12 A toy library interface to GCC

The library (vicare gcc) is installed along with Vicare; it implements a toy interface to gcc, the GNU C Compiler. Its purpose is to build, at runtime, a C language shared library from possibly dynamically constructed C code; then load the library and access a C function as FFI callout.

(vicare gcc) must be considered as a toy to demonstrate the features of Vicare; it is installed only if the POSIX, GNU C library and Libffi APIs are enabled at package configuration time.

The following is an example of function to increment an integer:

#!r6rs
(import (vicare)
  (prefix (vicare gcc) gcc.))

(gcc.initialise "/usr/local/bin/gcc" "/home/marco/var/tmp/")

(gcc.define-c-function
  signed-int incr (signed-int)
  "#include <stdio.h>
   int incr (int a) {
     return 1+a;
   }")

(incr 1)        ⇒ 2

the code creates a shared library libincr.so in a subdirectory of the given initialisation directory, then load it and access the symbol incr.

(vicare gcc) depends upon the following libraries:

(vicare ffi)
(vicare posix)
(vicare glibc)
(vicare platform constants)
(vicare language-extensions syntaxes)

Function: initialise gcc tmpdir

Initialise the library. gcc must be the string full filename of the GCC executable. tmpdir must be the string pathname of an existing directory on a partition with executable permissions; it is used to create temporary files, including the shared libraries.

Temporary files go in a subdirectory of tmpdir; it is the responsibility of the system administrator to clean up regularly such subdirectories.

Syntax: define-c-function ?retval ?name ?args ?code

Define a new Scheme function wrapping a C function from a shared library. ?name must be an identifier representing the name of the function.

?retval must be a symbol selecting the type of the return value; ?args must be a list of symbols selecting the types of the arguments; (vicare-scheme)Specifying native types for details.

?code must be a Scheme string representing the C code to be compiled.

Parameter: COMPILE-FLAGS

References a list of string. Base options for the compiler, it is initialised to ("-c").

Parameter: LINK-FLAGS

References a list of string. Base options for the linker, it is initialised to ("-pipe" "-shared" "-fPIC").

Parameter: CFLAGS

References a list of string. Additional options for the compiler, it is initialised to ("-O2").

Parameter: LDFLAGS

References a list of string. Additional options for the linker, it is initialised to nil.