On Sun, 2011-10-02 at 21:05 +0200, Roman B. wrote: > Hi, > > $ cpp file.c > > alway outputs > > # 1 "file.c" > # 1 "<built-in>" > # 1 "<command-line>" > # 1 "file.c" > > Where as words are self-explanatory I cannot understand the meaning in > the whole. I could not find any explanation in the documentation also. > > So what do those 4 lines actually mean? They specify source locations. The first and last line says that what follows is line #1 of file.c The other lines specify line numbers for "virtual" files. The reason you see nothing in the is that you see the output of the preprocessor. If you add -dD to the preprocessor command line it will retain all #defines in the output. Try it again with 'gcc -E -dD file.c | more' to see all the builtin defines after the <built-in> header. Try to add a -DSOME=VALUE to see something in the <command-line> section. I hope this makes it clearer. The reason the #line-no parts are retained is that this is how a #line directive looks after preprocessing and so that really is directives to the compiler. All of this is described in the cpp manual, try info cpp. /MF
