Clang should warn on the use of reserved identifier/macro names

[rubenvb]

Bugzilla Link	11488
Resolution	FIXED
Resolved on	Aug 18, 2021 09:50
Version	trunk
OS	All
CC	@davidstone,@gnzlbg,@miyuki,@seanm,@spavloff

Extended Description

For C, Clang should warn when user code uses identifiers or macros that are implementation-reserved.

For C(99), this would mean names starting with an underscore followed by another unerscore or capitalized letter.

For C++ a single underscore is also reserved for the global namespace.

I could have messed the above rules up, but these are the cause of a lot of unexpected bugs, and a warning would be super-easy to implement.

[llvmbot]

Also, Clang should warn when someone #defines override or final:

[macro.names] states: "A translation unit shall not #define or #undef names lexically identical to keywords, to the identifiers listed in Table 3, or to the attribute-tokens described in 7.6."

"Table 3 — Identifiers with special meaning
override final"

[dwblaikie]

*** Bug llvm/llvm-bugzilla-archive#21284 has been marked as a duplicate of this bug. ***

[spavloff]

Partially fixed by r224012, r224100 and r224512.

[davidstone]

-Wreserved-identifier seems to cover this.

[dwblaikie]

mentioned in issue llvm/llvm-bugzilla-archive#21284