Re: [Xen-devel] [PATCH v2] qemu: replace "" with <> in headers

[Kevin Wolf <kwolf@xxxxxxxxxx>]

Am 21.03.2018 um 15:46 hat Michael S. Tsirkin geschrieben:
> Our current scheme is to use
>  #include ""
> for internal headers, and
>  #include <>
> for external ones.
> 
> Unfortunately this is not based on compiler support: from C point of
> view, the "" form merely looks up headers in the current directory
> and then falls back on <> directories.
> 
> Thus, for example, a system header trace.h - should it be present - will
> conflict with our local trace.h

You're right that there is a conflict, even though only in one
direction: "trace.h" is unambiguously the local trace.h in our source
tree, but <trace.h> refers to the same local header rather than the
system header as you would expect.

An easy way to resolve this conflict would be using -iquote rather than
-I for directories in the source tree, so that <trace.h> unambiguously
refers to the system header and "trace.h" unambiguously refers to the
QEMU header.

> As another example of problems, a header by the same name in the source
> directory will always be picked up first - before any headers in
> the include directory.
> 
> Let's change the scheme: make sure all headers that are not
> in the source directory are included through a path
> starting with qemu/ , thus:
> 
>  #include <>
> 
> headers in the same directory as source are included with
> 
>  #include ""
> 
> as per standard.
> 
> This (untested) patch is just to start the discussion and does not
> change all of the codebase. If there's agreement, this will be
> run on all code to converting code to this scheme.

Renaming files is always painful. If that's the fix, the cure might be
worse than the disease. As far as I know, the conflict is only
theoretical, so in that case I'd say: If it ain't broke, don't fix it.

Kevin

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