Thanks Brian, The links are very helpful! About your comments, could you let me know what do you mean *There's no way to know based only on what you've given.* please? -------------------- As for why you'd want a file containing a list of all the #defines, you'd have to look at the context of how it's used elsewhere in the build system. There's no way to know based only on what you've given. -------------------- regards, George ----- Original Message ---- From: Brian Dessent <brian@xxxxxxxxxxx> To: Lin George <george4academic@xxxxxxxxx> Cc: gcc-help@xxxxxxxxxxx Sent: Friday, October 12, 2007 11:07:15 PM Subject: Re: gcc option -E Lin George wrote: > I have tried that in ListDef file (new generated after either of the two commands) and it contains several hundred lines of #define, typedef and some other definitions. Could anyone help to answer what is the function of the two commands? Differences between -dM and -dD? The -E option enables preprocessing only. Every option is documented in the manual: http://gcc.gnu.org/onlinedocs/gcc/Option-Index.html http://gcc.gnu.org/onlinedocs/gcc/Preprocessor-Options.html As for why you'd want a file containing a list of all the #defines, you'd have to look at the context of how it's used elsewhere in the build system. There's no way to know based only on what you've given. Brian ____________________________________________________________________________________ Tonight's top picks. What will you watch tonight? Preview the hottest shows on Yahoo! TV. http://tv.yahoo.com/