Import Upstream version 2.72.4

glib/galloca.h

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+/* 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>
+#include <string.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.
+ *
+ * - Allowing @size to be specified by an untrusted party would allow for them
+ *   to trigger a segmentation fault by specifying a large size, leading to a
+ *   denial of service vulnerability. @size must always be entirely under the
+ *   control of the program.
+ *
+ * - 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_alloca0:
+ * @size: number of bytes to allocate.
+ *
+ * Wraps g_alloca() and initializes allocated memory to zeroes.
+ * If @size is `0` it returns %NULL.
+ *
+ * Note that the @size argument will be evaluated multiple times.
+ *
+ * Returns: (nullable) (transfer full): space for @size bytes, allocated on the stack
+ *
+ * Since: 2.72
+ */
+#define g_alloca0(size)  ((size) == 0 ? NULL : memset (g_alloca (size), 0, (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.
+ * 
+ * As mentioned in the documentation for g_alloca(), @n_structs must always be
+ * entirely under the control of the program, or you may introduce a denial of
+ * service vulnerability. In addition, the multiplication of @struct_type by
+ * @n_structs is not checked, so an overflow may lead to a remote code execution
+ * vulnerability.
+ *
+ * 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)))
+
+/**
+ * g_newa0:
+ * @struct_type: the type of the elements to allocate.
+ * @n_structs: the number of elements to allocate.
+ *
+ * Wraps g_alloca0() in a more typesafe manner.
+ *
+ * Returns: (nullable) (transfer full): Pointer to stack space for @n_structs
+ *   chunks of type @struct_type
+ *
+ * Since: 2.72
+ */
+#define g_newa0(struct_type, n_structs)  ((struct_type*) g_alloca0 (sizeof (struct_type) * (gsize) (n_structs)))
+
+#endif /* __G_ALLOCA_H__ */