Properties, C/C++ Settings, Tools Settings, GCC Compiler, Preprocessor

Set the preprocessor options for your build configuration

Option Description
Do not search system directories (-nostdinc) Do not search the standard system directories for header files. Only the directories you have specified with -I options (and the directory of the current file, if appropriate) are searched.
Preprocess only (-E) Stop after the preprocessing stage; do not run the compiler proper. The output is in the form of preprocessed source code, which is sent to the standard output. Input files that don’t require preprocessing are ignored.
Defined symbols (-D) Predefine macro
Undefined symbols (-U) Cancel any previous definition of macro, either built in or provided with a -D option.