linker input file unused because linking not done - gcc

问题

I am a beginner in writing makefiles. I have a makefile something like this:

PATH1 = /ref

CC=gcc
LINK = gcc

INCLUDES = .
INCLUDES += -I/PATH1/inc \
        -I/$(PATH1)/abc/inc/ \
        -I/$(PATH1)/def/inc/ 


all: src_file

run: src_file

src_file: 
    $(CC) $(INCLUDES) -MM  /ref/abcd.c -o $@ 

clean:
    rm -f *.o src_file

If I do a make, I get the error:

linker input file unused because linking not done.

I read some similar posts in stackoverflow but couldn't get a solution. Could anybody please let me know what's wrong with my makefile? Thanks in advance.

回答1:

The culprit is the preprocessor option -MM. From gcc pre-processor options,

-M

Instead of outputting the result of preprocessing, output a rule suitable for make describing the dependencies of the main source file. The preprocessor outputs one make rule containing the object file name for that source file, a colon, and the names of all the included files, including those coming from -include or -imacros command line options.

Passing -M to the driver implies -E, and suppresses warnings with an implicit -w.

-MM

Like -M but do not mention header files that are found in system header directories, nor header files that are included, directly or indirectly, from such a header.

So effectively you are just preprocessing and hence no compilation and no linking and the resultant error.

来源：https://stackoverflow.com/questions/10486698/linker-input-file-unused-because-linking-not-done-gcc