Controlling the executions of CPP Preprocessor - c++

Question

I am using standard CPP to preprocess any C/CPP file.
I am using the below command for preprocessing:
cpp -idirafter <path_to_header_files> -imacros <sourcefile> <source_file> > <destination_file>
The above command is replacing all the macros with its corresponding implementations defined in header files.
If I want some specific MACROS containing a particular string (eg, ASSERT) should not replace by cpp preprocessor. ie, if any macro defined by the name of TC_ASSERT_EQ or TC_ASSERT_NEQ defined in some header files should not replace by preprocessor.
Is there any ways I can control this?

Answer 1

You can use predefined macros to work around this. You can pass different defines to cpp and gcc/g++ using -D parameters
For example your assertion header can look like my_assert.h:
#ifndef __my_assert_h__
#define __my_assert_h__
#if defined ASSERT_DEBUG
#define my_assert(expr) my_assert(expr) /* please dont touch my assertions */
#else
#define my_assert(expr) ((void)0U) /* Your assertion macro here */
#endif /* ASSERT_xxx */
#endif /* #ifndef __my_assert_h__ */
And your source files can be as before. For example test.c:
#include "my_assert.h"
#include <stdio.h>
void foo (int p) {
my_assert(p==1);
puts("Tralala\n");
}
int main (void) {
foo(1);
return 0;
}
With the above trick you can run
cpp -DASSERT_DEBUG test.c
While the compilation still works as before.
gcc test.c

Answer 2

I have used #pragma poison TC_ASSERT_EQ statements to pass the line without preprocessing.