"Michael Gong" <mwgong@xxxxxxxxxxxxxx> writes: > It might be a basic question. I always think that the "#" directive in > the preprocessed file won't affect compilation, but following example > shows that I am wrong. Can anyone give a quick explanation ? > > /* t1.c */ > # 1 "foo.c" > # 1 "<built-in>" > # 1 "<command line>" > # 1 "foo.c" > # 1 "/usr/include/stdlib.h" 1 3 > # 25 "/usr/include/stdlib.h" 3 > # 1 "/usr/include/features.h" 1 3 > # 295 "/usr/include/features.h" 3 > # 1 "/usr/include/sys/cdefs.h" 1 3 > # 296 "/usr/include/features.h" 2 3 > # 318 "/usr/include/features.h" 3 > # 1 "/usr/include/gnu/stubs.h" 1 3 > # 319 "/usr/include/features.h" 2 3 > # 26 "/usr/include/stdlib.h" 2 3 > # 1 "/usr/lib/gcc-lib/i386-redhat-linux/3.2.3/include/stddef.h" 1 3 > # 213 "/usr/lib/gcc-lib/i386-redhat-linux/3.2.3/include/stddef.h" 3 > > typedef unsigned int size_t; > > extern void *malloc (size_t __size) __attribute__ ((__malloc__)); > char * malloc(); > > /* end of t1.c */ > > "t1.c" is compiled successfully to generate a ".o" file. > > But if I remove all the "#" directives, following error message will > be shown: > > t1.c:22: conflicting types for `malloc' > t1.c:21: previous declaration of `malloc' > > > Therefore, it shows that "#" directives does affect compilation. Is > that correct ? The '#' directives can disable some warnings. The '#' directives can indicate when compiling a system header file (the 3 at the end of the lines) and some warnings are suppressed in system header flies. However, the '#' directives should not suppress an error like this. It seems that you are using gcc 3.2.3, which is quite an old version. There may have been a bug back then. I tried your test case with the current compiler, and it does report an error with the '#' directives. Ian
