update of 3aug2025 is not robust against circular includes in header files

[Peter Schops]

On 3aug2025 preprocessor and simplecpp got updated, and after this update cppcheck is failing to analyze real projects.

In cppcheck/test I added color.h, and that was enough to trigger the problem.

color.h includes fixture.h and fixture.h includes color.h again.
This is perfectly ok in regular c-code. And the preprocessor of the c-compiler we give a helping hand to protect itself with the #ifndef/#define or #pragma once. And before the update, cppcheck also did not have issues with circular includes.

#ifndef colorH
#define colorH

#include "fixture.h"
#include "precompiled.h"

#endif //colorH

I have no idea where to start to solve this issue. So I hope there is someone smarter then me that knows how to fix the issue.

I can say that when I take the last version, and replace simplecpp and preprocessor files with the version of 2aug2025, the issue is gone.

[Peter Schops]

Issue seems to be fixed now
Fix #14086 (simplecpp: Update to 1.5.2) (#7762)

https://github.com/danmar/simplecpp/blob/master/simplecpp.cpp
Fix infinite loop with circular includes (#497)