Since GCC 4.4 applying the malloc attribute to realloc-like
functions does not work under the documented constraints because
the contents of the memory pointed to are not properly transfered
from the realloc argument (or treated as pointing to anything,
like 4.3 behaved).
The following adjusts documentation to reflect implementation
reality (we do have an implementation detail that treats the
memory blob returned for non-builtins as pointing to any global
variable, but that is neither documented nor do I plan to do
so - I presume it is to allow allocation + initialization
routines to be marked with malloc, but even that area looks
susceptible to misinterpretation to me).
Any comments?
Thanks,
Richard.
2012-01-09 Richard Guenther <rguent...@suse.de>
* doc/extend.texi (malloc attribute): Adjust according to
implementation.
Index: gcc/doc/extend.texi
===================================================================
--- gcc/doc/extend.texi (revision 183001)
+++ gcc/doc/extend.texi (working copy)
@@ -2771,13 +2771,12 @@ efficient @code{jal} instruction.
@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.
+alias any other pointer valid when the function returns and that the memory
+has undefined content.
This will often improve optimization.
Standard functions with this property include @code{malloc} and
-@code{calloc}. @code{realloc}-like functions have this property as
-long as the old pointer is never referred to (including comparing it
-to the new pointer) after the function returns a non-@code{NULL}
-value.
+@code{calloc}. @code{realloc}-like functions do not have this
+property as the memory pointed to does not have undefined content.
@item mips16/nomips16
@cindex @code{mips16} attribute
