cpython/Mac/Tools/pythonw.c

/*
 * This wrapper program executes a python executable hidden inside an
 * application bundle inside the Python framework. This is needed to run
 * GUI code: some GUI API's don't work unless the program is inside an
 * application bundle.
 *
 * This program uses posix_spawn rather than plain execv because we need
 * slightly more control over how the "real" interpreter is executed.
 */
#include <unistd.h>
#include <spawn.h>
#include <stdio.h>
#include <string.h>
#include <errno.h>
#include <err.h>
#include <dlfcn.h>
#include <stdlib.h>
#include <Python.h>


extern char** environ;

/*
 * Locate the python framework by looking for the
 * library that contains Py_Initialize.
 *
 * In a regular framework the structure is:
 *
 *    Python.framework/Versions/2.7
 *    		/Python
 *		/Resources/Python.app/Contents/MacOS/Python
 *
 * In a virtualenv style structure the expected
 * structure is:
 *
 *    ROOT
 *       /bin/pythonw
 *       /.Python   <- the dylib
 *       /.Resources/Python.app/Contents/MacOS/Python
 *
 * NOTE: virtualenv's are not an officially supported 
 * feature, support for that structure is provided as
 * a convenience.
 */
static char* get_python_path(void)
{
	size_t len;
	Dl_info info;
	char* end;
	char* g_path;

	if (dladdr(Py_Initialize, &info) == 0) {
		return NULL;
	}

	len = strlen(info.dli_fname);

	g_path = malloc(len+60);
	if (g_path == NULL) {
		return NULL;
	}

	strcpy(g_path, info.dli_fname);
	end = g_path + len - 1;
	while (end != g_path && *end != '/') {
		end --;
	}
	end++;
	if (end[1] == '.') {
		end++;
	}
	strcpy(end, "Resources/Python.app/Contents/MacOS/Python");

	return g_path;
}

static void
setup_spawnattr(posix_spawnattr_t* spawnattr)
{
	size_t ocount;
	size_t count;
	cpu_type_t cpu_types[1];
	short flags = 0;
#ifdef __LP64__
	int   ch;
#endif

	if ((errno = posix_spawnattr_init(spawnattr)) != 0) {
		err(2, "posix_spawnattr_int");
		/* NOTREACHTED */
	}

	count = 1;

	/* Run the real python executable using the same architure as this 
	 * executable, this allows users to controle the architecture using 
	 * "arch -ppc python"
	 */

#if defined(__ppc64__)
	cpu_types[0] = CPU_TYPE_POWERPC64;

#elif defined(__x86_64__)
	cpu_types[0] = CPU_TYPE_X86_64;

#elif defined(__ppc__)
	cpu_types[0] = CPU_TYPE_POWERPC;
#elif defined(__i386__)
	cpu_types[0] = CPU_TYPE_X86;
#else
#	error "Unknown CPU"
#endif

	if (posix_spawnattr_setbinpref_np(spawnattr, count, 
				cpu_types, &ocount) == -1) {
		err(1, "posix_spawnattr_setbinpref");
		/* NOTREACHTED */
	}
	if (count != ocount) {
		fprintf(stderr, "posix_spawnattr_setbinpref failed to copy\n");
		exit(1);
		/* NOTREACHTED */
	}


	/* 
	 * Set flag that causes posix_spawn to behave like execv
	 */
	flags |= POSIX_SPAWN_SETEXEC;
	if ((errno = posix_spawnattr_setflags(spawnattr, flags)) != 0) {
		err(1, "posix_spawnattr_setflags");
		/* NOTREACHTED */
	}
}

int 
main(int argc, char **argv) {
	posix_spawnattr_t spawnattr = NULL;
	char* exec_path = get_python_path();


	setup_spawnattr(&spawnattr);		
	posix_spawn(NULL, exec_path, NULL,
		&spawnattr, argv, environ);
	err(1, "posix_spawn: %s", argv[0]);
	/* NOTREACHED */
}