Allow passing /manifestdependency via #pragma comment(linker, ...)

[ColinFinck]

Summary

Linker commands added via #pragma comment(linker, ...) are passed to the linker via a .drectve section.
Current lld-link however rejects /manifestdependency arguments passed this way.
They are very common for enabling Visual Styles in Win32 GUI applications.

I have found https://bugs.llvm.org/show_bug.cgi?id=38797 opened over 2 years ago along with a simple one-liner patch.
I've updated this patch for latest lld as the bug still persists.

I have no LLVM commit access, so someone else has to commit this.
My author information: Colin Finck <[e-mail]>

Other involved authors from the bug report:

• Roland Reichwein <[e-mail]>
• Jaromir Kuba <[e-mail]>

[ColinFinck]

CC @rnk @sbc100 @aganea @thakis

[aganea]

@ColinFinck Would you mind adding test coverage for this? Either modify an existing test such as lld/test/COFF/directives.s or a add a new test.

[rnk]

Your change will ignore these flags, though, and I don't think that's what MSVC will do, from looking at the docs.

As I understand it, it looks like we process manifest files at the very end, after we've loaded all objects in the usual fixpoint way, so I think we should go ahead and implement this flag, rather than ignoring it as a stop-gap.

[pravic]

In D96862#2611861, @rnk wrote:

As I understand it, it looks like we process manifest files at the very end, after we've loaded all objects in the usual fixpoint way, so I think we should go ahead and implement this flag, rather than ignoring it as a stop-gap.

@rnk Any update on that?

[rnk]

I don't have plans to work on this, but it's a pretty straightforward starter project if anyone is interested.

[pravic]

In D96862#2785942, @rnk wrote:

I don't have plans to work on this, but it's a pretty straightforward starter project if anyone is interested.

Sounds appealing. Any guidance for a volunteer?

[thakis]

This patch here isn't quite enough. I fixed this in https://reviews.llvm.org/rG400a1de3ac4583794797852aab49aaa821c95b7d You can close this patch.

lld/COFF/Driver.cpp

case OPT_subsystem: {
         config->minorOSVersion = config->minorSubsystemVersion;
       }
       break;
     }
     // Only add flags here that link.exe accepts in
     // `#pragma comment(linker, "/flag")`-generated sections.
     case OPT_editandcontinue:
     case OPT_guardsym:
+    case OPT_manifestdependency:
     case OPT_throwingnew:
       break;
     default:
       error(arg->getSpelling() + " is not allowed in .drectve");
     }
   }
 }