Bug 63747

Summary:	Spec current metadata syntax
Product:	pkg-config	Reporter:	Dan Nicholson <dbn.lists>
Component:	src	Assignee:	Dan Nicholson <dbn.lists>
Status:	RESOLVED MOVED	QA Contact:
Severity:	normal
Priority:	medium	CC:	nenolod
Version:	unspecified
Hardware:	Other
OS:	All
Whiteboard:
i915 platform:		i915 features:
Bug Depends on:
Bug Blocks:	18815, 47996

Description Dan Nicholson 2013-04-20 01:51:12 UTC

pkg-config has a de-facto metadata syntax that it's held to for years now. This is well understood by people, but what exactly pkg-config will accept is not well documented. Furthermore, there are ways the metadata could be improved to add functionality, but changing the behavior would be really harmful since older versions wouldn't know how to cope with it. Here's a plan to deal with that:

1. A new optional field is added that declares what version of the pkg-config metadata syntax it uses. In the absence of this field, version 1 is assumed. My suggestion for the name is SpecVersion.

2. The currently accepted metadata is specified as version 1 so that .pc file writers know exactly pkg-config or any other program handling .pc files know what to write.

3. Release pkg-config-1.0 that covers version 1 of the metadata specification. After that, the metadata can be changed by bumping the spec version. .pc file writers can then opt-in to the newer syntax in a controlled way.

Michał Górny submitted a spec a while ago on the mailing list.

http://lists.freedesktop.org/archives/pkg-config/2012-September/000884.html

This document goes far beyond specifying the .pc metadata syntax. In particular, it specs the implementation details of the pkg-config program, which I don't think we want to get into. Still, it provides a solid starting point for a spec.

Comment 1 William Pitcock 2013-08-19 03:27:46 UTC

If I may interject, I believe a better approach would be to add a new virtual package.

Then you can do:

   Requires: pkgconfig-spec > 1

The current freedesktop implementation and pkgconf allow for multiple Requires: fields, so you can even do:

   Requires: pkgconfig-spec > 1
   [...]

Comment 2 William Pitcock 2013-08-19 03:31:00 UTC

In fact, I believe that this is the only possible way to do it, as a conformant implementation at present is required to ignore unsupported fields.

So, requiring a specific spec version in the dependency tree will cause the dependency tree to be incomplete, raising an error.

Comment 3 Dan Nicholson 2013-09-15 17:33:06 UTC

(In reply to comment #1)
> If I may interject, I believe a better approach would be to add a new
> virtual package.
> 
> Then you can do:
> 
>    Requires: pkgconfig-spec > 1
> 
> The current freedesktop implementation and pkgconf allow for multiple
> Requires: fields, so you can even do:
> 
>    Requires: pkgconfig-spec > 1
>    [...]

I like that idea, thanks.

Comment 4 GitLab Migration User 2018-08-25 12:55:54 UTC

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