[cairo-bugs] [Bug 73193] New: False positive warnings with gcc's -Wundef

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=73193

          Priority: medium
            Bug ID: 73193
          Assignee: chris at chris-wilson.co.uk
           Summary: False positive warnings with gcc's -Wundef
        QA Contact: cairo-bugs at cairographics.org
          Severity: normal
    Classification: Unclassified
                OS: All
          Reporter: self at brendanlong.com
          Hardware: Other
            Status: NEW
           Version: unspecified
         Component: general
           Product: cairo

Created attachment 91377
  --> https://bugs.freedesktop.org/attachment.cgi?id=91377&action=edit
Patch to set disabled feature macros to 0 instead of undefined

I'm trying to clean out gcc warnings in WebKitGTK, and running into this one:

In file included from
../../Source/WebCore/platform/graphics/cairo/CairoUtilities.cpp:42:0:
/usr/include/cairo/cairo-gl.h:113:5: error: "CAIRO_HAS_WGL_FUNCTIONS" is not
defined [-Werror=undef]
 #if CAIRO_HAS_WGL_FUNCTIONS

Theoretically, gcc shouldn't be complaining about this because Cairo is a
system library, but it does, and I can't figure out why (the -I lines are from
pkg-config so I can't easily fix them). The easiest solution seems to be to fix
this in Cairo.

The attached patch defines all undefined feature flags to 0. I tried to keep
the semantics exactly the same, and as similar as possible to the original
output, so if that's not necessarily I could simply if it more:

  * The current version has lines like this:

        /*#undef CAIRO_HAS_WGL_FUNCTIONS */

    I assume this so users can `#define CAIRO_HAS_WGL_FUNCTIONS 1` and override
the default. To have the same semantics, I wrapped by definitions in `#ifndef`
checks.

  * There's a fairly complex `for` loop to keep the disabled features list
sorted (since sorting the entire output would put the #defines first, then the
#endifs, then the #ifndefs..).

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