Bug 312258 – inspector.gresource differs depending on the compiler used, breaking multiarch

• Component: WebKitGTK
• Status: RESOLVED FIXED

[Alberto Garcia]

This is what happens:

1. During compilation the InspectorBackendCommands.js.in file is generated

This contains several #if blocks, for example:

  #if defined(ENABLE_WEBGL) && ENABLE_WEBGL
  InspectorBackend.registerEnum("Canvas.ProgramType", {Compute: "compute", Render: "render"});
  #endif // defined(ENABLE_WEBGL) && ENABLE_WEBGL

2. This is run through the C preprocessor to generate InspectorBackendCommands.js

   clang -E -P -x c++ -C -DENABLE_FOO -DENABLE_BAR InspectorBackendCommands.js.in

3. The resulting file is added to inspector.gresource

In step (2), gcc is used if clang is not available, but unfortunately,
and due to the -C flag, gcc adds to the generated file several
comments from /usr/include/stdc-predef.h, e.g.:

   /* wchar_t uses Unicode 10.0.0.  Version 10.0 of the Unicode Standard is
      synchronized with ISO/IEC 10646:2017, fifth edition, plus
      the following additions from Amendment 1 to the fifth edition:
      - 56 emoji characters
      - 285 hentaigana
      - 3 additional Zanabazar Square characters */

clang does not do that, so depending on the compiler used to build
WebKit the arch-independent inspector.gresource varies depending
on the architecture, breaking multiarch installations.

Removing the -C flag is not the best option since it would strip the
actual comments from InspectorBackendCommands.js.in (including the
License and the Apple copyright notice).

One alternative is to use -ffreestanding, supported by both gcc and
clang, which does not use the standard library and therefore does not
bring anything from stdc-predef.h. Since we're using the preprocessor
to check for WebKit's own ENABLE_* and WTF_PLATFORM_* this should not
have any effect.

[Alberto Garcia]

Pull request: https://github.com/WebKit/WebKit/pull/62723

[EWS]

Committed 311268@main (2012029f8a67): <https://commits.webkit.org/311268@main>

Reviewed commits have been landed. Closing PR #62723 and removing active labels.