This was approved for C++26 last week at the WG21 meeting in Kona.
libstdc++-v3/ChangeLog:
* include/Makefile.am: Add new header.
* include/Makefile.in: Regenerate.
* include/bits/version.def (saturation_arithmetic): Define.
* include/bits/version.h: Regenerate.
* include/std/numeric: Include new header.
* include/bits/sat_arith.h: New file.
* testsuite/26_numerics/saturation/add.cc: New test.
* testsuite/26_numerics/saturation/cast.cc: New test.
* testsuite/26_numerics/saturation/div.cc: New test.
* testsuite/26_numerics/saturation/mul.cc: New test.
* testsuite/26_numerics/saturation/sub.cc: New test.
* testsuite/26_numerics/saturation/version.cc: New test.
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