[Bug c/67999] Wrong optimization of pointer comparisons

[bugdal at aerifal dot cx]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=67999

Rich Felker <bugdal at aerifal dot cx> changed:

           What    |Removed                     |Added
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                 CC|                            |bugdal at aerifal dot cx

--- Comment #6 from Rich Felker <bugdal at aerifal dot cx> ---
IMO there's nothing wrong with what GCC's doing, but library implementations
that allow allocations > PTRDIFF_MAX are buggy. musl has always gotten this
right and Bionic has fixed it recently; see
https://android-review.googlesource.com/#/c/170800/

Somebody should probably file a bug with glibc if there's not one already, but
clearly they're aware of this issue (Alexander Cherepanov pointed this out to
me): https://sourceware.org/ml/libc-alpha/2011-12/msg00066.html

The key part is:

"I don't think there's anything that can sensibly be done in the compiler 
about this issue; I think the only way to avoid security problems there is 
for malloc and other allocation functions to refuse to allocate objects 
using half or more of the address space..."