http://gcc.gnu.org/bugzilla/show_bug.cgi?id=60100
Bug ID: 60100 Summary: warning disappears when preprocessed source is compiled Product: gcc Version: 4.8.1 Status: UNCONFIRMED Severity: normal Priority: P3 Component: c Assignee: unassigned at gcc dot gnu.org Reporter: lavr at ncbi dot nlm.nih.gov Created attachment 32070 --> http://gcc.gnu.org/bugzilla/attachment.cgi?id=32070&action=edit GCC specs are attached Hello, When compiling the attached C code with GCC 4.8.1, I see a warning (which is correct) that the callback signature mismatches what's expected in the argument of BUF_PeekAtCB() call. If however, the source is first preprocessed then compiled, there is no warning! Since distcc uses precompiled source, the disappearing warning is a bad thing because it hides potential (and real, such as this case) bugs. $ cat qq.h #include <stddef.h> typedef struct SBUF* BUF; extern size_t BUF_PeekAtCB (BUF buf, size_t pos, size_t (*callback)(void* cbdata, const void* buf, size_t size), void* cbdata, size_t size ); $ cat qq.c #include <stdio.h> #include "qq.h" size_t cb(void* a, void* b, size_t c, int d) { return c; } int main() { BUF b = 0; size_t n = BUF_PeekAtCB(b, 0, cb, 0, 512); printf("%u\n", (unsigned int) n); return 0; } $ gcc -Wall -c qq.c -o qq.o qq.c: In function 'main': qq.c:14:5: warning: passing argument 3 of 'BUF_PeekAtCB' from incompatible pointer type [enabled by default] size_t n = BUF_PeekAtCB(b, 0, cb, 0, 512); ^ In file included from qq.c:2:0: qq.h:7:15: note: expected 'size_t (*)(void *, const void *, size_t)' but argument is of type 'size_t (*)(void *, void *, size_t, int)' extern size_t BUF_PeekAtCB ^ $ gcc -Wall -E qq.c -o qq.e $ gcc -Wall -c qq.e -o qq.o gcc: warning: qq.e: linker input file unused because linking not done Also, I'm not sure why there is a bogus warning about linking here (and not when compiling right from the source file, above). Any insight that you may have provide will be highly appreciated. Thanks, Anton Lavrentiev