On 12/12/18 4:18 PM, Martin Sebor wrote:
> POSIX requires snprintf to fail with EOVERFLOW when the specified
> bound exceeds INT_MAX. This requirement conflicts with the C
> requirements on valid calls to the function and isn't universally
> implemented (e.g., Glibc doesn't seem to follow it, and GCC has
> historically not paid heed to it either). Nevertheless, there
> are implementations that do respect it (Solaris being one of
> them), and it seems that GCC should make a tricky situation
> even more treacherous for programmers by returning different
> values from some calls to the function than the library would.
> This is also what bug 87096 requests. The patch also adds
> a warning that was missing from a subset of these troublesome
> calls.
>
> The attached patch disables the snprintf constant folding and
> range optimization for calls to it and other related bounded
> functions when the bound is not known not to exceed INT_MAX.
>
> Tested on x86_64-linux.
>
> Martin
>
> gcc-87096.diff
>
> PR tree-optimization/87096 - Optimised snprintf is not POSIX conformant
>
> gcc/ChangeLog:
>
> PR rtl-optimization/87096
> * gimple-ssa-sprintf.c (sprintf_dom_walker::handle_gimple_call): Avoid
> folding calls whose bound may exceed INT_MAX. Diagnose bound ranges
> that exceed the limit.
>
> gcc/testsuite/ChangeLog:
>
> PR tree-optimization/87096
> * gcc.dg/tree-ssa/builtin-snprintf-4.c: New test.
OK
jeff
