http://gcc.gnu.org/bugzilla/show_bug.cgi?id=51437
--- Comment #10 from Ruben Van Boxem <vanboxem.ruben at gmail dot com> 2012-02-19 09:33:05 UTC --- (In reply to comment #9) > (In reply to comment #8) > > You really do want to flag both definition and usage. For instance, there's > > plenty of buggy software (especially GNU software like binutils) using > > __pid_t > > and similar when it should be using pid_t, etc. > > In the case of identifiers containing __ or starting with _[A-Z], that does > hold true; I hadn't considered programs using internal identifiers when > corresponding public identifiers exist. (Ideally the headers could have > avoided exposing those internal identifiers to user programs in the first > place, but I don't know any sensible way to implement that.) > > However, note that the standards also reserve various other classes of names, > such as types ending in _t, for which GCC should only flag definitions, not > uses. Only system headers should define new _t types, but user code can *use* > types like time_t or pid_t without warning. These are only reserved for POSIX, and should not always be warned about! > > (Some of the other reserved identifier categories, such as E[A-Z0-9].*, > is[a-z].*, to[a-z].*, and mem[a-z].* should go under some separate, more > pedantic warning option.) I don't see why this should happen at all. There's nothing special about these general names? > > > From an undefined behavior standpoint, defining a name in the reserved > > namespace is no worse than using a name in the referred namespace assuming > > the > > implementation has defined it. Both are incorrect C usage and both should be > > flagged. > > True. I had mostly wanted to avoid generating hundreds of warnings for the > same identifier. However, that seems better than missing cases like the > __pid_t you mentioned above. > > > My heuristic about -isystem would prevent flagging usage of reserved names > > resulting from implementations of system headers - for instance, if a macro > > in > > a system header used __uint32_t because it needs to avoid making uint32_t > > visible. > > Right. That seems like the same heuristic documented at > http://gcc.gnu.org/onlinedocs/cpp/System-Headers.html that I referenced in > comment 7: "Macros defined in a system header are immune to a few warnings > wherever they are expanded."
