[lld] [LLD][COFF] Don't dllimport from static libraries (PR #134443)
Alexandre Ganea via llvm-commits
llvm-commits at lists.llvm.org
Fri Apr 4 14:54:40 PDT 2025
https://github.com/aganea updated https://github.com/llvm/llvm-project/pull/134443
>From f1f1909a68ca78740a19537d1db966713b558efb Mon Sep 17 00:00:00 2001
From: Alexandre Ganea <alex_toresh at yahoo.fr>
Date: Fri, 4 Apr 2025 16:03:05 -0400
Subject: [PATCH 1/2] [LLD][COFF] Don't dllimport from static libraries
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
---
lld/COFF/Driver.cpp | 6 ++---
lld/COFF/SymbolTable.cpp | 20 ++++++++++-------
lld/COFF/SymbolTable.h | 5 +----
lld/test/COFF/imports-static-lib.test | 32 +++++++++++++++++++++++++++
lld/test/COFF/undefined_lazy.test | 26 ----------------------
5 files changed, 47 insertions(+), 42 deletions(-)
create mode 100644 lld/test/COFF/imports-static-lib.test
delete mode 100644 lld/test/COFF/undefined_lazy.test
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
>From 593bfe8d895459a9b1b6c4924b1cb28fbde996cc Mon Sep 17 00:00:00 2001
From: Alexandre Ganea <alex_toresh at yahoo.fr>
Date: Fri, 4 Apr 2025 17:54:14 -0400
Subject: [PATCH 2/2] Simplify & add a test case
---
lld/COFF/SymbolTable.cpp | 6 ++---
.../COFF/imports-static-lib-indirect.test | 26 +++++++++++++++++++
lld/test/COFF/imports-static-lib.test | 1 +
3 files changed, 30 insertions(+), 3 deletions(-)
create mode 100644 lld/test/COFF/imports-static-lib-indirect.test
diff --git a/lld/COFF/SymbolTable.cpp b/lld/COFF/SymbolTable.cpp
index d1fb6e05a0320..8fb0ee4e890d6 100644
--- a/lld/COFF/SymbolTable.cpp
+++ b/lld/COFF/SymbolTable.cpp
@@ -234,12 +234,12 @@ void SymbolTable::reportUndefinedSymbol(const UndefinedDiag &undefDiag) {
// Hints
StringRef name = undefDiag.sym->getName();
- if (name.starts_with("__imp_")) {
- Symbol *imp = find(name.substr(strlen("__imp_")));
+ if (name.consume_front("__imp_")) {
+ Symbol *imp = find(name);
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.";
+ << " but cannot be used because it is not an import library.";
}
}
}
diff --git a/lld/test/COFF/imports-static-lib-indirect.test b/lld/test/COFF/imports-static-lib-indirect.test
new file mode 100644
index 0000000000000..0ecb74a13de69
--- /dev/null
+++ b/lld/test/COFF/imports-static-lib-indirect.test
@@ -0,0 +1,26 @@
+# REQUIRES: x86
+
+# Pulling in on both a dllimport symbol and a static symbol should only warn.
+# RUN: split-file %s %t.dir
+# RUN: llvm-mc --filetype=obj -triple=x86_64-windows-msvc %t.dir/other.s -o %t.other.obj
+# RUN: llvm-mc --filetype=obj -triple=x86_64-windows-msvc %t.dir/main.s -o %t.main.obj
+# RUN: llvm-lib %t.other.obj -out:%t.other.lib
+# RUN: lld-link %t.other.lib %t.main.obj -out:%t.dll -dll 2>&1 | FileCheck %s
+
+CHECK: warning: {{.*}} [LNK4217]
+
+#--- other.s
+.text
+.globl other
+.globl foo
+other:
+ ret
+foo:
+ ret
+#--- main.s
+.text
+.global _DllMainCRTStartup
+_DllMainCRTStartup:
+ call *other(%rip)
+ call *__imp_foo(%rip)
+ ret
diff --git a/lld/test/COFF/imports-static-lib.test b/lld/test/COFF/imports-static-lib.test
index 63539cab9d860..8e9525dab5284 100644
--- a/lld/test/COFF/imports-static-lib.test
+++ b/lld/test/COFF/imports-static-lib.test
@@ -8,6 +8,7 @@
# 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
+CHECK: NOTE: a relevant symbol 'foo' is available in {{.*}}.foo.lib but cannot be used because it is not an import library.
# 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
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