gcc disable - 特定文件/文件夹的标志

Question

I have some open source library files in my project (eg: http://nothings.org/stb_vorbis/stb_vorbis.c ). -Wall option is enabled in my Android.mk file. During compilation several warnings are generated in stb_vorbis.c.

warning: unused variable <var>
warning: statement with no effect
warning: <var> defined but not used
warning: <var> may be used uninitialized in this function

For some reason I do not want to modify stb_vorbis.c but still want the -Wall option to be available for my own source files. Is there any way to disable -Wall option for specific files/folder ?

Answer 1

Is there any way to disable -Wall option for specific files/folder ?

I do not believe there is any gcc option that could be used to achieve this. You need to change your Makefile that you used to compile the problematic source files.

You could do something like

CFLAGS:=$(filter-out -Wall, $(CFLAGS))

in the Makefile for stb_vorbis , if your make supports filter-out function.

Also you could write a specific rule for that stb_vorbis.c :

STB_VOBIS_CFLAGS:=$(filter-out -Wall, $(CFLAGS))
stb_vorbis.o: stb_vorbis.c ...
        $(CC) $(STB_VOBIS_CFLAGS) -o $@ -c $<

Answer 2

Although there's no way to turn off -Wall with one option, you can turn off specific warnings in GCC, using the -Wno-* for warning * . So, for example, to suppress the unused variable warning you can add -Wno-unused-variable . See http://gcc.gnu.org/onlinedocs/gcc/Warning-Options.html for more information on different warning options.

So for example you could use target-specific variables, like:

stb_vorbis.c: CFLAGS += -Wno-unused-variable

Answer 3

Using target-specific variables you can append the -w option to inhibit all warning messages for stb_vorbis.c file:

stb_vorbis.o: CFLAGS += -w

or for an entire directory:

third_party/%.o: CFLAGS += -w

A general rule of thumb is that if you have two or more mutually exclusive options, gcc will generally take later options over earlier ones.