Re: [Xen-devel] [Qemu-block] [PATCH] qemu: include generated files with <> and not ""

[Stefan Hajnoczi <stefanha@xxxxxxxxx>]

On Tue, Mar 20, 2018 at 03:54:36AM +0200, Michael S. Tsirkin wrote:
> QEMU coding style at the moment asks for all non-system
> include files to be used with #include "foo.h".
> However this rule actually does not make sense and
> creates issues for when the included file is generated.
> 
> In C, include "file" means look in current directory,
> then on include search path. Current directory here
> means the source file directory.
> By comparison include <file> means look on include search path.
> 
> As generated files are not in the search directory (unless the build
> directory happens to match the source directory), it does not make sense
> to include them with "" - doing so is merely more work for preprocessor
> and a source or errors if a stale file happens to exist in the source
> directory.
> 
> This changes include directives for all generated files, across the
> tree. The idea is to avoid sending a huge amount of email.  But when
> merging, the changes will be split with one commit per file, e.g. for
> ease of bisect in case of build failures, and to ease merging.
> 
> Note that should some generated files be missed by this tree-wide
> refactoring, it isn't a big deal - this merely maintains the status quo,
> and this can be addressed by a separate patch on top.

Stale header files are a pain.  I often do make distclean before
checking out a radically different QEMU version to avoid the problem.

This patch trades off the stale header file issue for a new approach to
using <> vs "", which will be hard to use consistently in the future
since it is unconventional.

Is the build time improvement worth it (please post numbers)?

Stefan

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