On Mon, Jan 16, 2017 at 05:06:40PM -0700, Martin Sebor wrote:
> The test case submitted in bug 79095 - [7 regression] spurious
> stringop-overflow warning shows that GCC optimizes some loops
> into calls to memset with size arguments in excess of the object
> size limit. Since such calls will unavoidably lead to a buffer
> overflow and memory corruption the attached patch detects them
> and replaces them with a trap. That both prevents the buffer
> overflow and eliminates the warning.
I fear this is going to break various 32-bit database programs and similar
that mmap say 3GB of RAM and then work on that memory chunk as contiguous.
Some things don't work too well in that case (pointer differences), but it
is unlikely they would be using those, while your patch actively breaks it
even for loops that can be transformed into memset (memcpy of course isn't a
problem, because you need some virtual address space to copy it from).
And as written in the PR, IMNSHO the warning should not be enabled by
default at its current verboseness and false positive rate.
Jakub
