Re: [PATCH] Fix compiler message generation

[Michal Marek]

On Wed, Jul 02, 2014 at 11:56:46AM +0100, David Howells wrote:
> The following commit:
> 
> 	commit 9da0763bdd82572be243fcf5161734f11568960f
> 	Author: Michal Marek <mmarek@xxxxxxx>
> 	Date:   Fri Apr 25 23:25:18 2014 +0200
> 	Subject: kbuild: Use relative path when building in a subdir of the source tree
> 
> makes compiler messages relative to the *build* tree if the build tree is a
> subdirectory at the root of the source tree.
> 
> This is the wrong thing to do since the make command is issued in the *source*
> tree and so any editor or IDE that issues the make command will likely expect
> paths in warnings and errors to be relative either to the current directory at
> the time the make was issued or to the directory in which make was run.
> 
> Certainly, this is something I'm seeing with emacs.  I do:
> 
> 	LANG=C nice -19 make O=build -C /data/fs/linux-2.6-fscache -j4
> 
> And then I get error messages that look like:
> 
> 	../fs/namei.c: In function 'SYSC_linkat':
> 	../fs/namei.c:4836:57: error: expected declaration specifiers before 'x'
> 		int, newdfd, const char __user *, newname, int, flags)x
> 
> which emacs can't find the source for because it doesn't relate to anything
> emacs knows about.
> 
> As a temporary measure, fix this by substituting the full path of the source
> as make knows it.

Boaz Harrosh hit the same problem with kdevelop and posted a patch that
adds a variable to turn off relative paths:
https://lkml.org/lkml/2014/6/19/295. This has the downside that one has
to remember to set the variable.

However, VPATH builds are not that uncommon, so I guess the editors and
IDEs can actually handle them if make prints the "Entering directory
`blah/blah'" messages. We disable this in kbuild to not pollute the log,
but how about the following patch? I tried it with vim and it worked: