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[PATCH] __attribute__ ((malloc)) doc fix (PR other/56955)


Attached is a proposed documentation patch for __attribute__ ((malloc)), taken from:

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=56955#c9

Richard Biener suggested that I forward it to this list.
Index: gcc/ChangeLog
===================================================================
--- gcc/ChangeLog	(revision 210629)
+++ gcc/ChangeLog	(working copy)
@@ -1,3 +1,10 @@
+2014-05-20  Paul Eggert  <eggert@cs.ucla.edu>
+
+	PR other/56955
+	* doc/extend.texi (Function Attributes): Fix  __attribute__ ((malloc))
+	documentation; the old documentation didn't clearly state the
+	constraints on the contents of the pointed-to storage.
+
 2014-05-19  David Wohlferd <dw@LimeGreenSocks.com>
 
 	* doc/extend.texi: Create Label Attributes section,
Index: gcc/doc/extend.texi
===================================================================
--- gcc/doc/extend.texi	(revision 210629)
+++ gcc/doc/extend.texi	(working copy)
@@ -3207,15 +3207,20 @@
 
 @item malloc
 @cindex @code{malloc} attribute
-The @code{malloc} attribute is used to tell the compiler that a function
-may be treated as if any non-@code{NULL} pointer it returns cannot
-alias any other pointer valid when the function returns and that the memory
-has undefined content.
-This often improves optimization.
-Standard functions with this property include @code{malloc} and
-@code{calloc}.  @code{realloc}-like functions do not have this
-property as the memory pointed to does not have undefined content.
+This tells the compiler that a function is @code{malloc}-like, i.e.,
+that if the function returns a non-null pointer @var{P}, then @var{P}
+cannot alias any other pointer valid when the function returns, and
+moreover the contents of any storage addressed by @var{P} cannot
+contain a pointer that aliases any other pointer valid when the
+function returns.
 
+Using this attribute often improves optimization.  Functions like
+@code{malloc} and @code{calloc} have this property because they return
+a pointer to uninitialized or zeroed-out storage.  However, functions
+like @code{realloc} do not have this property, as they can return a
+pointer to storage containing pointers that alias already-valid
+pointers.
+
 @item mips16/nomips16
 @cindex @code{mips16} attribute
 @cindex @code{nomips16} attribute

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