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| author | Cassio Neri <cassio.neri@gmail.com> | 2023-11-12 01:33:52 +0000 |
|---|---|---|
| committer | Jonathan Wakely <jwakely@redhat.com> | 2023-11-14 22:32:08 +0000 |
| commit | f6ce081d0ffb5f25d71eb2f30fcfdff7f20dba22 (patch) | |
| tree | beb9a50210c8d8edcae4a919c9dc678cfac1cc23 /libcpp | |
| parent | 86a0df1a6c7fe4a835620b868e76ea78d42d6620 (diff) | |
| download | gcc-f6ce081d0ffb5f25d71eb2f30fcfdff7f20dba22.zip gcc-f6ce081d0ffb5f25d71eb2f30fcfdff7f20dba22.tar.gz gcc-f6ce081d0ffb5f25d71eb2f30fcfdff7f20dba22.tar.bz2 | |
libstdc++: Fix UB in weekday::weekday(sys_days) and add test
The following has undefined behaviour (signed overflow) [1]:
weekday max{sys_days{days{numeric_limits<days::rep>::max()}}};
The issue is in this line when __n is very large and __n + 4 overflows:
return weekday(__n >= -4 ? (__n + 4) % 7 : (__n + 5) % 7 + 6);
In addition to fixing this bug, the new implementation makes the compiler emit
shorter and branchless code for x86-64 and ARM [2].
[1] https://godbolt.org/z/1s5bv7KfT
[2] https://godbolt.org/z/zKsabzrhs
libstdc++-v3/ChangeLog:
* include/std/chrono (weekday::_S_from_days): Fix UB.
* testsuite/std/time/weekday/1.cc: Add test for overflow.
Diffstat (limited to 'libcpp')
0 files changed, 0 insertions, 0 deletions