https://gcc.gnu.org/bugzilla/show_bug.cgi?id=106416
Bug ID: 106416
Summary: -Wint-conversion should be an error, not a pedwarn
Product: gcc
Version: 13.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c
Assignee: unassigned at gcc dot gnu.org
Reporter: redi at gcc dot gnu.org
Target Milestone: ---
Aaron Ballman and I discussed this recently, and now he just made this an error
in Clang, with the following justification:
Clang has traditionally allowed C programs to implicitly convert
integers to pointers and pointers to integers, despite it not being
valid to do so except under special circumstances (like converting the
integer 0, which is the null pointer constant, to a pointer). In C89,
this would result in undefined behavior per 3.3.4, and in C99 this rule
was strengthened to be a constraint violation instead. Constraint
violations are most often handled as an error.
This patch changes the warning to default to an error in all C modes
(it is already an error in C++). This gives us better security posture
by calling out potential programmer mistakes in code but still allows
users who need this behavior to use -Wno-error=int-conversion to retain
the warning behavior, or -Wno-int-conversion to silence the diagnostic
entirely.
GCC should do the same, for the same reasons. It's an error, and should not be
accepted by default in 2022.
I tried to look at how to change gcc/c/c-typeck.cc so that the pedwarns in
convert_for_assignment are errors by default, unless you use
-Wno-error=int-conversion, but I'm not sure how to make that happen.
