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

[Eric Blake <eblake@xxxxxxxxxx>]

On 03/19/2018 08:54 PM, Michael S. Tsirkin wrote:
> QEMU coding style at the moment asks for all non-system
> include files to be used with #include "foo.h".
[I'm replying without having read the rest of the thread, so bear with 
me if I repeat some of the other comments that have already been made]
And Markus even just did a cleanup along those lines.

> 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.
It's also nice when "file" means file belonging to our project, and 
<file> means 3rd-party file.  So we have to choose which semantics are 
easier; perhaps better Makefile rules that prevent us from seeing stale 
files is a better solution than figuring out which files are generated.
> As generated files are not in the search directory (unless the build
> directory happens to match the source directory),
Why can't we fix Makefile to include BOTH the build and the source 
directories (to pick up generated files first, and then 
version-controlled files), and possibly include logic to simplify to a 
single -I instead of two when doing in-tree builds?
> 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.
I'm not sure I'm a fan of this patch yet, if there may be other 
alternatives that solve the real issue of stale generated files breaking 
incremental builds.
--
Eric Blake, Principal Software Engineer
Red Hat, Inc.           +1-919-301-3266
Virtualization:  qemu.org | libvirt.org

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