[lld] [LLD][COFF] Don't dllimport from static libraries (PR #134443)
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Fri Apr 4 13:21:23 PDT 2025
llvmbot wrote:
<!--LLVM PR SUMMARY COMMENT-->
@llvm/pr-subscribers-lld-coff
Author: Alexandre Ganea (aganea)
<details>
<summary>Changes</summary>
This reverts commit 6a1bdd9 and re-instate behavior that matches what MSVC link.exe does, that is, error out when trying to dllimport a symbol from a static library.
We also now hint in stdout that we should rather dllimport the symbol from a import library.
Fixes https://github.com/llvm/llvm-project/issues/131807
---
Full diff: https://github.com/llvm/llvm-project/pull/134443.diff
5 Files Affected:
- (modified) lld/COFF/Driver.cpp (+2-4)
- (modified) lld/COFF/SymbolTable.cpp (+12-8)
- (modified) lld/COFF/SymbolTable.h (+1-4)
- (added) lld/test/COFF/imports-static-lib.test (+32)
- (removed) lld/test/COFF/undefined_lazy.test (-26)
``````````diff
diff --git a/lld/COFF/Driver.cpp b/lld/COFF/Driver.cpp
index 9bbab524b1f9a..7aa13bdce488e 100644
--- a/lld/COFF/Driver.cpp
+++ b/lld/COFF/Driver.cpp
@@ -2663,10 +2663,8 @@ void LinkerDriver::linkerMain(ArrayRef<const char *> argsArr) {
createECExportThunks();
// Resolve remaining undefined symbols and warn about imported locals.
- ctx.forEachSymtab([&](SymbolTable &symtab) {
- while (symtab.resolveRemainingUndefines())
- run();
- });
+ ctx.forEachSymtab(
+ [&](SymbolTable &symtab) { symtab.resolveRemainingUndefines(); });
if (errorCount())
return;
diff --git a/lld/COFF/SymbolTable.cpp b/lld/COFF/SymbolTable.cpp
index 16afcc64316e3..d1fb6e05a0320 100644
--- a/lld/COFF/SymbolTable.cpp
+++ b/lld/COFF/SymbolTable.cpp
@@ -231,6 +231,17 @@ void SymbolTable::reportUndefinedSymbol(const UndefinedDiag &undefDiag) {
}
if (numDisplayedRefs < numRefs)
diag << "\n>>> referenced " << numRefs - numDisplayedRefs << " more times";
+
+ // Hints
+ StringRef name = undefDiag.sym->getName();
+ if (name.starts_with("__imp_")) {
+ Symbol *imp = find(name.substr(strlen("__imp_")));
+ if (imp && imp->isLazy()) {
+ diag << "\nNOTE: a relevant symbol '" << imp->getName()
+ << "' is available in " << toString(imp->getFile())
+ << " but cannot be used because it is not a import library.";
+ }
+ }
}
void SymbolTable::loadMinGWSymbols() {
@@ -432,11 +443,10 @@ void SymbolTable::reportUnresolvable() {
reportProblemSymbols(undefs, /*localImports=*/nullptr, true);
}
-bool SymbolTable::resolveRemainingUndefines() {
+void SymbolTable::resolveRemainingUndefines() {
llvm::TimeTraceScope timeScope("Resolve remaining undefined symbols");
SmallPtrSet<Symbol *, 8> undefs;
DenseMap<Symbol *, Symbol *> localImports;
- bool foundLazy = false;
for (auto &i : symMap) {
Symbol *sym = i.second;
@@ -481,11 +491,6 @@ bool SymbolTable::resolveRemainingUndefines() {
imp = findLocalSym(*mangledName);
}
}
- if (imp && imp->isLazy()) {
- forceLazy(imp);
- foundLazy = true;
- continue;
- }
if (imp && isa<Defined>(imp)) {
auto *d = cast<Defined>(imp);
replaceSymbol<DefinedLocalImport>(sym, ctx, name, d);
@@ -513,7 +518,6 @@ bool SymbolTable::resolveRemainingUndefines() {
reportProblemSymbols(
undefs, ctx.config.warnLocallyDefinedImported ? &localImports : nullptr,
false);
- return foundLazy;
}
std::pair<Symbol *, bool> SymbolTable::insert(StringRef name) {
diff --git a/lld/COFF/SymbolTable.h b/lld/COFF/SymbolTable.h
index da19bf2800ecf..15e2644a6f519 100644
--- a/lld/COFF/SymbolTable.h
+++ b/lld/COFF/SymbolTable.h
@@ -67,10 +67,7 @@ class SymbolTable {
// Try to resolve any undefined symbols and update the symbol table
// accordingly, then print an error message for any remaining undefined
// symbols and warn about imported local symbols.
- // Returns whether more files might need to be linked in to resolve lazy
- // symbols, in which case the caller is expected to call the function again
- // after linking those files.
- bool resolveRemainingUndefines();
+ void resolveRemainingUndefines();
// Load lazy objects that are needed for MinGW automatic import and for
// doing stdcall fixups.
diff --git a/lld/test/COFF/imports-static-lib.test b/lld/test/COFF/imports-static-lib.test
new file mode 100644
index 0000000000000..63539cab9d860
--- /dev/null
+++ b/lld/test/COFF/imports-static-lib.test
@@ -0,0 +1,32 @@
+# REQUIRES: x86
+
+# Ensure that we don't import dllimport symbols from static (non-import) libraries
+# RUN: split-file %s %t.dir
+# RUN: llvm-mc --filetype=obj -triple=x86_64-windows-msvc %t.dir/foo.s -o %t.foo.obj
+# RUN: llvm-mc --filetype=obj -triple=x86_64-windows-msvc %t.dir/main.s -o %t.main.obj
+# RUN: llvm-lib %t.foo.obj -out:%t.foo.lib
+# RUN: not lld-link %t.foo.lib %t.main.obj -out:%t.dll -dll 2>&1 | FileCheck %s
+
+CHECK: error: undefined symbol: __declspec(dllimport) foo
+
+# Now do the same thing, but import the symbol from a import library.
+# RUN: llvm-mc --filetype=obj -triple=x86_64-windows-msvc %t.dir/foo_dll_main.s -o %t.foo_dll_main.obj
+# RUN: lld-link /out:%t.dll /dll %t.foo.obj %t.foo_dll_main.obj /export:foo /implib:%t.foo.imp.lib
+# RUN: lld-link %t.main.obj %t.foo.imp.lib -out:%t.exe -dll
+
+#--- foo.s
+.text
+.globl foo
+foo:
+ ret
+#--- foo_dll_main.s
+.text
+.global _DllMainCRTStartup
+_DllMainCRTStartup:
+ ret
+#--- main.s
+.text
+.global _DllMainCRTStartup
+_DllMainCRTStartup:
+ call *__imp_foo(%rip)
+ ret
diff --git a/lld/test/COFF/undefined_lazy.test b/lld/test/COFF/undefined_lazy.test
deleted file mode 100644
index ed5cd358b5cd9..0000000000000
--- a/lld/test/COFF/undefined_lazy.test
+++ /dev/null
@@ -1,26 +0,0 @@
-# REQUIRES: x86
-
-# RUN: split-file %s %t.dir
-# RUN: llvm-mc --filetype=obj -triple=x86_64-windows-msvc %t.dir/foo.s -o %t.foo.obj
-# RUN: llvm-mc --filetype=obj -triple=x86_64-windows-msvc %t.dir/bar.s -o %t.bar.obj
-# RUN: llvm-mc --filetype=obj -triple=x86_64-windows-msvc %t.dir/qux.s -o %t.qux.obj
-# RUN: llvm-lib %t.foo.obj -out:%t.foo.lib
-# RUN: llvm-lib %t.bar.obj -out:%t.bar.lib
-# RUN: lld-link %t.foo.lib %t.bar.lib %t.qux.obj -out:%t.dll -dll
-#
-#--- foo.s
-.text
-.globl foo
-foo:
- call bar
-#--- bar.s
-.text
-.globl bar
-bar:
- ret
-#--- qux.s
-.text
-.global _DllMainCRTStartup
-_DllMainCRTStartup:
- call *__imp_foo(%rip)
- ret
``````````
</details>
https://github.com/llvm/llvm-project/pull/134443
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