On Wed, Jul 09, 2008 at 03:56:21PM -0400, Bradley Hanna wrote: > I am trying to define a variable that needs to be manipulated by one c > file in the kernel and read by another c file in a different directory. > I have defined the variable in a header file that is #included in both c > files. The problem is when I compile the kernel I get an error saying > that the variable cannot be defined more than once. I added a > preprocessor condition like this: > > #ifndef _NEW_HEADER_H > #define _NEW_HEADER_H > > //define the variable > > #endif > > it was my assumption that the variable would only be defined once > because of this macro but I am still having the same problems. > > How do I create header files that can be #included in multiple c files > like the files in the source tree? Standard C problem with a standard solution. You define the variable in a single C file and declare it in the header file with the keyword extern. So foo.c has: int bar; And foo.h has: extern int bar; If baz.c wants to use the variable bar, it will only have to include foo.h: #include "foo.h" /* ... */ bar = 42; Erik -- Erik Mouw -- mouw@xxxxxxxxxxxx
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