[glib] Bug 608196 - Overflow-safe g_new family

[Ryan Lortie <ryanl src gnome org>]

commit a1b9743e1816c5269029e8ae2e21e8950c411f5c
Author: Ryan Lortie <desrt desrt ca>
Date:   Sat Mar 6 23:21:27 2010 -0500

    Bug 608196 - Overflow-safe g_new family
    
    Remove the macros for the g_malloc_n family -- calls directly to those
    functions now always go directly to those functions.
    
    Reimplement the macros for g_new and friends.
    
    Remove the branch that checked for calling g_new() with a constant
    n_structs == 1.  With the struct size always known this case will now be
    caught under the case that does the inline multiplication and the
    multiplication by 1 will be optimised away.

 glib/gmem.c |    8 -----
 glib/gmem.h |   83 +++++++++++++++++++++++++----------------------------------
 2 files changed, 35 insertions(+), 56 deletions(-)
---
diff --git a/glib/gmem.c b/glib/gmem.c
index 76cfad1..36e04dd 100644
--- a/glib/gmem.c
+++ b/glib/gmem.c
@@ -37,14 +37,6 @@
 #include "glib.h"
 #include "gthreadprivate.h"
 
-/* Undef the macros before including galias.h */
-#undef g_malloc_n
-#undef g_malloc0_n
-#undef g_realloc_n
-#undef g_try_malloc_n
-#undef g_try_malloc0_n
-#undef g_try_realloc_n
-
 #include "galias.h"
 
 #define MEM_PROFILE_TABLE_SIZE 4096
diff --git a/glib/gmem.h b/glib/gmem.h
index fc5d95d..78950d5 100644
--- a/glib/gmem.h
+++ b/glib/gmem.h
@@ -76,67 +76,54 @@ gpointer g_try_realloc_n  (gpointer	 mem,
 			   gsize	 n_block_bytes) G_GNUC_WARN_UNUSED_RESULT;
 
 
-/* avoid the overflow check if we can determine at compile-time that no
- * overflow happens. */
+/* Optimise: avoid the call to the (slower) _n function if we can
+ * determine at compile-time that no overflow happens.
+ */
 #if defined (__GNUC__) && (__GNUC__ >= 2) && defined (__OPTIMIZE__)
-#  define _G_MALLOC_N(n_blocks, n_block_bytes, func_1, func_n) \
-	(__extension__ ({					\
-	  gsize __a = (gsize) (n_blocks);			\
-	  gsize __b = (gsize) (n_block_bytes);			\
+#  define _G_NEW(struct_type, n_structs, func) \
+	(struct_type *) (__extension__ ({			\
+	  gsize __n = (gsize) (n_structs);			\
 	  gpointer __p;						\
-	  if (__builtin_constant_p (__a) && __a == 1)		\
-	    __p = func_1 (__b);					\
-	  else if (__builtin_constant_p (__b) && __b == 1)	\
-	    __p = func_1 (__a);					\
-	  else if (__builtin_constant_p (__a) &&		\
-		   __builtin_constant_p (__b) &&		\
-		   __a <= G_MAXSIZE / __b)			\
-	    __p = func_1 (__a * __b);				\
+	  if (sizeof (struct_type) == 1)			\
+	    __p = g_##func (__n);				\
+	  else if (__builtin_constant_p (__n) &&		\
+	           __n <= G_MAXSIZE / sizeof (struct_type))	\
+	    __p = g_##func (__n * sizeof (struct_type));	\
 	  else							\
-	    __p = func_n (__a, __b);				\
+	    __p = g_##func##_n (__n, sizeof (struct_type));	\
 	  __p;							\
 	}))
-#  define _G_REALLOC_N(mem, n_blocks, n_block_bytes, func_1, func_n) \
-	(__extension__ ({					\
-	  gsize __a = (gsize) (n_blocks);			\
-	  gsize __b = (gsize) (n_block_bytes);			\
+#  define _G_RENEW(struct_type, mem, n_structs, func) \
+	(struct_type *) (__extension__ ({			\
+	  gsize __n = (gsize) (n_structs);			\
 	  gpointer __p = (gpointer) (mem);			\
-	  if (__builtin_constant_p (__a) && __a == 1)		\
-	    __p = func_1 (__p, __b);				\
-	  else if (__builtin_constant_p (__b) && __b == 1)	\
-	    __p = func_1 (__p, __a);				\
-	  else if (__builtin_constant_p (__a) &&		\
-		   __builtin_constant_p (__b) &&		\
-		   __a <= G_MAXSIZE / __b)			\
-	    __p = func_1 (__p, __a * __b);			\
+	  if (sizeof (struct_type) == 1)			\
+	    __p = g_##func (__p, __n);				\
+	  else if (__builtin_constant_p (__n) &&		\
+	           __n <= G_MAXSIZE / sizeof (struct_type))	\
+	    __p = g_##func (__p, __n * sizeof (struct_type));	\
 	  else							\
-	    __p = func_n (__p, __a, __b);			\
+	    __p = g_##func##_n (__p, __n, sizeof (struct_type));\
 	  __p;							\
 	}))
 
-#  define g_malloc_n(n_blocks,n_block_bytes)		_G_MALLOC_N (n_blocks, n_block_bytes, g_malloc, g_malloc_n)
-#  define g_malloc0_n(n_blocks,n_block_bytes)		_G_MALLOC_N (n_blocks, n_block_bytes, g_malloc0, g_malloc0_n)
-#  define g_realloc_n(mem,n_blocks,n_block_bytes)	_G_REALLOC_N (mem, n_blocks, n_block_bytes, g_realloc, g_realloc_n)
-#  define g_try_malloc_n(n_blocks,n_block_bytes)	_G_MALLOC_N (n_blocks, n_block_bytes, g_try_malloc, g_try_malloc_n)
-#  define g_try_malloc0_n(n_blocks,n_block_bytes)	_G_MALLOC_N (n_blocks, n_block_bytes, g_try_malloc0, g_try_malloc0_n)
-#  define g_try_realloc_n(mem,n_blocks,n_block_bytes)	_G_REALLOC_N (mem, n_blocks, n_block_bytes, g_try_realloc, g_try_realloc_n)
-#endif
+#else
 
+/* Unoptimised version: always call the _n() function. */
 
-/* Convenience memory allocators
- */
+#define _G_NEW(struct_type, n_structs, func) \
+        ((struct_type *) g_##func##_n ((n_structs), sizeof (struct_type)))
+#define _G_RENEW(struct_type, mem, n_structs, func) \
+        ((struct_type *) g_##func##_n (mem, (n_structs), sizeof (struct_type)))
+
+#endif
 
-#define _G_NEW(struct_type, n_structs, _g_malloc_n)	\
-	((struct_type *) _g_malloc_n ((n_structs), sizeof (struct_type)))
-#define _G_RENEW(struct_type, mem, n_structs, _g_realloc_n)	\
-	((struct_type *) _g_realloc_n ((mem), (n_structs), sizeof (struct_type)))
-
-#define g_new(struct_type, n_structs)			_G_NEW (struct_type, n_structs, g_malloc_n)
-#define g_new0(struct_type, n_structs)			_G_NEW (struct_type, n_structs, g_malloc0_n)
-#define g_renew(struct_type, mem, n_structs)		_G_RENEW (struct_type, mem, n_structs, g_realloc_n)
-#define g_try_new(struct_type, n_structs)		_G_NEW (struct_type, n_structs, g_try_malloc_n)
-#define g_try_new0(struct_type, n_structs)		_G_NEW (struct_type, n_structs, g_try_malloc0_n)
-#define g_try_renew(struct_type, mem, n_structs)	_G_RENEW (struct_type, mem, n_structs, g_try_realloc_n)
+#define g_new(struct_type, n_structs)			_G_NEW (struct_type, n_structs, malloc)
+#define g_new0(struct_type, n_structs)			_G_NEW (struct_type, n_structs, malloc0)
+#define g_renew(struct_type, mem, n_structs)		_G_RENEW (struct_type, mem, n_structs, realloc)
+#define g_try_new(struct_type, n_structs)		_G_NEW (struct_type, n_structs, try_malloc)
+#define g_try_new0(struct_type, n_structs)		_G_NEW (struct_type, n_structs, try_malloc0)
+#define g_try_renew(struct_type, mem, n_structs)	_G_RENEW (struct_type, mem, n_structs, try_realloc)
 
 
 /* Memory allocation virtualization for debugging purposes