Question

I am having a situation where #define in one of the header files breaks an enum declaration in another header file.

Using -E switch on gcc I’ve established that I have

#define OFF 0

somewhere.

Question is, how do I find out where? The project is huge, dozens of include directories, hundreds of include files. I’ll do a global grep eventually, but the question is, is there any way to ask the gcc compiler where #define occurs? It obviously has that information!

Update: thanks for not one but two solutions – SO comes through.
Just for the record, the culprit was one of the Sybase client libraries’ includes (ctlib, not even dblib). Ouch.

Answer 1

You can redefine it (to a different value). Then the gcc will tell you where it is already defined.

On my system it looks like this:

In file included from < some file >:27,

             from < another file >:13: 

< header file with the redefined value>:30:1: > warning: “< the define >” redefined

< command-line >: warning: this is the location of the previous
definition