Do not link with OpenGL on Apple platforms

• Component: ANGLE
• Status: RESOLVED FIXED

[Keith Rollin]

OpenGL is not used in our build of ANGLE. Attempting to link with it causes warnings, which can turn to errors in some cases (in particular with building with Xcode's "new" build system).

[Radar WebKit Bug Importer]

<rdar://problem/61237956>

[Keith Rollin]

Created attachment 395337 [details]
Patch

[EWS Watchlist]

Note that there are important steps to take when updating ANGLE. See http://trac.webkit.org/wiki/UpdatingANGLE

[EWS]

Committed r259475: <https://trac.webkit.org/changeset/259475>

All reviewed patches have been landed. Closing bug and clearing flags on attachment 395337 [details].

[Kenneth Russell]

How are references to functions like CGLCreateContext resolved after this patch?

[Dean Jackson]

(In reply to Kenneth Russell from comment #5)
> How are references to functions like CGLCreateContext resolved after this
> patch?

Yeah. ANGLE only dynamically loads /System/Library/Frameworks/OpenGL.framework/Libraries/libGL.dylib

All the CGL stuff is in /System/Library/Frameworks/OpenGL.framework/Versions/A/OpenGL

So how did this pass tests?

[Dean Jackson]

Oh. It's because it is linked into WebCore which links OpenGL.

[Dean Jackson]

However, this change shouldn't have been necessary. If the new build system can't link against OpenGL, it can't build WebCore or WebKit.

[Dean Jackson]

Did you find out what was actually causing the compiler warning?

Because if it was unused functions when linking, then we also have a bunch of those in other projects.

e.g. 
ld: warning: linking with (/System/Library/Frameworks/CoreAudio.framework/CoreAudio) but not using any symbols from it
ld: warning: linking with (/System/Library/Frameworks/VideoToolbox.framework/VideoToolbox) but not using any symbols from it
ld: warning: linking with (/System/Library/Frameworks/CoreMedia.framework/CoreMedia) but not using any symbols from it
ld: warning: linking with (/System/Library/PrivateFrameworks/URLFormatting.framework/URLFormatting) but not using any symbols from it
ld: warning: linking with (/usr/lib/libAccessibility.dylib) but not using any symbols from it

[Keith Rollin]

(In reply to Dean Jackson from comment #8)
> However, this change shouldn't have been necessary. If the new build system
> can't link against OpenGL, it can't build WebCore or WebKit.

It's not that it can't link against OpenGL. I'm pretty sure that it's because it can't link against an OpenGL that doesn't exist. OpenGL.framework is not in the iphonesimulator SDK. That's where the error was occurring.

WebCore is able to link because it only links against OpenGL on the macOS:

WebCore.xcconfig
108:WK_OPENGL_LDFLAGS_iphoneos = -framework OpenGLES;
109:WK_OPENGL_LDFLAGS_iphonesimulator = -framework OpenGLES;
114:WK_OPENGL_LDFLAGS_maccatalyst = -framework OpenGL;
115:WK_OPENGL_LDFLAGS_macosx = -framework OpenGL;

Thanks for clarifying all of this. I was going crazy today trying to figure out how macOS was linking!