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diff --git a/doc/sources/libguile-tools.texi b/doc/sources/libguile-tools.texi new file mode 100644 index 000000000..d434406e9 --- /dev/null +++ b/doc/sources/libguile-tools.texi @@ -0,0 +1,191 @@ +@node Tools to automate adding libraries +@chapter Tools to automate adding libraries + +You want to ... + +The chapters @ref{Libguile -- high level interface} and @ref{Libguile -- +SCM interface} showed how to make C libraries available from Scheme. +Here I will describe some automated tools that the Guile team has made +available. Some have been written especially for Guile (the Guile Magic +Snarfer), and some are also in use with other languages (Python, Perl, +...) + +@menu +* By hand with gh_:: +* By hand with Guile Magic Snarfer:: +* Automatically using libtool:: +* Automatically using SWIG:: +@end menu + +@node By hand with gh_ +@section By hand with gh_ + +@node By hand with Guile Magic Snarfer +@section By hand with Guile Magic Snarfer + +When writing C code for use with Guile, you typically define a set of C +functions, and then make some of them visible to the Scheme world by +calling the @code{scm_make_gsubr} function; a C functions published in +this way is called a @dfn{subr}. If you have many subrs to publish, it +can sometimes be annoying to keep the list of calls to +@code{scm_make_gsubr} in sync with the list of function definitions. +Frequently, a programmer will define a new subr in C, recompile his +application, and then discover that the Scheme interpreter cannot see +the subr, because he forgot to call @code{scm_make_gsubr}. + +Guile provides the @code{guile-snarf} command to manage this problem. +Using this tool, you can keep all the information needed to define the +subr alongside the function definition itself; @code{guile-snarf} will +extract this information from your source code, and automatically +generate a file of calls to @code{scm_make_gsubr} which you can +@code{#include} into an initialization function. (The command name +comes from the verb ``to snarf'', here meaning ``to unceremoniously +extract information from a somewhat unwilling source.'') + +@menu +* How guile-snarf works:: Using the @code{guile-snarf} command. +* Macros guile-snarf recognizes:: How to mark up code for @code{guile-snarf}. +@end menu + +@node How guile-snarf works +@subsection How @code{guile-snarf} works + +For example, here is how you might define a new subr called +@code{clear-image}, implemented by the C function @code{clear_image}: + +@example +@group +#include <libguile.h> + +@dots{} + +SCM_PROC (s_clear_image, "clear-image", 1, 0, 0, clear_image); + +SCM +clear_image (SCM image_smob) +@{ + @dots{} +@} + +@dots{} + +void +init_image_type () +@{ +#include "image-type.x" +@} +@end group +@end example + +The @code{SCM_PROC} declaration says that the C function +@code{clear_image} implements a Scheme subr called @code{clear-image}, +which takes one required argument, no optional arguments, and no tail +argument. @code{SCM_PROC} also declares a static array of characters +named @code{s_clear_image}, initialized to the string +@code{"clear-image"}. The body of @code{clear_image} may use the array +in error messages, instead of writing out the literal string; this may +save string space on some systems. + +Assuming the text above lives in a file named @file{image-type.c}, you will +need to execute the following command to compile this file: +@example +guile-snarf image-type.c > image-type.x +@end example +@noindent This scans @file{image-type.c} for @code{SCM_PROC} +declarations, and sends the following output to the file +@file{image-type.x}: +@example +scm_make_gsubr (s_clear_image, 1, 0, 0, clear_image); +@end example +When compiled normally, @code{SCM_PROC} is a macro which expands to a +declaration of the @code{s_clear_image} string. + +In other words, @code{guile-snarf} scans source code looking for uses of +the @code{SCM_PROC} macro, and generates C code to define the +appropriate subrs. You need to provide all the same information you +would if you were using @code{scm_make_gsubr} yourself, but you can +place the information near the function definition itself, so it is less +likely to become incorrect or out-of-date. + +If you have many files that @code{guile-snarf} must process, you should +consider using a rule like the following in your Makefile: +@example +.SUFFIXES: .x +.c.x: + ./guile-snarf $(DEFS) $(INCLUDES) $(CPPFLAGS) $(CFLAGS) $< > $@ +@end example +This tells make to run @code{guile-snarf} to produce each needed +@file{.x} file from the corresponding @file{.c} file. + +@code{guile-snarf} passes all its command-line arguments directly to the +C preprocessor, which it uses to extract the information it needs from +the source code. this means you can pass normal compilation flags to +@code{guile-snarf} to define preprocessor symbols, add header file +directories, and so on. + + + +@node Macros guile-snarf recognizes +@subsection Macros @code{guile-snarf} recognizes + +Here are the macros you can use in your source code from which +@code{guile-snarf} can construct initialization code: + + +@defmac SCM_PROC (@var{namestr}, @var{name}, @var{req}, @var{opt}, @var{tail}, @var{c_func}) +Declare a new Scheme primitive function, or @dfn{subr}. The new subr +will be named @var{name} in Scheme code, and be implemented by the C +function @var{c_func}. The subr will take @var{req} required arguments +and @var{opt} optional arguments. If @var{tail} is non-zero, the +function will accept any remaining arguments as a list. + +Use this macro outside all function bodies, preferably above the +definition of @var{c_func} itself. When compiled, the @code{SCM_PROC} +declaration will expand to a definition for the @var{namestr} array, +initialized to @var{name}. The @code{guile-snarf} command uses this +declaration to automatically generate initialization code to create the +subr and bind it in the top-level environment. @xref{How guile-snarf +works}, for more info. + +@xref{Subrs}, for details on argument passing and how to write +@var{c_func}. +@end defmac + + +@defmac SCM_GLOBAL (@var{var}, @var{scheme_name}) +Declare a global Scheme variable named @var{scheme_name}, and a static C +variable named @var{var} to point to it. The value of the Scheme +variable lives in the @sc{cdr} of the cell @var{var} points to. +Initialize the variable to @code{#f}. + +Use this macro outside all function bodies. When compiled, the +@code{SCM_GLOBAL} macro will expand to a definition for the variable +@var{var}, initialized to an innocuous value. The @code{guile-snarf} +command will use this declaration to automatically generate code to +create a global variable named @var{scheme_name}, and store a pointer to +its cell in @var{var}. +@end defmac + + +@defmac SCM_CONST_LONG (@var{var}, @var{scheme_name}, @var{value}) +Like @code{SCM_GLOBAL}, but initialize the variable to @var{value}, +which must be an integer. +@end defmac + + +@defmac SCM_SYMBOL (@var{var}, @var{name}) +Declare a C variable of type @code{SCM} named @var{var}, and initialize +it to the Scheme symbol object whose name is @var{name}. + +Use this macro outside all function bodies. When compiled, the +@code{SCM_SYMBOL} macro will expand to a definition for the variable +@var{var}, initialized to an innocuous value. The @code{guile-snarf} +command will use this declaration to automatically generate code to +create a symbol named @var{name}, and store it in @var{var}. +@end defmac + +@node Automatically using libtool +@section Automatically using libtool + +@node Automatically using SWIG +@section Automatically using SWIG |