Created attachment 157510 [details]
internal PP states

The conditional preprocessing of system/user header files is confused when a change of user macros should affect the parsed content of header files.


I reproduced this using NetBeans Dev 201511260002.
Find attached a report of internal PP states.

A. System setup:
I reproduced using Windows x64 and Cygwin x64, but it is something that will most likely also occur on Linux/Mac.

For clearer steps create a simple "problem.h" header file with following content:
#ifdef PROBLEM_MACRO
int  PROBLEM;
#endif

B. Reproduction steps:
0. add "problem.h" header file to a system include path folder that will be used. In my case: (c:\cygwin64\lib\gcc\x86_64-pc-cygwin\4.9.2\include\c++\)
1. create a new sample project "Welcome" for C++ using Cygwin toolchain. remove include statement and all content from main function except for return statement. For more clarity.
2. To reproduce this in 2 scenarios, copy "problem.h" file also to the base folder of the new project.
3. edit Welcome.cc to add: "PROBLEM;" inside main function. Error reported, as expected.
3. under Debug Configuration, C++ Compiler options add a user macro (preprocessor definition) "PROBLEM_MACRO". Press Apply. Error still there, as expected because we did not add a include statement.
4. Now add #include "problem.h" inside Welcome.cc. Error goes away, as expected. Ctrl-click takes us to correct location.
5. Build project, no problems.
6!!. Delete include statement. No error is shown in the IDE.
7!!. Add include statement to point to the system header file: #include <problem.h>. Ctrl-click still takes us to project folder header file.
8. Delete include statement, no error.
9. Build project and see that it fails, as expected. Due to Action Items view related funcitonality, error appears (build error).

10!! Now create a new project, similar to the former one, but do not add any new include statements or user macros. Just add "PROBLEM;" to the main function and notice how no error is being shown.