RFC: __attribute_alloc_size__ on allocation functions (BZ#23741)

[Paul Eggert]

On 11/9/18 7:11 AM, Adhemerval Zanella wrote:
> It seems that some*very*  specific programs do allocate objects larger PTRDIFF_MAX,

On the other hand, GNU coreutils, GNU Emacs and several other programs 
do just the opposite: they uses wrappers around malloc that fail without 
calling malloc if the requested size exceeds PTRDIFF_MAX. This is to 
avoid the compiler gotchas mentioned in this thread.

For almost all applications malloc and friends should never allocate 
such objects as they cause more problems than they cure. The very few 
applications that need and can safely use objects larger than 
PTRDIFF_MAX can use mmap. And for mmap, I wouldn't mind if glibc mmap 
added a flag MMAP_EXCEED_PTRDIFF, so that mmap could reject requests for 
sizes greater than PTRDIFF_MAX unless this new flag is used.