Hi, On Thu, 13 Dec 2018 at 19:14, Jeff Law <l...@redhat.com> wrote: > > 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.
This new test fails on arm (and other 32 bits targets according to gcc-testresults) FAIL: gcc.dg/tree-ssa/builtin-snprintf-4.c (test for warnings, line 106) FAIL: gcc.dg/tree-ssa/builtin-snprintf-4.c (test for warnings, line 128) FAIL: gcc.dg/tree-ssa/builtin-snprintf-4.c (test for warnings, line 74) FAIL: gcc.dg/tree-ssa/builtin-snprintf-4.c (test for warnings, line 87) FAIL: gcc.dg/tree-ssa/builtin-snprintf-4.c scan-tree-dump-times optimized " = snprintf" 12 FAIL: gcc.dg/tree-ssa/builtin-snprintf-4.c scan-tree-dump-times optimized " = vsnprintf" 12 Christophe > OK > jeff
