问题
I have a qmake file generated by Qt creator. I am modifying it but I do not manage to understand how to create a variable.
For example, I want to declare the library MYPATH as I did here:
MYPATH = /lib/aaa/bbb
unix:!macx:!symbian: LIBS += -L$(MYPATH)
When I run qmake I find in the generated makefile
LIBS = ....... -L$(MYPATH) .....
But the MYPATH variable is not declared anywhere.
Does anyone know how to declare such a variable properly?
回答1:
QMake uses its own syntax for variable references.
VAR = foobar=> Assign value to variable when qmake is run$$VAR=> QMake variable's value at the time qmake is run$${VAR}=> QMake variable's value at the time qmake is run (identical but enclosed to separate from surrounding text)$(VAR)=> Contents of an Environment variable at the time Makefile (not qmake) is run$$(VAR)=>Contents of an Environment variable at the time qmake (not Makefile) is run
Try it like this
MYPATH = /lib/aaa/bbb
unix:!macx:!symbian: LIBS += -L$${MYPATH}
回答2:
Other useful variable type: $$[...]
This means "configuration option that were set when Qt was built"
Example:
message($$[QT_INSTALL_BINS])
This gives:
C:\Qt\Qt5.0.2\5.0.2\msvc2010_opengl\bin
来源：https://stackoverflow.com/questions/7754218/qmake-how-to-add-and-use-a-variable-into-the-pro-file