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From: Jonathan Wakely <redi@gcc.gnu.org> To: gcc-cvs@gcc.gnu.org, libstdc++-cvs@gcc.gnu.org Subject: [gcc r13-4615] libstdc++: Add a test checking for chrono::duration overflows Date: Mon, 12 Dec 2022 14:01:11 +0000 (GMT) [thread overview] Message-ID: <20221212140111.50CEB385008B@sourceware.org> (raw) https://gcc.gnu.org/g:dc94eaab008165698a1161c757db96fc701103a2 commit r13-4615-gdc94eaab008165698a1161c757db96fc701103a2 Author: Jonathan Wakely <jwakely@redhat.com> Date: Mon Dec 12 12:51:49 2022 +0000 libstdc++: Add a test checking for chrono::duration overflows This test fails if chrono::days::rep or chrono::years::rep is a 32-bit type, because a large days or years value silently overflows a 32-bit integer when converted to seconds. It would be conforming to implement chrono::days as chrono::duration<int32_t, ratio<86400>>, but would make this overflow case more likely. Similarly for chrono::years, chrono::months and chrono::weeks. This test is here to remind us not to make that change lightly. libstdc++-v3/ChangeLog: * testsuite/20_util/duration/arithmetic/overflow_c++20.cc: New test. Diff: --- .../20_util/duration/arithmetic/overflow_c++20.cc | 29 ++++++++++++++++++++++ 1 file changed, 29 insertions(+) diff --git a/libstdc++-v3/testsuite/20_util/duration/arithmetic/overflow_c++20.cc b/libstdc++-v3/testsuite/20_util/duration/arithmetic/overflow_c++20.cc new file mode 100644 index 00000000000..42fa7ea55fb --- /dev/null +++ b/libstdc++-v3/testsuite/20_util/duration/arithmetic/overflow_c++20.cc @@ -0,0 +1,29 @@ +// { dg-options "-std=gnu++20" } +// { dg-do run { target c++20 } } + +#include <chrono> +#include <cstdint> +#include <testsuite_hooks.h> + +void +test_overflow() +{ + using namespace std::chrono; + + using seconds32_t = duration<std::int_least32_t>; + seconds32_t t = 14h + 25min + 55s; + auto snow = sys_days(1854y/December/11); + auto snow_t = snow + t; + // Fails if days::rep is 32-bit: + VERIFY( snow_t.time_since_epoch() < seconds::zero() ); + auto y = floor<years>(snow); + auto y_t = y + t; + // Fails if years::rep is 32-bit: + VERIFY( y_t.time_since_epoch() < seconds::zero() ); + VERIFY( y_t < snow_t ); +} + +int main() +{ + test_overflow(); +}
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