Merge LLVM's commit that fixes lld-link on Windows 7 and Wine

[SimonN]

Please include this commit from llvm-project upstream in the next LDC release. That commit fixes LDC issue #3675 -- lld-link fails to write any output at all -- on Windows 7, and likely also on Wine.

I use LDC in Wine as my Linux-to-Windows cross-compiling solution. As I explained in the (prematurely closed) LDC issue #3675, the current LDC 1.25.1 is broken in Wine; lld-link errors even on Hello World. Thus, I'm very interested that the upstream fix from LLVM gets merged into the next LDC. Likewise, the Windows 7 users will also be happy about the merge.

My broken LDC is:

LDC - the LLVM D compiler (1.25.1):
  based on DMD v2.095.1 and LLVM 11.0.1
  built with LDC - the LLVM D compiler (1.25.1)
  Default target: x86_64-pc-windows-msvc
  Host CPU: skylake

Example output from failing compiles of Hello World

[kinke]

The linked commit seems to fix something that landed in 12.0.0; unless it was also cherry-picked for LLVM 11.0.1, I doubt that it fixes the LLD issue.

A workaround for the time being is to download some working lld-link.exe (e.g., older versions of https://github.com/ldc-developers/llvm-project/releases) and use it via -linker=lld-link (e.g., in etc/ldc2.conf).

[SimonN]

In the description on LLVM Phabricator, fix author aganea says that this commit fixes the following two downstream bugs:

• LLVM Bug 48378 - wasm-ld fails in Windows 7
• Rust Bug 81051 - Starting with nightly-2021-01-13 (1.51) rustc fails to build archives on Windows 7 -- especially this one looks similar to the D Hello World LLD problem.

Then Rust Bug 82677 - Track Windows 7 vs. delete-on-close fixes says that aganea's fix resolves the llvm-ar problem.

How do LLVM fixes normally get into LDC, is there a manual selection or does it always depend on the latest LLVM backend?

Thanks for the workaround idea. I'll keep LDC 1.24 around for now, but breaking changes in the D language might happen anytime, so it's good to have this idea as a backup.

[thewilsonator]

How do LLVM fixes normally get into LDC

Official LDC releases are built with https://github.com/ldc-developers/llvm-project
You can always build LLVM yourself and build LDC against that, though you may need to do some alterations to druntime (updating versions and the like).

[kinke]

The mentioned commit was cherry-picked onto upstream's release/12.x branch and will thus be in 12.0.0 final (still not released...).

[SimonN]

In Wine 6.7, the same LDC 1.25.1 now works that failed in Wine 6.4. That solves my problem already before updating to the current LDC 1.26.0. Looks like Windows 7 and Wine shared an oddity that doesn't exist anymore in Win 8 and Win 10.

I'll re-test with LDC 1.26.0 on Wine 6.7 within 1-2 days and post results.

[kinke]

Official v1.26 builds still use LLVM 11.0.1, so I don't expect any difference.

[SimonN]

• Wine 6.4 + LDC 1.25.1 is the original bug.
• Wine 6.4 + LDC 1.26.0 has the same bug.
• Wine 6.4 + LDC 1.27.0-beta1 has the same bug: On compiling/linking Hello World, I get:

lld-link: error: failed to write the output file: Path is invalid.

• Wine 6.9 + LDC 1.25.1 works.
• Wine 6.9 + LDC 1.26.0 works.
• Wine 6.10 + LDC 1.27.0-beta1 works.

You've included aganea's commit exactly as this isssue suggests, thanks! For Wine, the commit turned out irrelevant. Wine 6.7 (or maybe 6.6 or 6.5) has its own fix, and that fix is the only important fix.

But for Windows 7, aganea's commit looks like it's really the fix: Hello World will now compile on Windows 7 using LDC 1.27.0-beta1 that is based on LLVM 12.0.0. Hello World didn't compile on Windows 7 with LDC 1.26.0.

Thus:

• Windows 7 users: Update to LDC 1.27.0-beta1 or newer.
• Wine users: Update to Wine 6.7 or newer. Any LDC should then work.