Feature request: implement gcc's attribute access

[fefe17]

It's the first attribute in their documentation: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html

Here's how it works on gcc:

__attribute__ ((access (read_only, 1)))
int puts (const char*);

__attribute__ ((access (read_only, 2, 3)))
void* memcpy (void*, const void*, size_t);

This strengthens the ability of clang to give good warnings during compilation. It would also make clang-tidy stronger.

[llvmbot]

@llvm/issue-subscribers-clang-frontend

Author: None (fefe17)

It's the first attribute in their documentation:

https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html

Here's how it works on gcc:

attribute ((access (read_only, 1)))
int puts (const char*);

attribute ((access (read_only, 2, 3)))
void* memcpy (void*, const void*, size_t);

This strengthens the ability of clang to give good warnings during compilation.
It would also make clang-tidy stronger.

attribute malloc has these forms on gcc:

malloc
malloc (deallocator)
malloc (deallocator, ptr-index)

clang only supports the first one apparently. This is useful for situations like opendir (free using closedir not free!)

[thesamesam]

malloc is already covered by #53152.