[LLD][COFF] Allow additional attributes in forwarding exports.

[cjacek]

Testing with MSVC link.exe showed that it respects such options, while LLD currently discards them.

I noticed it while working on adding support for EXPORTAS parameter and needed to decide what to do about this early return.

[llvmbot]

@llvm/pr-subscribers-platform-windows
@llvm/pr-subscribers-lld

@llvm/pr-subscribers-lld-coff

Author: Jacek Caban (cjacek)

Changes

Testing with MSVC link.exe showed that it respects such options, while LLD currently discards them.

I noticed it while working on adding support for EXPORTAS parameter and needed to decide what to do about this early return.

---

Full diff: https://github.com/llvm/llvm-project/pull/86535.diff

2 Files Affected:

• (modified) lld/COFF/DriverUtils.cpp (+6-7)
• (modified) lld/test/COFF/export.test (+30-3)

diff --git a/lld/COFF/DriverUtils.cpp b/lld/COFF/DriverUtils.cpp
index fc8eb327be49bd..0fa4769bab19db 100644
--- a/lld/COFF/DriverUtils.cpp
+++ b/lld/COFF/DriverUtils.cpp
@@ -577,16 +577,15 @@ Export LinkerDriver::parseExport(StringRef arg) {
     if (y.contains(".")) {
       e.name = x;
       e.forwardTo = y;
-      return e;
+    } else {
+      e.extName = x;
+      e.name = y;
+      if (e.name.empty())
+        goto err;
     }
-
-    e.extName = x;
-    e.name = y;
-    if (e.name.empty())
-      goto err;
   }
 
-  // If "<name>=<internalname>[,@ordinal[,NONAME]][,DATA][,PRIVATE]"
+  // Optional parameters "[,@ordinal[,NONAME]][,DATA][,PRIVATE]"
   while (!rest.empty()) {
     StringRef tok;
     std::tie(tok, rest) = rest.split(",");
diff --git a/lld/test/COFF/export.test b/lld/test/COFF/export.test
index d340e0174b563e..7b804852e6d34a 100644
--- a/lld/test/COFF/export.test
+++ b/lld/test/COFF/export.test
@@ -76,18 +76,45 @@ SYMTAB: exportfn3 in export.test.tmp.DLL
 
 # RUN: lld-link /out:%t.dll /dll %t.obj /export:foo=kernel32.foobar
 # RUN: llvm-objdump -p %t.dll | FileCheck --check-prefix=FORWARDER %s
+# RUN: llvm-nm -M %t.lib | FileCheck --check-prefix=SYMTAB-FWD %s
 
 # RUN: echo "EXPORTS foo=kernel32.foobar" > %t.def
-# RUN: lld-link /out:%t.dll /dll %t.obj /def:%t.def
-# RUN: llvm-objdump -p %t.dll | FileCheck --check-prefix=FORWARDER %s
+# RUN: lld-link /out:%t-def.dll /dll %t.obj /def:%t.def
+# RUN: llvm-objdump -p %t-def.dll | FileCheck --check-prefix=FORWARDER %s
+# RUN: llvm-nm -M %t-def.lib | FileCheck --check-prefix=SYMTAB-FWD %s
 
 FORWARDER: Export Table:
-FORWARDER:  DLL name: export.test.tmp.dll
+FORWARDER:  DLL name: export.test.tmp
 FORWARDER:  Ordinal base: 1
 FORWARDER:  Ordinal      RVA  Name
 FORWARDER:        1   0x1010  exportfn
 FORWARDER:        2           foo (forwarded to kernel32.foobar)
 
+SYMTAB-FWD: __imp_exportfn3 in export.test.tmp
+SYMTAB-FWD: __imp_foo in export.test.tmp
+SYMTAB-FWD: exportfn3 in export.test.tmp
+SYMTAB-FWD: foo in export.test.tmp
+
+# RUN: lld-link /out:%t-fwd-priv.dll /dll %t.obj /export:foo=kernel32.foobar,DATA,PRIVATE
+# RUN: llvm-objdump -p %t-fwd-priv.dll | FileCheck --check-prefix=FORWARDER %s
+# RUN: llvm-nm -M %t-fwd-priv.lib | FileCheck --check-prefix=SYMTAB-FWD-PRIV %s
+
+SYMTAB-FWD-PRIV:     __imp_exportfn3 in export.test.tmp-fwd-priv
+SYMTAB-FWD-PRIV-NOT: __imp_foo
+SYMTAB-FWD-PRIV:     exportfn3 in export.test.tmp-fwd-priv
+SYMTAB-FWD-PRIV-NOT: foo
+
+# RUN: lld-link /out:%t-fwd-ord.dll /dll %t.obj /export:foo=kernel32.foobar,@3,NONAME
+# RUN: llvm-objdump -p %t-fwd-ord.dll | FileCheck --check-prefix=FORWARDER-ORD %s
+# RUN: llvm-nm -M %t-fwd-ord.lib | FileCheck --check-prefix=SYMTAB-FWD %s
+
+FORWARDER-ORD: Export Table:
+FORWARDER-ORD:  DLL name: export.test.tmp-fwd-ord.dll
+FORWARDER-ORD:  Ordinal base: 3
+FORWARDER-ORD:  Ordinal      RVA  Name
+FORWARDER-ORD:        3           (forwarded to kernel32.foobar)
+FORWARDER-ORD:        4   0x1010  exportfn3
+
 # RUN: lld-link /out:%t.dll /dll %t.obj /merge:.rdata=.text /export:exportfn1 /export:exportfn2
 # RUN: llvm-objdump -p %t.dll | FileCheck --check-prefix=MERGE --match-full-lines %s
 

[github-actions]

✅ With the latest revision this PR passed the Python code formatter.

[github-actions]

✅ With the latest revision this PR passed the C/C++ code formatter.

[mstorsjo]

This LGTM, thanks!

Does the same work in llvm-dlltool and/or llvm-lib /def: as well, or do we need to do some corresponding change there?

[cjacek]

Does the same work in llvm-dlltool and/or llvm-lib /def: as well, or do we need to do some corresponding change there?

It should already work with llvm-dlltool and llvm-lib. .def file parser already support those cases and importlib writer handles them.

[MaskRay]

Useful to add -NEXT in case they are adjacent. When things go wrong, -NEXT provides a better diagnostic

[cjacek]

I added -NEXT and pushed. Thanks for reviews.