https://gcc.gnu.org/bugzilla/show_bug.cgi?id=111063
Bug ID: 111063
Summary: [UBSAN] Implement "-inf is outside the range of
representable values of type 'unsigned long'" to be on
par with Clang
Product: gcc
Version: 14.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: sanitizer
Assignee: unassigned at gcc dot gnu.org
Reporter: burnus at gcc dot gnu.org
CC: dodji at gcc dot gnu.org, dvyukov at gcc dot gnu.org,
jakub at gcc dot gnu.org, kcc at gcc dot gnu.org, marxin at
gcc dot gnu.org
Target Milestone: ---
Jonathan Wakely wrote in bug 110860 comment 10:
-----------<cut>-------------------------
GCC's ubsan doesn't seem to diagnose this rule:
"A prvalue of a floating-point type can be converted to a prvalue of an integer
type. The conversion truncates; that is, the fractional part is discarded. The
behavior is undefined if the truncated value cannot be represented in the
destination type."
There's no ubsan diagnostic for:
unsigned long i = -HUGE_VAL;
So it doesn't complain about adding log10(0) to a size_t.
-----------<cut>-------------------------
That diagnostic exists in Clang as reported by
Paul Dreik in bug 110860 comment 8:
-----------<cut>-------------------------
When 0 is passed, log10 returns -inf, which can not be converted to an integer.
I had a bit of problem to reproduce this with gcc, but it worked with clang.
The following program:
#include <cstdio>
#include <format>
#include <string_view>
int main(int argc, char* argv[]) {
[[maybe_unused]] auto x = std::format("{:.292f}", 0.f);
}
causes the following output when compiled with clang-16 using
-fsanitize=undefined -fno-sanitize-recover=all -g -O0:
/opt/compiler-explorer/gcc-snapshot/lib/gcc/x86_64-linux-gnu/14.0.0/../../../../include/c++/14.0.0/format:1496:15:
runtime error: -inf is outside the range of representable values of type
'unsigned long'
SUMMARY: UndefinedBehaviorSanitizer: undefined-behavior
/opt/compiler-explorer/gcc-snapshot/lib/gcc/x86_64-linux-gnu/14.0.0/../../../../include/c++/14.0.0/format:1496:15
in
Link to reproducer (expected to go stale quick, had to use clang trunk to get a
sufficiently new libstdc++): https://godbolt.org/z/8aGf7YGWs
