/* GLIB - Library of useful routines for C programming * Copyright (C) 1995-1997 Peter Mattis, Spencer Kimball and Josh MacDonald * * This library is free software; you can redistribute it and/or * modify it under the terms of the GNU Lesser General Public * License as published by the Free Software Foundation; either * version 2.1 of the License, or (at your option) any later version. * * This library is distributed in the hope that it will be useful, * but WITHOUT ANY WARRANTY; without even the implied warranty of * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU * Lesser General Public License for more details. * * You should have received a copy of the GNU Lesser General Public * License along with this library; if not, see <http://www.gnu.org/licenses/>. */ /* * Modified by the GLib Team and others 1997-2000. See the AUTHORS * file for a list of people on the GLib Team. See the ChangeLog * files for a list of changes. These files are distributed with * GLib at ftp://ftp.gtk.org/pub/gtk/. */ #ifndef __G_ALLOCA_H__ #define __G_ALLOCA_H__ #if !defined (__GLIB_H_INSIDE__) && !defined (GLIB_COMPILATION) #error "Only <glib.h> can be included directly." #endif #include <glib/gtypes.h> #if defined(__BIONIC__) && defined (GLIB_HAVE_ALLOCA_H) # include <alloca.h> #elif defined(__GNUC__) /* GCC does the right thing */ # undef alloca # define alloca(size) __builtin_alloca (size) #elif defined (GLIB_HAVE_ALLOCA_H) /* a native and working alloca.h is there */ # include <alloca.h> #else /* !__GNUC__ && !GLIB_HAVE_ALLOCA_H */ # if defined(_MSC_VER) || defined(__DMC__) # include <malloc.h> # define alloca _alloca # else /* !_MSC_VER && !__DMC__ */ # ifdef _AIX # pragma alloca # else /* !_AIX */ # ifndef alloca /* predefined by HP cc +Olibcalls */ G_BEGIN_DECLS char *alloca (); G_END_DECLS # endif /* !alloca */ # endif /* !_AIX */ # endif /* !_MSC_VER && !__DMC__ */ #endif /* !__GNUC__ && !GLIB_HAVE_ALLOCA_H */ /** * g_alloca: * @size: number of bytes to allocate. * * Allocates @size bytes on the stack; these bytes will be freed when the current * stack frame is cleaned up. This macro essentially just wraps the alloca() * function present on most UNIX variants. * Thus it provides the same advantages and pitfalls as alloca(): * * - alloca() is very fast, as on most systems it's implemented by just adjusting * the stack pointer register. * * - It doesn't cause any memory fragmentation, within its scope, separate alloca() * blocks just build up and are released together at function end. * * - Allocation sizes have to fit into the current stack frame. For instance in a * threaded environment on Linux, the per-thread stack size is limited to 2 Megabytes, * so be sparse with alloca() uses. * * - Allocation failure due to insufficient stack space is not indicated with a %NULL * return like e.g. with malloc(). Instead, most systems probably handle it the same * way as out of stack space situations from infinite function recursion, i.e. * with a segmentation fault. * * - Special care has to be taken when mixing alloca() with GNU C variable sized arrays. * Stack space allocated with alloca() in the same scope as a variable sized array * will be freed together with the variable sized array upon exit of that scope, and * not upon exit of the enclosing function scope. * * Returns: space for @size bytes, allocated on the stack */ #define g_alloca(size) alloca (size) /** * g_newa: * @struct_type: Type of memory chunks to be allocated * @n_structs: Number of chunks to be allocated * * Wraps g_alloca() in a more typesafe manner. * * Returns: Pointer to stack space for @n_structs chunks of type @struct_type */ #define g_newa(struct_type, n_structs) ((struct_type*) g_alloca (sizeof (struct_type) * (gsize) (n_structs))) #endif /* __G_ALLOCA_H__ */