https://gcc.gnu.org/bugzilla/show_bug.cgi?id=82272
Bug ID: 82272
Summary: RFE: request a warning for (<nonbool> == <bool>) etc.
Product: gcc
Version: unknown
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c
Assignee: unassigned at gcc dot gnu.org
Reporter: hpa at zytor dot com
Target Milestone: ---
People not familiar with C, or who have read misguided style guides, sometimes
write code like:
if (cond == true) {
....
}
instead of
if (cond) {
....
}
which has the potential to be disastrous if "cond" is a numeric type which is
*not* a bool as these two statements are distinctly different.
As such, it would be a very good thing if a warning could be emitted in this
case.
C99 and C11 requires that <stdbool.h> define true and false as "the integer
constant 1" and "the integer constant 0", respectively, and that those
expressions are usable in the preprocessor. I don't *believe* that that means
that they have to expand to the *tokens* 1 and 0, however (and there is always
the possibility to do a GNU extension.)
What I'm suggesting is to do something like _True and _False as cpp-safe
equivalent to (_Bool)1 and (_Bool)0, and warn on comparison between a _Bool and
a non-_Bool.
