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From: "amonakov at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug preprocessor/112701] New: wrong type inference for ternary
 operator in preprocessing context
Date: Fri, 24 Nov 2023 14:56:57 +0000
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X-Bugzilla-Type: new
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X-Bugzilla-Product: gcc
X-Bugzilla-Component: preprocessor
X-Bugzilla-Version: 13.0
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X-Bugzilla-Who: amonakov at gcc dot gnu.org
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D112701

            Bug ID: 112701
           Summary: wrong type inference for ternary operator in
                    preprocessing context
           Product: gcc
           Version: 13.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: preprocessor
          Assignee: unassigned at gcc dot gnu.org
          Reporter: amonakov at gcc dot gnu.org
  Target Milestone: ---

In the following snippet, the result of the ternary operator is (-1, cast t=
o an
unsigned type), so the comparison yields false, and both conditional inclus=
ions
must come out empty:

#if (0 ? 0u : -1) < 0
int foo =3D (0 ? 0u : -1) < 0;
#endif

#if (0 ? 0/0u : -1) < 0
int bar =3D (0 ? 0/0u : -1) < 0;
#endif

However, GCC emits:

bar:
        .zero   4

So clearly the evaluation of the second expression is inconsistent between
preprocessing context (where it incorrectly yields 1) vs. initializer conte=
xt
(where it is zero as it should be, as seen from the resulting asm).=