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From: "pinskia at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
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Subject: [Bug libstdc++/89979] subtract_with_carry_engine incorrect carry flag
Date: Sun, 22 Aug 2021 21:46:46 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D89979

--- Comment #3 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
LLVM's libc++ does not go into the 0 loop but still does not do a good job:
4294967295 0 0 0 0 0 0 1
0 0 0 0 0 0 0 1
0 0 0 0 0 0 4294967295 1
0 0 0 0 0 4294967295 4294967295 1
0 0 0 0 4294967295 4294967295 4294967295 1
0 0 0 4294967295 4294967295 4294967295 4294967294 0
0 0 4294967295 4294967295 4294967295 4294967294 4294967295 0
0 4294967295 4294967295 4294967295 4294967294 4294967295 4294967295 0
4294967295 4294967295 4294967295 4294967294 4294967295 4294967295 429496729=
4 0
4294967295 4294967295 4294967294 4294967295 4294967295 4294967294 0 0
4294967295 4294967294 4294967295 4294967295 4294967294 0 0 0
4294967294 4294967295 4294967295 4294967294 0 0 4294967295 1


While libstdc++ does seems to get into a loop:
4294967295 0 0 0 0 0 0 1 0
0 0 0 0 0 0 0 0 1
0 0 0 0 0 0 0 0 2
0 0 0 0 0 0 0 0 3
0 0 0 0 0 0 0 0 4
0 0 0 0 0 0 0 0 5
0 0 0 0 0 0 0 0 6
0 0 0 0 0 0 0 0 0
0 0 0 0 0 0 0 0 1
0 0 0 0 0 0 0 0 2
0 0 0 0 0 0 0 0 3
0 0 0 0 0 0 0 0 4=