How to let an executable depends on a plain text file?

[Freed-Wu]

Some C compiler allow user to pass a plain text file, such as

a.txt:

# comment
-O2
--gcc

cc @a.txt main.c

If we simply

add_project_arguments('@' + 'a.txt')
executable('demo', ['main.c'])

When we update a.txt, the demo will not be rebuilt.

If we

add_project_arguments('@' + 'a.txt')
executable('demo', ['main.c', 'a.txt'])

ERROR: No specified compiler can handle file /the/path/of/a.txt

How can we do?

[bonzini]

You can use link_depends in some cases, but not for sources or arguments to the compiler (for example include paths). If you are interested in adding arguments to the compiler or the linker, you should instead read the file and split it by word or line instead.

[eli-schwartz]

Such a Makefile would be weird because it doesn't actually depend on or use dep_file.txt and therefore it should not be rebuilt after all.

Also, your example Makefile shows dep_file.txt as a link-time dependency

[Freed-Wu]

If an executable depends on a file, when the file is modified (time stamp is changed), this executable must be rebuilt, In Makefile, It looks like:

main$(EXE): main.o
  cc $< -o $@
main.o: main.c dep_file.txt
  cc --some-option=dep_file.txt $< -c -o $@

Now How can I do same thing in meson?

[eli-schwartz]

Here is a worked Makefile example:

main$(EXE): main.o
	cc $< -o $@
main.o: main.c
	cc -include dep_file.txt $< -c -o $@ -MD -MF $@.d

-include *.d

Meson automatically handles -MD -MF for you, and automatically includes *.d as well. And main.o will always be rebuilt every time dep_file.txt is modified, due to those *.d files.

Please provide an example project where this does not work (one where you pass dep_file.txt as an argument which is NOT @dep_file.txt, but does not get rebuilt).

Avoid ambiguous examples such as --option=XXX.txt:

$ gcc --option=XXX.txt
gcc: error: unrecognized command-line option ‘--option=XXX.txt’

[bonzini]

Can you provide an actual example of what --some-option would be?

[Freed-Wu]

In my situation, C compiler is TI compiler, which use --cmd_file=XXX.cmd.