Microsoft and other non-GNU compilers don't recognize gcc tricks
like /*NOTREACHED*/ to suppress individual warnings. clang recognizes most
of them because it tries to be gcc-compatible. Because of that, a lot of
potentially useful warnings have had to be completely suppressed in the
past in all source files when using the non-gcc compatible compilers.
Now that the code is C99, take advantage of a way to suppress warnings for
individual functions, a big step up from suppressing the warnings
altogether.
Unfortunately, it does require a bit of ugliness caused by the
insertion of some macros in a few spots, but I'm not aware of
a cleaner alternative that still allows warnings to be enabled
in general, while suppressing a warning for known white-listed
instances.
Prior to the warning-tiggering function, place whichever one of
the following is needed to suppress the warning being encountered:
DISABLE_WARNING_UNREACHABLE_CODE
DISABLE_WARNING_CONDEXPR_IS_CONSTANT
After the warning-triggering function, place this:
RESTORE_WARNINGS
Under the hood, the compiler-appropriate warning-disabling
mechanics involve the use of C99 _Pragma, which can be used
in macros.
For unrecognized or inappropriate compilers, or if
DISABLE_WARNING_PRAGMAS is defined, the macros expand
to nothing.
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