Use --always-make when running make -n, where possible

[NobodyXu]

Motivation:

Suppose you have a complex project that you'd like to enable ale_c_parse_makefile.

Now after editing the file, you run make then run the executable, and find the result to be unsatisfactory.

Then you enter vim again to edit the file, only to find there is plenty of errors due to the fact that make -n no longer "run" the recipe for the source file.

Solution:

A simple solution will be to run make -n -W % instead of make -n to ensure that recipe for the source file is always "run".

This would fix the confusing behavior after make.

[w0rp]

How does make -n -W % work? What does it do? The arguments for make and the syntax Makefiles themselves are very esoteric.

[NobodyXu]

make -W % would pretend that source file % is not up-to-date, even when it is already up-to-date.

Suppose that there is two file, a.c and Makefile.

Using the Makefile, a.o is built. Due to the fact that a.o is updated, make -n outputs nothing and thus ale cannot use make -n to auto-detect the compiler flags.

Supplying -W a.c would make make -n output what if a.o is outdated and prints out the recipe for building it, thus making ale able to collect the compiler flags used to build a.c.

[NobodyXu]

ale can take advantage of this feature, run make -n -W % to extract the compiler flags, where % is the filename of the current buffer.

[w0rp]

I understand the issue, though I don't think what you've suggested will work. If I run make -n | grep /bin/cc for my xmms2-mpris project, I see this at first.

/usr/bin/cc  -I/usr/include/xmms2 -I/usr/include/gio-unix-2.0 -I/usr/include/glib-2.0 -I/usr/lib/x86_64-linux-gnu/glib-2.0/include   -o CMakeFiles/xmms2-mpris.dir/src/xmms2-mpris.c.o   -c /home/w0rp/git/xmms2-mpris/src/xmms2-mpris.c
/usr/bin/cc  -I/usr/include/xmms2 -I/usr/include/gio-unix-2.0 -I/usr/include/glib-2.0 -I/usr/lib/x86_64-linux-gnu/glib-2.0/include   -o CMakeFiles/xmms2-mpris.dir/src/mpris-object.c.o   -c /home/w0rp/git/xmms2-mpris/src/mpris-object.c
...

If I run make and then make -n | grep /bin/cc again, I get nothing. If I run make -n -W src/xmms2-mpris.c | grep /bin/cc, I still get nothing. make -Bn | grep /bin/cc, however, will provide output. This old pull request was created a while ago, which used that flag, and at the time I asked for it to be tested on BSD, as -B has a completely different meaning on BSD.

If there's a way to detect if the system is Linux instead of BSD in Vim, without a synchronous system call, we can use -B on Linux.

[w0rp]

I think I'm just going to use -B if the OS is a Unix variant, but isn't Mac OSX, which is easy to detect, and offer an option to turn it off for the extreme minority of users that use a BSD OS.

[NobodyXu]

That sounds quite good for me.

[w0rp]

--always-make is used by default on Linux and BSD now. BSD users will probably have to use let g:ale_c_always_make = 0 for make -n parsing to work. There's no way to avoid breaking BSD make without making ALE worse on all other systems. If you use BSD, just set that option too.