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From: "j at lambda dot is" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug gcov-profile/115047] Inconsistent MC/DC reported by GCC and
 LLVM
Date: Mon, 13 May 2024 18:51:12 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D115047

--- Comment #1 from J=C3=B8rgen Kvalsvik <j at lambda dot is> ---
gcc is not wrong here - f(1, 0, 0) =3D false, while f(1, 0, 1) =3D true so =
clearly
c has an independent effect on the outcome here, and both its values has be=
en
observed.

I think clang measures unique-cause and not masking MC/DC which probably
explains the difference (at least clang's documentation [1] does not specify
which form it measures. Since more than one variable change between the two
test vectors I assume that would be it. I don't have clang 19 available rig=
ht
now, does f(0, 0, 1); f(0, 0, 0); cover c?

[1]
https://clang.llvm.org/docs/SourceBasedCodeCoverage.html#mc-dc-instrumentat=
ion=