#redefine??

[MK27]

I'm trying to create a simple patch for a build tree that I didn't write. I need to change a hardcoded (#define) value to an int which can be adjusted during execution. I have checked all references to the variable in the source files and it is treated as an int when passed around, so I don't see a problem.

However, when I change the original definition (in a header file, nb) from "#define THISNUM 12" to "int ThisNum 12" (and replaced THISNUM with ThisNum everywhere to remain conventional), I get a bunch of "multiple definition" build errors (then the linker fails) from object files that use the sources (I'm not familiar with the make/build process on a whole tree of files).

What can I do?

ps. as a hack I added "extern" but still no dice...

[brewbuck]

Mucking with other people's #defines is dangerous.

Anyway...

#undef WHATEVER
#define WHATEVER BlahBlah

EDIT: Hmm. I misread your question.

You need this in the header file:

extern int ThisNum;

And in some module somewhere:

int ThisNum = 12;

Then replace:

#define THISNUM ThisNum

This is pretty awful.

[MK27]

Mucking with other people's #defines is dangerous.

This is pretty awful.

Yeah, it's not really intended as a permanent situation. Your solution works (extern int MyNum; #define MYNUM MyNum) in so far as I get a little further into the build and then get "undefined reference to MyNum".

I did add "MyNum=12" somewhere, but that should not matter w/r/t to the fact that MyNum will have some value anyway (I actually moved MyNum=12 to the line before the undefined reference, same problem).

Hack, yuck, hack, yuck, hack...

[brewbuck]

The undefined reference is probably because you never actually defined MyNum. You need to put this in exactly one .c module:

int MyNum = ...;

The extern declaration from the header file is not enough on its own to create the variable.

[MK27]

Sweet! Brewbuck you're my new hero.

Having never used extern before, I was using "Mynum =" instead of "int Mynum=" in the later definition.