[Bug middle-end/79929] [7 Regression] Bogus Warning: '__builtin_memset': specified size 4294967291 exceeds maximum object size 2147483647

[msebor at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=79929

--- Comment #9 from Martin Sebor <msebor at gcc dot gnu.org> ---
I actually think that for the test case in comment #4, the warning does
highlight a problem in the code: since the test (p < c) can never be true the
memset can never be called in a valid program.  At -O2 the problem is detected
by -Wstrict-overflow.  Unfortunately, because -Wstrict-overflow is only issued
when an optimization takes place that depends on the absence of an overflow, it
can't be issued at -O1 when the condition isn't removed.  I still think that
eliminating the memset call (or replacing it with a trap) when the size is
known to be excessive is a viable strategy.  (For memset perhaps under an
option to allow for the rare programs that make use of Physical Address
Extension and clear memory regions larger than 2GB.)