Auto merge of #125417 - lqd:lld-retry, r=<try>

bors · bors · commit 5572f385cb1b · 2024-05-22T17:23:15.000Z
self-contained linker: retry linking without `-fuse-ld=lld` on CCs that don't support it For the self-contained linker, this PR applies [the strategy](#125330 (comment)) of retrying the linking step when the driver doesn't support `-fuse-ld=lld`, but with the option removed. This is the same strategy we already use of retrying when e.g. `-no-pie` is not supported. Fixes #125330 r? `@petrochenkov` I have no idea how we could add a test here, much like we don't have one for `-no-pie` or `-static-pie` -- let me know if you have ideas -- but I tested on a CentOS7 image: ```console [root@d25b38376ede tmp]# ../build/host/stage1/bin/rustc helloworld.rs WARN rustc_codegen_ssa::back::link The linker driver does not support `-fuse-ld=lld`. Retrying without it. [root@d25b38376ede tmp]# readelf -p .comment helloworld String dump of section '.comment': [ 0] GCC: (GNU) 4.8.5 20150623 (Red Hat 4.8.5-44) [ 2d] rustc version 1.80.0-dev ``` (I wasn't able to test with `cross` as the issue describes: I wasn't able to reproduce that behavior locally. So I'll ask for help from the OP with a try build)
diff --git a/compiler/rustc_codegen_ssa/src/back/link.rs b/compiler/rustc_codegen_ssa/src/back/link.rs
@@ -799,6 +799,27 @@ fn link_natively(
             continue;
         }
 
+        // Check if linking failed with an error message that indicates the driver didn't recognize
+        // the `-fuse-ld=lld` option. If so, re-perform the link step without it. This avoids having
+        // to spawn multiple instances on the happy path to do version checking, and ensures things
+        // keep working on the tier 1 baseline of GLIBC 2.17+. That is generally understood as GCCs
+        // circa RHEL/CentOS 7, 4.5 or so, whereas lld support was added in GCC 9.
+        if matches!(flavor, LinkerFlavor::Gnu(Cc::Yes, Lld::Yes))
+            && unknown_arg_regex.is_match(&out)
+            && out.contains("-fuse-ld=lld")
+            && cmd.get_args().iter().any(|e| e.to_string_lossy() == "-fuse-ld=lld")
+        {
+            info!("linker output: {:?}", out);
+            warn!("The linker driver does not support `-fuse-ld=lld`. Retrying without it.");
+            for arg in cmd.take_args() {
+                if arg.to_string_lossy() != "-fuse-ld=lld" {
+                    cmd.arg(arg);
+                }
+            }
+            info!("{:?}", &cmd);
+            continue;
+        }
+
         // Detect '-static-pie' used with an older version of gcc or clang not supporting it.
         // Fallback from '-static-pie' to '-static' in that case.
         if matches!(flavor, LinkerFlavor::Gnu(Cc::Yes, _))
