CODEWITHSUNDEEP
cgccc-preprocessorcmockc-header
sandeep akkanapragada
sandeep akkanapragada

Reputation: 11

how to use gcc to preprocess header only for #ifdef, not for #include and #defines

I have to preprocess a header, during this I want to only process the header for #ifdef, #if defined sections, other sections like Macro expansion and #include sections should not be expanded or checked. how to get this? I need to pass this output file to another software like cmock to create a mock file and then use it for compilation. but the problem I am facing is if I use gcc -E it generates a file where all #includes are expanded, Macros expanded along with #if defines. any help would be appreciated

for example:

#include <stdint.h>   //i don't want to pre-process this line

#if defined (__MACRO_A__)  //i want to pre-process this line
    void funcA(void);
#else
    void funcB(void);
#endif

I want the output file to have only funcB prototype. I have not defined MACRO_A, so if I preprocess header only funcB is getting included, but all the #includes are getting expanded, which I don't want.

Upvotes: 1

Views: 518

Answers (1)

KamilCuk
KamilCuk

Reputation: 141155

but all the #includes are getting expanded, which I don't want.

So remove them from the file.

grep -v '#include' inputfile.c | gcc -E -xc -

The regex above can possibly be better.

Upvotes: 1

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