What do the following instructions?
win32:!win32-g++{ #?????
QMAKE_CXXFLAGS += -openmp #?????
QMAKE_LFLAGS += -openmp #?????
QMAKE_CXXFLAGS+= -fopenmp #?????
QMAKE_LFLAGS += -fopenmp #?????
QMAKE_CXXFLAGS is defined as:
Specifies the C++ compiler flags for building a project. The value of this variable is typically handled by qmake or qmake.conf and rarely needs to be modified.
OpenMP (Open Multi-Processing) is an application programming interface (API) that supports multi-platform shared memory multiprocessing programming in C, C++, and Fortran.
I do not understand why in some instructions it appears -openmp and in others -fopenmp.
when is it necessary to use QMAKE_CXX and how do I know what value or variable (openmp) should I add?