreter via the standard __TCL\_ERROR__\. 1. *Attention* Setting the desired error message and code into the interpreter is still the responsibility of the function body\. ## Tcl\_Interp\* Access 1. Reread the example in the __previous__ section\. 1. Note the type __Tcl\_Interp\*__ used for the first argument\. 1. This type is special\. 1. An argument of this type has to be the first argument of a function\. 1. Using it tells *[CriTcl](critcl\.md)* that the function needs access to the Tcl interpreter calling it\. It then arranges for that to happen in the generated C code\. Using functions from Tcl's public C API taking an interpreter argument in the function body is a situation where this is needed\. 1. *This special argument is not visible at the script level*\. 1. *This special argument is not an argument of the Tcl command for the function*\. 1. In our example the __sqrt__ command is called with a single argument\. 1. The name of the argument can be freely chosen\. It is the type which is important and triggers the special behaviour\. My prefered names are __ip__ and __interp__\. ## Binary Data Arguments 1. >  Starting from the [Basics](#section2)\. >             Edit the file "example\.tcl"\. >             Remove the definition of __hello__\. Replace it with >     critcl::cproc hello \{bytes x\} void \{ >         /\* critcl\_bytes x \(\.s, \.len, \.o\); \*/ >         printf\("hello world, with %d bytes \\n data: ", x\.len\); >         for \(i = 0; i < x\.len; i\+\+\) \{ >             printf\(" %02x", x\.s\[i\]\); >             if \(i % 16 == 15\) printf \("\\ndata: "\); >         \} >         if \(i % 16 \!= 0\) printf \("\\n"\); >     \} and rebuild the package\. 1. To deal with strings holding binary data use the type __bytes__\. It ensures that the function sees the proper binary data, and not how Tcl is encoding it internally, as the string types would\. ## Constant Binary Data Results 1. Use the command __critcl::cdata__ to create a command taking no arguments and returning a constant ByteArray value\. # P5 3 3 255 \n ... critcl::cdata cross3x3pgm { 80 52 32 51 32 51 32 50 53 53 10 0 255 0 255 255 255 0 255 0 } ## Tcl Runtime Version 1. See and reread the [basic package](#section2) for the introduction of the commands referenced below\. 1. Use the command __critcl::tcl__ to tell *[CriTcl](critcl\.md)* the minimal version of Tcl the package is to be used with\. This determines which Tcl headers all files are compiled against, and what version of the public Tcl API is available to the C code\. Currently __8\.4__, __8\.5__ and __8\.6__ are supported\. If not specified __8\.4__ is assumed\. ## Additional Tcl Code 1. >  Starting from the [Basics](#section2)\. >             Edit the file "example\.tcl"\. >             Remove the definition of __hello__\. Replace it with >     critcl::cproc greetings::hello \{\} void \{ >  printf\("hello world\\n"\); >     \} > >     critcl::cproc greetings::hi \{\} void \{ >  printf\("hi you\\n"\); >     \} and rebuild the package\. 1. The command __hello__ is now available as __greetings::hello__, and a second command __greetings::hi__ was added\. 1. Tcl has automatically created the namespace __greetings__\. 1. Create a file "example\-policy\.tcl" and enter namespace eval greetings { namespace export hello hi namespace ensemble create } into it\. 1. Edit "example\.tcl"\. Add the code critcl::tsources example-policy.tcl and rebuild the package\. 1. The added Tcl code makes __greetings__ available as an *ensemble* command\. The commands in the namespace have been registered as methods of the ensemble\. They can now be invoked as greetings hello greetings hi 1. The Tcl builtin command __string__ is an ensemble as well, as is __clock__\. New commands: *critcl::tsources* ## Debugging Support 1. See and reread the [basic package](#section2) for the introduction of the commands referenced below\. 1. Use the command __critcl::debug__ to activate various features supporting debugging\. critcl::debug memory ;# Activate Tcl memory debugging (-DTCL_MEM_DEBUG) critcl::debug symbols ;# Activate building and linking with debugger symbols (-g) critcl::debug all ;# Shorthand for both `memory` and `symbols`. ## Install The Package 1. Starting from the [Basics](#section2)\. 1. Use an interactive __tclsh__ seesion to determine the value of __info library__\. For the purpose of this HowTo assume that this path is "/home/aku/opt/ActiveTcl/lib/tcl8\.6" 1. Invoke the critcl application in a terminal, using critcl -libdir /home/aku/opt/ActiveTcl/lib/tcl8.6 -pkg example.tcl 1. The package is now build and installed into the chosen directory\. % find /home/aku/opt/ActiveTcl/lib/tcl8.6/example/ /home/aku/opt/ActiveTcl/lib/tcl8.6/example/ /home/aku/opt/ActiveTcl/lib/tcl8.6/example/pkgIndex.tcl /home/aku/opt/ActiveTcl/lib/tcl8.6/example/critcl-rt.tcl /home/aku/opt/ActiveTcl/lib/tcl8.6/example/license.terms /home/aku/opt/ActiveTcl/lib/tcl8.6/example/linux-x86_64 /home/aku/opt/ActiveTcl/lib/tcl8.6/example/linux-x86_64/example.so /home/aku/opt/ActiveTcl/lib/tcl8.6/example/teapot.txt # Using External Libraries To create a minimal package wrapping an external library 1. Choose a directory to develop in and make it the working directory\. This should not be a checkout of *[CriTcl](critcl\.md)* itself\. 1. Save the following example to a file\. In the following it is assumed that the file was named "example\.tcl"\. # -*- tcl -*- # Critcl support, absolutely necessary. package require critcl # Bail out early if the compile environment is not suitable. if {![critcl::compiling]} { error "Unable to build project, no proper compiler found." } # Information for the teapot.txt meta data file put into a generated package. # Free form strings. critcl::license {Andreas Kupries} {Under a BSD license} critcl::summary {The second CriTcl-based package} critcl::description { This package is the second example of a CriTcl-based package. It contains all the necessary and conventionally useful pieces for wrapping an external library. } critcl::subject {external library usage} example {critcl package} critcl::subject {wrapping external library} # Minimal Tcl version the package should load into. critcl::tcl 8.6 # Locations for headers and shared library of the library to wrap. # Required only for non-standard locations, i.e. where CC is not searching by default. critcl::cheaders -I/usr/include critcl::clibraries -L/usr/lib/x86_64-linux-gnu critcl::clibraries -lzstd # Import library API, i.e. headers. critcl::include zstd.h # ## #### ######### ################ ######################### ## (De)compression using Zstd ## Data to (de)compress is passed in and returned as Tcl byte arrays. critcl::cproc compress { Tcl_Interp* ip bytes data int {level ZSTD_CLEVEL_DEFAULT} } object0 { /* critcl_bytes data; (.s, .len, .o) */ Tcl_Obj* error_message; int max = ZSTD_maxCLevel(); if ((level < 1) || (level > max)) { error_message = Tcl_ObjPrintf ("level must be integer between 1 and %d", max); goto err; } size_t dest_sz = ZSTD_compressBound (data.len); void* dest_buf = Tcl_Alloc(dest_sz); if (!dest_buf) { error_message = Tcl_NewStringObj ("can't allocate memory to compress data", -1); goto err; } size_t compressed_size = ZSTD_compress (dest_buf, dest_sz, data.s, data.len, level); if (ZSTD_isError (compressed_size)) { Tcl_Free(dest_buf); error_message = Tcl_ObjPrintf ("zstd encoding error: %s", ZSTD_getErrorName (compressed_size)); goto err; } Tcl_Obj* compressed = Tcl_NewByteArrayObj (dest_buf, compressed_size); Tcl_Free (dest_buf); return compressed; err: Tcl_SetObjResult (ip, error_message); return 0; } critcl::cproc decompress { Tcl_Interp* ip bytes data } object0 { Tcl_Obj* error_message; size_t dest_sz = ZSTD_getDecompressedSize (data.s, data.len); if (dest_sz == 0) { error_message = Tcl_NewStringObj("invalid data", -1); goto err; } void* dest_buf = Tcl_Alloc (dest_sz); if (!dest_buf) { error_message = Tcl_NewStringObj("failed to allocate decompression buffer", -1); goto err; } size_t decompressed_size = ZSTD_decompress (dest_buf, dest_sz, data.s, data.len); if (decompressed_size != dest_sz) { Tcl_Free (dest_buf); error_message = Tcl_ObjPrintf("zstd decoding error: %s", ZSTD_getErrorName (decompressed_size)); goto err; } Tcl_Obj* decompressed = Tcl_NewByteArrayObj (dest_buf, dest_sz); Tcl_Free (dest_buf); return decompressed; err: Tcl_SetObjResult (ip, error_message); return 0; } # ## #### ######### ################ ######################### # Forcing compilation, link, and loading now. critcl::msg -nonewline { Building ...} if {![critcl::load]} { error "Building and loading the project failed." } # Name and version the package. Just like for every kind of Tcl package. package provide critcl-example 1 1. Build the package\. See the __Basics__, if necessary\. 1. Load the package and invoke the commands\. *Attention*\. The commands take and return binary data\. This may look very bad in the terminal\. 1. To test the commands enter set a [compress {hhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhello wwwwwwwworld}] decompress $a in the interactive __tclsh__ New commands: *critcl::cheaders*, *critcl::clibraries*, *critcl::include*\. ## Default Values For Arguments 1. Reread the example of the main section\. Note specifically the line int {level ZSTD_CLEVEL_DEFAULT} 1. This line demonstrates that __critcl::cproc__ arguments allowed to have default values, in the same vein as __proc__ arguments, and using the same syntax\. 1. *Attention* Default values have to be legal C rvalues and match the C type of the argument\. They are literally pasted into the generated C code\. They bypass any argument validation done in the generated translation layer\. This means that it is possible to use a value an invoker of the command cannot use from Tcl\. 1. This kind of in\-band signaling of a default versus a regular argument is however not necessary\. Look at critcl::cproc default_or_not {int {x 0}} void { if !has_x { printf("called with default\n"); return } printf("called with %d\n", x); } Any argument *x* with a default causes *[CriTcl](critcl\.md)* to create a hidden argument *has\_x*, of type int \(boolean\)\. This argument is set to __1__ when *x* was filled from defaults, and __0__ else\. ## Custom Argument Validation 1. Starting from the [base wrapper](#section3)\. Edit the file "example\.tcl"\. Replace the entire __compress__ function with critcl::argtype zstd_compression_level { /* argtype: `int` */ if (Tcl_GetIntFromObj (interp, @@, &@A) != TCL_OK) return TCL_ERROR; /* additional validation */ int max = ZSTD_maxCLevel(); if ((@A < 1) || (@A > max)) { Tcl_SetObjResult (interp, Tcl_ObjPrintf ("zstd compression level must be integer between 1 and %d", max)); return TCL_ERROR; } /* @@: current objv[] element ** @A: name of argument variable for transfer to C function ** interp: predefined variable, access to current interp - error messages, etc. */ } int int ;# C types of transfer variable and function argument. critcl::cproc compress { Tcl_Interp* ip bytes data zstd_compression_level {level ZSTD_CLEVEL_DEFAULT} } object0 { /* critcl_bytes data; (.s, .len, .o) */ /* int level; validated to be in range 1...ZSTD_maxCLevel() */ Tcl_Obj* error_message; size_t dest_sz = ZSTD_compressBound (data.len); void* dest_buf = Tcl_Alloc(dest_sz); if (!dest_buf) { error_message = Tcl_NewStringObj ("can't allocate memory to compress data", -1); goto err; } size_t compressed_size = ZSTD_compress (dest_buf, dest_sz, data.s, data.len, level); if (ZSTD_isError (compressed_size)) { Tcl_Free(dest_buf); error_message = Tcl_ObjPrintf ("zstd encoding error: %s", ZSTD_getErrorName (compressed_size)); goto err; } Tcl_Obj* compressed = Tcl_NewByteArrayObj (dest_buf, compressed_size); Tcl_Free (dest_buf); return compressed; err: Tcl_SetObjResult (ip, error_message); return 0; } and rebuild the package\. In the original example the *level* argument of the function was validated in the function itself\. This may detract from the funtionality of interest itself, especially if there are lots of arguments requiring validation\. If the same kind of argument is used in multiple places this causes code duplication in the functions as well\. Use a custom argument type as defined by the modification to move this kind of validation out of the function, and enhance readability\. Code duplication however is only partially adressed\. While there is no duplication in the visible definitions the C code of the new argument type is replicated for each use of the type\. 1. Now replace the __argtype__ definition with critcl::code { int GetCompressionLevel (Tcl_Interp* interp, Tcl_Obj* obj, int* level) { if (Tcl_GetIntFromObj (interp, obj, level) != TCL_OK) return TCL_ERROR; int max = ZSTD_maxCLevel(); if ((*level < 1) || (*level > max)) { Tcl_SetObjResult (interp, Tcl_ObjPrintf ("zstd compression level must be integer between 1 and %d", max)); return TCL_ERROR; } return TCL_OK; } } critcl::argtype zstd_compression_level { if (GetCompressionLevel (@@, &@A) != TCL_OK) return TCL_ERROR; } int int and rebuild the package\. Now only the calls to the new validation function are replicated\. The function itself exists only once\. ## Separating Local C Sources 1. Starting from the end of the [previous](#subsection19) section\. Edit the file "example\.tcl"\. 1. Save the contents of the __critcl::ccode__ block into a file "example\.c" and then replace the entire block with critcl::csources example.c critcl::ccode { extern int GetCompressionLevel (Tcl_Interp* interp, Tcl_Obj* obj, int* level); } When mixing C and Tcl code the different kind of indentation rules for these languages may come into strong conflict\. Further, very large blocks of C code may reduce overall readability\. 1. The examples fixes this by moving the code block into a local C file and then registering this file with *[CriTcl](critcl\.md)*\. When building the package *[CriTcl](critcl\.md)* arranges to build all such registered C files as well\. 1. *Attention*\. The C code is now in a separate compilation unit\. The example declares the exported function so that the __cproc__s are again able to see and use it\. 1. Now go a step further\. Save the declaration into a file "example\.h", and then use critcl::include example.h to import it\. Note that this is just a shorthand for critcl::ccode { #include "example.h" } 1. As an alternative solution, start from the beginning of the section and move the entire original __critcl::ccode__ block into a file "example\-check\.tcl"\. Then replace it with critcl::source example-check.tcl to import it into the main code again\. *Attention* Tcl's builtin command __source__ is *not suitable* for importing the separate file due to how *[CriTcl](critcl\.md)* uses the information from __info script__ to key various internal datastructures\. ## Very Simple Results 1. Starting from the end of the [validation](#subsection19) section\. Edit the file "example\.tcl"\. Add the code below, just before the __compress__ command\. critcl::cconst version char* ZSTD_VERSION_STRING critcl::cconst min-level int 1 critcl::cconst max-level int ZSTD_maxCLevel() and rebuild the package\. 1. These declarations create three additional commands, each returning the specified value\. A fixed string, an integer, and a function call returning an integer\. 1. *Attention* The values have to be legal C rvalues and match the C type of the result\. They are literally pasted into the generated C code\. 1. When using __critcl::cconst__ *[CriTcl](critcl\.md)* is aware that the result of the function does not depend on any parameters and is computed in a single C expression\. This enables it do to away with the internal helper function it would need and generate if __critcl::cproc__ had been used instead\. For example critcl::cproc version {} char* { return ZSTD_VERSION_STRING; } ## Structure Arguments 1. For all that this is a part of how to [Use External Libraries](#section3), for the demonstratation only the basics are needed\. 1. >  Starting from the [Basics](#section2)\. >             Edit the file "example\.tcl"\. >             Remove the definition of __hello__\. Replace it with >     critcl::ccode \{ >  typedef struct vec2 \{ >      double x; >      double y; >  \} vec2; > >  typedef vec2\* vec2ptr; > >  int >  GetVecFromObj \(Tcl\_Interp\* interp, Tcl\_Obj\* obj, vec2ptr\* vec\) >  \{ >      int len; >      if \(Tcl\_ListObjLength \(interp, obj, &len\) \!= TCL\_OK\) return TCL\_ERROR; >      if \(len \!= 2\) \{ >   Tcl\_SetObjResult \(interp, Tcl\_ObjPrintf \("Expected 2 elements, got %d", len\)\); >   return TCL\_ERROR; >      \} > >      Tcl\_Obj\* lv\[2\]; >      if \(Tcl\_ListObjGetElements \(interp, obj, &lv\) \!= TCL\_OK\) return TCL\_ERROR; > >      double x, y; >      if \(Tcl\_GetDoubleFromObj \(interp, lv\[0\], &x\) \!= TCL\_OK\) return TCL\_ERROR; >      if \(Tcl\_GetDoubleFromObj \(interp, lv\[1\], &y\) \!= TCL\_OK\) return TCL\_ERROR; > >      \*vec = Tcl\_Alloc \(sizeof \(vec2\)\); >      \(\*vec\)\->x = x; >      \(\*vec\)\->y = y; >      return TCL\_OK; >  \} >     \} > >     critcl::argtype vec2 \{ >  if \(GetVecFromObj \(interp, @@, &@A\) \!= TCL\_OK\) return TCL\_ERROR; >     \} vec2ptr vec2ptr > >     critcl::argtyperelease vec2 \{ >  /\* @A : C variable holding the data to release \*/ >  Tcl\_Free \(\(char\*\) @A\); >     \} > >     critcl::cproc norm \{vec2 vector\} double \{ >  double norm = hypot \(vector\->x, vector\->y\); >  return norm; >     \} and rebuild the package\. 1. The structure to pass as argument is a 2\-dimensional vector\. It is actually passed in as a pointer to a __vec2__ structure\. This pointer is created by the __GetVecFromObj__ function\. It allocates and fills the structure from the Tcl value, which has to be a list of 2 doubles\. The bulk of the code in __GetVecFromObj__ is for verifying this and extracting the doubles\. 1. The __argtyperelease__ code releases the pointer when the C function returns\. In other words, the pointer to the structure is owned by the translation layer and exists only while the function is active\. 1. While working this code has two disadvantages\. First there is memory churn\. Each call of __norm__ causes the creation and release of a temporary __vec2__ structure for the argument\. Second is the need to always extract the data from the __Tcl\_Obj\*__ value\. Both can be done better\. We will come back to this after explaining how to return structures to Tcl\. ## Structure Results 1. Starting from the end of the [previous](#subsection22) section\. 1. Edit the file "example\.tcl" and add the following code, just after the definition of the __norm__ command\. critcl::resulttype vec2 { /* rv: result value of function, interp: current Tcl interpreter */ if (rv == NULL) return TCL_ERROR; Tcl_Obj* lv[2]; lv[0] = Tcl_NewDoubleObj (rv->x); lv[1] = Tcl_NewDoubleObj (rv->y); Tcl_SetObjResult (interp, Tcl_NewListObj (2, lv)); Tcl_Free (rv); return TCL_OK; } vec2ptr ;# C result type critcl::cproc add {vec2 a vec2 b} vec2 { vec2ptr z = Tcl_Alloc (sizeof (vec2)); z->x = a->x + b->x; z->y = a->y + b->y; return z; } and rebuild the package\. 1. The new command __add__ takes two vectors and return the element\-wise sum of both as a new vector\. 1. The function allocates and initializes a structure and hands it over to the translation layer\. Which in turn constructs a Tcl list of 2 doubles from it, sets that as the command's result and at last discards the allocated structure again\. 1. While working this code has two disadvantages\. First there is memory churn\. Each call of __add__ causes the creation and release of three temporary __vec2__ structures\. One per argument, and one for the result\. Second is the need to always construct a complex __Tcl\_Obj\*__ value from the structure\. Both can be done better\. This is explained in the next section\. ## Structure Types 1. Starting from the end of the previous section\. 1. Edit the file "example\.tcl"\. 1. Remove the entire functionality \(type definitions, related C code, and cprocs\)\. Replace it with critcl::ccode { typedef struct vec2 { double x; double y; } vec2; typedef vec2* vec2ptr; /* -- Core vector structure management -- */ static vec2ptr Vec2New (double x, double y) { vec2ptr vec = Tcl_Alloc (sizeof (vec2)); vec->x = x; vec->y = y; return vec; } static vec2ptr Vec2Copy (vec2ptr src) { vec2ptr vec = Tcl_Alloc (sizeof (vec2)); *vec = *src return vec; } static void Vec2Release (vec2ptr vec) { Tcl_Free ((char*) vec); } /* -- Tcl value type for vec2 -- Tcl_ObjType -- */ static void Vec2Free (Tcl_Obj* obj); static void Vec2StringOf (Tcl_Obj* obj); static void Vec2Dup (Tcl_Obj* obj, Tcl_Obj* dst); static int Vec2FromAny (Tcl_Interp* interp, Tcl_Obj* obj); Tcl_ObjType vec2_objtype = { "vec2", Vec2Free, Vec2Dup, Vec2StringOf, Vec2FromAny }; static void Vec2Free (Tcl_Obj* obj) { Vec2Release ((vec2ptr) obj->internalRep.otherValuePtr); } static void Vec2Dup (Tcl_Obj* obj, Tcl_Obj* dst) { vec2ptr vec = (vec2ptr) obj->internalRep.otherValuePtr; dst->internalRep.otherValuePtr = Vec2Copy (vec); dst->typePtr = &vec2_objtype; } static void Vec2StringOf (Tcl_Obj* obj) { vec2ptr vec = (vec2ptr) obj->internalRep.otherValuePtr; /* Serialize vector data to string (list of two doubles) */ Tcl_DString ds; Tcl_DStringInit (&ds); char buf [TCL_DOUBLE_SPACE]; Tcl_PrintDouble (0, vec->x, buf); Tcl_DStringAppendElement (&ds, buf); Tcl_PrintDouble (0, vec->y, buf); Tcl_DStringAppendElement (&ds, buf); int length = Tcl_DStringLength (ds); /* Set string representation */ obj->length = length; obj->bytes = Tcl_Alloc(length+1); memcpy (obj->bytes, Tcl_DStringValue (ds), length); obj->bytes[length] = '\0'; /* ** : package require critcl::cutil ;# get C utilities ** : critcl::cutil::alloc ;# Activate allocation utilities ** : (Internally cheaders, include) ** : Then all of the above can be written as STREP_DS (obj, ds); ** : STREP_DS = STRing REP from DString */ Tcl_DStringFree (&ds); } static int Vec2FromAny (Tcl_Interp* interp, Tcl_Obj* obj) { /* Change intrep of obj to vec2 structure. ** A Tcl list of 2 doubles is used as an intermediary intrep. */ int len; if (Tcl_ListObjLength (interp, obj, &len) != TCL_OK) return TCL_ERROR; if (len != 2) { Tcl_SetObjResult (interp, Tcl_ObjPrintf ("Expected 2 elements, got %d", len)); return TCL_ERROR; } Tcl_Obj* lv[2]; if (Tcl_ListObjGetElements (interp, obj, &lv) != TCL_OK) return TCL_ERROR; double x, y; if (Tcl_GetDoubleFromObj (interp, lv[0], &x) != TCL_OK) return TCL_ERROR; if (Tcl_GetDoubleFromObj (interp, lv[1], &y) != TCL_OK) return TCL_ERROR; obj->internalRep.otherValuePtr = (void*) Vec2New (x, y); obj->typePtr = &vec2_objtype; return TCL_OK; } /* -- (un)packing structures from/into Tcl values -- */ int GetVecFromObj (Tcl_Interp* interp, Tcl_Obj* obj, vec2ptr* vec) { if (obj->typePtr != &vec2_objtype) { if (Vec2FromAny (interp, obj) != TCL_OK) return TCL_ERROR; } *vec = (vec2ptr) obj->internalRep.otherValuePtr; return TCL_OK; } Tcl_Obj* NewVecObj (vec2ptr vec) { Tcl_Obj* obj = Tcl_NewObj (); Tcl_InvalidateStringRep (obj); obj->internalRep.otherValuePtr = Vec2Copy (vec); obj->typePtr = &vec2_objtype; return obj; } } critcl::argtype vec2 { if (GetVecFromObj (interp, @@, &@A) != TCL_OK) return TCL_ERROR; } vec2ptr vec2ptr critcl::resulttype vec2 { /* rv: result value of function, interp: current Tcl interpreter */ Tcl_SetObjResult (interp, NewVecObj (&rv)); return TCL_OK; } vec2 critcl::cproc norm {vec2 vector} double { double norm = hypot (vector->x, vector->y); return norm; } critcl::cproc add {vec2 a vec2 b} vec2 { vec2 z; z.x = a->x + b->x; z.y = a->y + b->y; return z; } and rebuild the package\. 1. This implements a new __Tcl\_ObjType__ to handle __vec2__ structures\. With it __vec2__ structures are become usable as internal representation \(*intrep* of __Tcl\_Obj\*__ values\. The two functions __NewVecObj__ and __GetVecFromObj__ pack and unpack the structures from and into __Tcl\_Obj\*__ values\. The latter performs the complex deserialization into a structure if and only if needed, i\.e\. when the __TclObj\*__ value has no intrep, or the intrep for a different type\. This process of changing the intrep of a Tcl value is called *shimmering*\. Intreps cache the interpretation of __Tcl\_Obj\*__ values as a specific kind of type\. Here __vec2__\. This reduces conversion effort and memory churn, as intreps are kept by the Tcl interpreter as long as possible and needed\. 1. The arguments of __norm__ and __add__ are now converted once on entry, if not yet in the proper type, or not at all, if so\. 1. *Attention*\. This example has the issue of passing result structures by value through the stack, and then packing a copy into a __Tcl\_Obj\*__ value\. While this is no trouble for structures as small as __vec2__ larger structures may pose a problem\. We will address this in the next section\. Packages: *[critcl::cutil](critcl\_cutil\.md)* ## Large Structures 1. Starting from the end of the previous section\. 1. Edit the file "example\.tcl"\. 1. Describing each individual change is too complex\. The following is easier\. 1. Save the file, then replace the entire functionality with the following\. 1. After that use a __diff__ of your choice to compare the files and see the critical changes\. critcl::ccode { typedef struct vec2 { unsigned int rc; double x; double y; } vec2; typedef vec2* vec2ptr; /* -- Core vector structure management -- */ static vec2ptr Vec2New (double x, double y) { vec2ptr vec = Tcl_Alloc (sizeof (vec2)); vec->rc = 0; vec->x = x; vec->y = y; return vec; } static vec2ptr Vec2Copy (vec2ptr src) { scr->rc ++; return src; } static void Vec2Release (vec2ptr vec) { if (vec->rc > 1) { vec->rc --; return; } Tcl_Free ((char*) vec); } /* -- Vector obj type -- */ static void Vec2Free (Tcl_Obj* obj); static void Vec2StringOf (Tcl_Obj* obj); static void Vec2Dup (Tcl_Obj* obj, Tcl_Obj* dst); static int Vec2FromAny (Tcl_Interp* interp, Tcl_Obj* obj); Tcl_ObjType vec2_objtype = { "vec2", Vec2Free, Vec2Dup, Vec2StringOf, Vec2FromAny }; static void Vec2Free (Tcl_Obj* obj) { Vec2Release ((vec2ptr) obj->internalRep.otherValuePtr); } static void Vec2Dup (Tcl_Obj* obj, Tcl_Obj* dst) { vec2ptr vec = (vec2ptr) obj->internalRep.otherValuePtr; dst->internalRep.otherValuePtr = Vec2Copy (vec); dst->typePtr = &vec2_objtype; } static void Vec2StringOf (Tcl_Obj* obj) { vec2ptr vec = (vec2ptr) obj->internalRep.otherValuePtr; /* Serialize vector data to string (list of two doubles) */ Tcl_DString ds; Tcl_DStringInit (&ds); char buf [TCL_DOUBLE_SPACE]; Tcl_PrintDouble (0, vec->x, buf); Tcl_DStringAppendElement (&ds, buf); Tcl_PrintDouble (0, vec->y, buf); Tcl_DStringAppendElement (&ds, buf); int length = Tcl_DStringLength (ds); /* Set string representation */ obj->length = length; obj->bytes = Tcl_Alloc(length+1); memcpy (obj->bytes, Tcl_DStringValue (ds), length); obj->bytes[length] = '\0'; /* ** : package require critcl::cutil ;# get C utilities ** : critcl::cutil::alloc ;# Activate allocation utilities ** : (Internally cheaders, include) ** : Then all of the above can be written as STREP_DS (obj, ds); ** : STREP_DS = STRing REP from DString */ Tcl_DStringFree (&ds); } static int Vec2FromAny (Tcl_Interp* interp, Tcl_Obj* obj) { /* Change internal rep of obj to vector structure. ** A Tcl list of 2 doubles is used as intermediary int rep. */ int len; if (Tcl_ListObjLength (interp, obj, &len) != TCL_OK) return TCL_ERROR; if (len != 2) { Tcl_SetObjResult (interp, Tcl_ObjPrintf ("Expected 2 elements, got %d", len)); return TCL_ERROR; } Tcl_Obj* lv[2]; if (Tcl_ListObjGetElements (interp, obj, &lv) != TCL_OK) return TCL_ERROR; double x, y; if (Tcl_GetDoubleFromObj (interp, lv[0], &x) != TCL_OK) return TCL_ERROR; if (Tcl_GetDoubleFromObj (interp, lv[1], &y) != TCL_OK) return TCL_ERROR; obj->internalRep.otherValuePtr = (void*) Vec2New (x, y); obj->typePtr = &vec2_objtype; return TCL_OK; } /* (un)packing structures from/into Tcl values -- */ int GetVecFromObj (Tcl_Interp* interp, Tcl_Obj* obj, vec2ptr* vec) { if (obj->typePtr != &vec2_objtype) { if (VecFromAny (interp, obj) != TCL_OK) return TCL_ERROR; } *vec = (vec2ptr) obj->internalRep.otherValuePtr; return TCL_OK; } Tcl_Obj* NewVecObj (vec2ptr vec) { Tcl_Obj* obj = Tcl_NewObj (); Tcl_InvalidateStringRep (obj); obj->internalRep.otherValuePtr = Vec2Copy (vec); obj->typePtr = &vec2_objtype; return obj; } } critcl::argtype vec2 { if (GetVecFromObj (interp, @@, &@A) != TCL_OK) return TCL_ERROR; } vec2ptr vec2ptr critcl::resulttype vec2 { /* rv: result value of function, interp: current Tcl interpreter */ Tcl_SetObjResult (interp, NewVecObj (rv)); return TCL_OK; } vec2ptr critcl::cproc norm {vec2 vector} double { double norm = hypot (vector->x, vector->y); return norm; } critcl::cproc add {vec2 a vec2 b} vec2 { return Vec2New (a->x + b->x, a->y + b->y); } 1. The __vec2__ structure is now reference counted\. 1. The core management functions, i\.e\. __Vec2New__, __Vec2Copy__, and __Vec2Release__ are changed to maintain that reference count\. Starting at __0__ on creation, copies increment, and releases decrement\. A structure is actually only freed when its reference count falls to __0__ or below\. 1. __vec2__ results are changed to pointers, easily passed back through the stack\. The modified translation layer just wraps it into a __Tcl\_Obj\*__ value\. 1. *Attention*\. Duplicating such a __Tcl\_Obj\*__ does not duplicate the referenced __vec2__ structure anymore, just adds a reference\. 1. Regarding __diff__ commands, I know of two graphical diffs for Tcl/Tk, [TkDiff](https://tkdiff\.sourceforge\.io), and [Eskil](http://eskil\.tcl\.tk)\. Packages: *[critcl::cutil](critcl\_cutil\.md)* ## External Structures 1. Handle structures provided by external libraries using either [Structure Types](#subsection24) or [Large Structures](#subsection25) as template\. 1. *Attention*\. The choice is with the developer\. This is true even if the external structure is not reference counted by itself\. To reference count a structure __S__ without such simply wrap __S__ into a local structure which provides the reference count and has a field for __S__ \(pointer or value\)\. 1. *Attention* Opaque external types, i\.e\. pointers to structures with hidden fields, can also be handled by the given templates\. ## External Enumerations This section demonstrates how to convert from any kind of enumeration provided by an external library to Tcl strings, and the converse\. 1. For all that this is a part of how to [Use External Libraries](#section3), for the demonstratation only the basics are needed\. 1. >  Starting from the [Basics](#section2)\. >             Edit the file "example\.tcl"\. >             Remove the definition of __hello__\. Replace it with >     package require critcl::emap > >     \# no header included due to use of literal ints instead of symbolic names > >     critcl::emap::def yaml\_sequence\_style\_t \{ >  any 0 >  block 1 >  flow 2 >     \} > >     \# encode: style to int >     critcl::cproc encode \{yaml\_sequence\_style\_t style\} int \{ >  return style; >     \} > >     \# decode: int to style >     critcl::cproc decode \{int style\} yaml\_sequence\_style\_t \{ >  return style; >     \} and rebuild the package\. 1. The map converts between the Tcl level strings listed on the left side to the C values on the right side, and the reverse\. 1. It automatically generates __critcl::argtype__ and __critcl::resulttype__ definitions\. 1. *Attention* Like the default values for __cproc__ arguments, and the results for __cconst__ definitions the values on the right side have to be proper C rvalues\. They have to match C type __int__\. In other words, it is perfectly ok to use the symbolic names provided by the header file of the external library\. *Attention* This however comes at a loss in efficiency\. As *[CriTcl](critcl\.md)* then has no insight into the covered range of ints, gaps, etc\. it has to perform a linear search when mapping from C to Tcl\. When it knows the exact integer values it can use a table lookup instead\. *Attention* It also falls back to a search if a lookup table would contain more than 50 entries\. Packages: *[critcl::emap](critcl\_emap\.md)* ## External Bitsets/Bitmaps/Flags This section demonstrates how to convert from any kind of bit\-mapped flags provided by an external library to lists of Tcl strings, and the converse\. 1. For all that this is a part of how to [Use External Libraries](#section3), for the demonstratation only the basics are needed\. 1. >  Starting from the [Basics](#section2)\. >             Edit the file "example\.tcl"\. >             Remove the definition of __hello__\. Replace it with >     \# http://man7\.org/linux/man\-pages/man7/inotify\.7\.html >      >     package require critcl::bitmap > >     \# critcl::cheaders \- n/a, header is in system directories >     critcl::include sys/inotify\.h >      >     critcl::bitmap::def tcl\_inotify\_events \{ >  accessed IN\_ACCESS >  all IN\_ALL\_EVENTS >  attribute IN\_ATTRIB >  closed IN\_CLOSE >  closed\-nowrite IN\_CLOSE\_NOWRITE >  closed\-write IN\_CLOSE\_WRITE >  created IN\_CREATE >  deleted IN\_DELETE >  deleted\-self IN\_DELETE\_SELF >  dir\-only IN\_ONLYDIR >  dont\-follow IN\_DONT\_FOLLOW >  modified IN\_MODIFY >  move IN\_MOVE >  moved\-from IN\_MOVED\_FROM >  moved\-self IN\_MOVE\_SELF >  moved\-to IN\_MOVED\_TO >  oneshot IN\_ONESHOT >  open IN\_OPEN >  overflow IN\_Q\_OVERFLOW >  unmount IN\_UNMOUNT >     \} \{ >  all closed move oneshot >     \} >      >     \# encode: flag set to int >     critcl::cproc encode \{tcl\_inotify\_events e\} int \{ >  return e; >     \} > >     \# decode: int to flag set >     critcl::cproc decode \{int e\} tcl\_inotify\_events \{ >  return e; >     \} and rebuild the package\. 1. The map converts between lists of the Tcl level strings listed on the left side to the bit\-union of the C values on the right side, and the reverse\. It is noted that the four strings __all__, __closed__, __move__, and __oneshot__ cannot be converted from C flags to list of strings, only from list to bits\. 1. It automatically generates __critcl::argtype__ and __critcl::resulttype__ definitions\. 1. *Attention* Like the default values for __cproc__ arguments, and the results for __cconst__ definitions the values on the right side have to be proper C rvalues\. They have to match C type __int__\. In other words, it is perfectly ok to use the symbolic names provided by the header file of the external library\. As shown\. Packages: *[critcl::bitmap](critcl\_bitmap\.md)* ## Non\-standard header/library locations 1. See and reread the [basic wrapper package](#section3) for the introduction of the commands referenced below\. 1. *Attention* Relative paths will be resolved relative to the location of the "\.tcl" file containing the *[CriTcl](critcl\.md)* commands\. 1. Use the command __critcl::cheaders__ to tell *[CriTcl](critcl\.md)* about non\-standard locations for header files\. Multiple arguments are allowed, and multiple calls as well\. The information accumulates\. Arguments of the form "\-Idirectory" register the directory directly\. For arguments of the form "path" the directory holding the path is registered\. In other words, it is assumed to be the full path of a header *file*, and not a directory\. critcl::cheaders -I/usr/local/include critcl::cheaders local/types.h critcl::cheaders other-support/*.h 1. Use the command __critcl::include__ to actually use a specific header file\. 1. Use the command __critcl::clibraries__ to tell *[CriTcl](critcl\.md)* about non\-standard locations for shared libaries, and about shared libaries to link to Multiple arguments are allowed, and multiple calls as well\. The information accumulates\. Arguments of the form "\-Ldirectory" register a directory\. Arguments of the form "\-lname" register a shared libary to link to by name\. The library will be looked for in both standard and registered directories\. Arguments of the form "\-path" register a shared libary to link to by full path\. critcl::clibraries -L/usr/lib/x86_64-linux-gnu critcl::clibraries -lzstd critcl::clibraries /usr/lib/x86_64-linux-gnu/libzstd.so 1. On Mac OS X use the command __critcl::framework__ to name the frameworks to use in the package\. *Attention* Using the command on other platforms is ok, and will be ignored\. 1. Not answered in the above is how to find the necessary paths if they are not fixed across machines or platforms\. We will come back to this\. ## Non\-standard compile/link configuration 1. See and reread the [basic wrapper package](#section3) for the introduction of the commands referenced below\. 1. Use the command __critcl::cflags__ to provide additional, non\-standard flags to the compiler\. critcl::cflags -DBYTE_ORDER=bigendian 1. Use the command __critcl::ldflags__ to provide additional, non\-standard flags to the linker\. critcl::ldflags - 1. Not answered in the above is how to determine such flags if they are not fixed across machines or platforms\. This is addressed by the next section\. ## Querying the compilation environment 1. Use the command __critcl::check__ to immediately check if a piece of C code can compiled successfully as a means of querying the compiler configuration itself\. if {[critcl::check { #include }]} { Do stuff with FOO.h present. } else { Do stuff without FOO.h } All header and library paths which were registered with *[CriTcl](critcl\.md)* before using __critcl::check__ take part in the attempted compilation\. Use the package __[critcl::util](critcl\_util\.md)__ and various convenience commands it provides\. 1. Use the full *Power of Tcl \(tm\)* itself\. ## Shared C Code 1. See and reread the [basic wrapper package](#section3) for the introduction of the commands referenced below\. 1. Use the command __critcl::ccode__ to write C code residing outside of __cproc__ bodies\. 1. Or, alternatively, place the C code into one or more "\.c" files and use the command __critcl::csources__ to register them with *[CriTcl](critcl\.md)* for compilation\. 1. This topic is also treated in section [Separating Local C Sources](#subsection20)\. # Various ## Author, License, Description, Keywords 1. See and reread the [basic package](#section2) for the introduction of the commands referenced below\. 1. Use the command __critcl::license__ to set the package license\. Use the same command to set the package author\. Both arguments are free form text\. 1. Use the command __critcl::summary__ to set a short package description\. 1. Use the command __critcl::description__ to set a longer package description\. The arguments of both commands are free form text\. 1. Use the command __critcl::subject__ to set one or more keywords\. *Attention* Contrary to the other commands the arguments accumulate\. 1. All the commands are optional\. 1. Their information is not placed into the generated C code\. 1. In *package mode* the information is placed into the file "teapot\.txt" of the generated package\. 1. This file serves as integration point for *Teapot*, the package system of *ActiveTcl*\. ## Get Critcl Application Help 1. Invoke the command critcl -help in a terminal to get help about the __[critcl](critcl\.md)__ application\. ## Supported Targets & Configurations 1. Invoke the application as critcl -show in a terminal to get the detailed configuration of the target for the current platform\. 1. Invoke the application as critcl -show -target NAME in a terminal to get the detailed configuration of the named target\. 1. Invoke the application as critcl -targets in a terminal to get a list of the available targets\. ## Building A Package 1. Start at section [Basics](#section2)\. ## Building A Package For Debugging 1. Start at section [Basics](#section2)\. # Authors Jean Claude Wippler, Steve Landers, Andreas Kupries # Bugs, Ideas, Feedback This document, and the package it describes, will undoubtedly contain bugs and other problems\. Please report them at [https://github\.com/andreas\-kupries/critcl/issues](https://github\.com/andreas\-kupries/critcl/issues)\. Ideas for enhancements you may have for either package, application, and/or the documentation are also very welcome and should be reported at [https://github\.com/andreas\-kupries/critcl/issues](https://github\.com/andreas\-kupries/critcl/issues) as well\. # KEYWORDS [C code](\.\./index\.md\#c\_code), [Embedded C Code](\.\./index\.md\#embedded\_c\_code), [calling C code from Tcl](\.\./index\.md\#calling\_c\_code\_from\_tcl), [code generator](\.\./index\.md\#code\_generator), [compile & run](\.\./index\.md\#compile\_run), [compiler](\.\./index\.md\#compiler), [dynamic code generation](\.\./index\.md\#dynamic\_code\_generation), [dynamic compilation](\.\./index\.md\#dynamic\_compilation), [generate package](\.\./index\.md\#generate\_package), [linker](\.\./index\.md\#linker), [on demand compilation](\.\./index\.md\#on\_demand\_compilation), [on\-the\-fly compilation](\.\./index\.md\#on\_the\_fly\_compilation) # CATEGORY Glueing/Embedded C code # COPYRIGHT Copyright © Jean\-Claude Wippler Copyright © Steve Landers Copyright © 2011\-2024 Andreas Kupries