[cfe-dev] __attribute__((alloc_size(foo))

Jordan Rose jediknil at belkadan.com
Wed May 23 12:29:10 PDT 2012

Xi Wang took a stab at this back in February but no one finished reviewing his patch.[1][2] I'll take a look at yours soon, but maybe Xi has an opinion as well?


P.S. If we want to go really crazy, alloc_foo_objects(int howmany) could be handled with an extension to alloc_size: __attribute__((alloc_size(1,sizeof(struct foo)))). But that can wait for later.

[1]: http://lists.cs.uiuc.edu/pipermail/cfe-commits/Week-of-Mon-20120227/054264.html
[2]: http://lists.cs.uiuc.edu/pipermail/cfe-dev/2012-February/019952.html

On May 23, 2012, at 13:54, Nuno Lopes wrote:

> Hi,
> Please find in attach a patch that implements the attribute alloc_size. This attribute was introduced with GCC 4.3.
> Intended usage:
> void* my_malloc(size_t) __attribute__((alloc_size(1)));
> void* my_calloc(size_t, size_t) __attribute__((alloc_size(1,2)));
> void* my_realloc(void*, size_t) __attribute__((alloc_size(2)));
> The attribute basically declares that a function returns memory of size given by the product of the parameters listed in the attribute.
> More info: http://gcc.gnu.org/onlinedocs/gcc/Function-Attributes.html
> This patch only adds Sema support for the attribute. Wiring for codegen and static analyzer will come later.
> Any comments, suggestions, etc?
> Thanks,
> Nuno
> P.S.: This attribute is not expressive enough for functions that e.g. return x elements, like 'alloc_foo_objects(int howmany)'. However, since gcc already has this attribute and software out there is already using it, I think we should support it, even if we come up with a better attribute later.
> <alloc_size_attr.txt>_______________________________________________
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