X-Git-Url: http://review.tizen.org/git/?a=blobdiff_plain;f=glib%2Fgalloca.h;h=483a6c805acfe9045a7b9b540bf82c2150fd3a86;hb=14f2376c8a06f0936d734ec6a7e0e836072acf65;hp=34c75e61f28e78e74d48721800a7aca78b4c9875;hpb=f4bb21aa1d405fd11043a03e0962358eb0f42a5e;p=platform%2Fupstream%2Fglib.git

diff --git a/glib/galloca.h b/glib/galloca.h
index 34c75e6..483a6c8 100644
--- a/glib/galloca.h
+++ b/glib/galloca.h
@@ -12,9 +12,7 @@
  * 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, write to the
- * Free Software Foundation, Inc., 59 Temple Place - Suite 330,
- * Boston, MA 02111-1307, USA.
+ * License along with this library; if not, see <http://www.gnu.org/licenses/>.
  */
 
 /*
@@ -24,16 +22,18 @@
  * GLib at ftp://ftp.gtk.org/pub/gtk/.
  */
 
-#if defined(G_DISABLE_SINGLE_INCLUDES) && !defined (__G_LIB_H__) && !defined (GLIB_COMPILATION)
-#error "Only <glib.h> can be included directly."
-#endif
-
 #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>
 
-#ifdef  __GNUC__
+#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)
@@ -57,7 +57,47 @@ G_END_DECLS
 # 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__ */