[LLD] [COFF] Fix implicit DLL entry point for MinGW (llvm#171680)

mati865 · mati865 · commit 00d23d10dc48 · 2025-12-18T14:08:00.000+01:00
Previously, LLD would always set the implicit entry point for DLLs to the symbol that is prefixed with an underscore. However, mingw-w64 defines it without that underscore. This change fixes that by adding a special branch for MinGW. Also, it simplifies tests that use MinGW style DLL entry symbol by skipping the entry point argument. Note, tests that use MSVC style DLL entry symbol and LLD in MinGW mode, will now require using explicit entry point. I believe this is sensible. When an explicit entry point is passed, i.e. LLD is called by Clang or GCC, there will be no observable difference. Fixes llvm#171441 (cherry picked from commit 2824225)
diff --git a/lld/COFF/Driver.cpp b/lld/COFF/Driver.cpp
@@ -1490,6 +1490,14 @@ getVFS(COFFLinkerContext &ctx, const opt::InputArgList &args) {
   return nullptr;
 }
 
+static StringRef DllDefaultEntryPoint(MachineTypes machine, bool mingw) {
+  if (mingw) {
+    return (machine == I386) ? "_DllMainCRTStartup@12" : "DllMainCRTStartup";
+  } else {
+    return (machine == I386) ? "__DllMainCRTStartup@12" : "_DllMainCRTStartup";
+  }
+}
+
 constexpr const char *lldsaveTempsValues[] = {
     "resolution", "preopt",     "promote", "internalize",  "import",
     "opt",        "precodegen", "prelink", "combinedindex"};
@@ -2378,8 +2386,7 @@ void LinkerDriver::linkerMain(ArrayRef<const char *> argsArr) {
       symtab.entry = symtab.addGCRoot(symtab.mangle(arg->getValue()), true);
     } else if (!symtab.entry && !config->noEntry) {
       if (args.hasArg(OPT_dll)) {
-        StringRef s = (config->machine == I386) ? "__DllMainCRTStartup@12"
-                                                : "_DllMainCRTStartup";
+        StringRef s = DllDefaultEntryPoint(config->machine, config->mingw);
         symtab.entry = symtab.addGCRoot(s, true);
       } else if (config->driverWdm) {
         // /driver:wdm implies /entry:_NtProcessStartup
diff --git a/lld/test/COFF/autoimport-arm-code.s b/lld/test/COFF/autoimport-arm-code.s
@@ -2,7 +2,7 @@
 
 # RUN: echo -e ".global variable\n.global DllMainCRTStartup\n.thumb\n.text\nDllMainCRTStartup:\nbx lr\n.data\nvariable:\n.long 42" > %t-lib.s
 # RUN: llvm-mc -triple=armv7-windows-gnu %t-lib.s -filetype=obj -o %t-lib.obj
-# RUN: lld-link -out:%t-lib.dll -dll -entry:DllMainCRTStartup %t-lib.obj -lldmingw -implib:%t-lib.lib
+# RUN: lld-link -out:%t-lib.dll -dll %t-lib.obj -lldmingw -implib:%t-lib.lib
 
 # RUN: llvm-mc -triple=armv7-windows-gnu %s -filetype=obj -o %t.obj
 # RUN: not lld-link -lldmingw -out:%t.exe -entry:main %t.obj %t-lib.lib 2>&1 | FileCheck %s
diff --git a/lld/test/COFF/autoimport-arm-data.s b/lld/test/COFF/autoimport-arm-data.s
@@ -2,7 +2,7 @@
 
 # RUN: echo -e ".global variable\n.global DllMainCRTStartup\n.thumb\n.text\nDllMainCRTStartup:\nbx lr\n.data\nvariable:\n.long 42" > %t-lib.s
 # RUN: llvm-mc -triple=armv7-windows-gnu %t-lib.s -filetype=obj -o %t-lib.obj
-# RUN: lld-link -out:%t-lib.dll -dll -entry:DllMainCRTStartup %t-lib.obj -lldmingw -implib:%t-lib.lib
+# RUN: lld-link -out:%t-lib.dll -dll %t-lib.obj -lldmingw -implib:%t-lib.lib
 
 # RUN: llvm-mc -triple=armv7-windows-gnu %s -filetype=obj -o %t.obj
 # RUN: lld-link -lldmingw -out:%t.exe -entry:main %t.obj %t-lib.lib -verbose
diff --git a/lld/test/COFF/autoimport-arm64-code.s b/lld/test/COFF/autoimport-arm64-code.s
@@ -2,7 +2,7 @@
 
 # RUN: echo -e ".global variable\n.global DllMainCRTStartup\n.text\nDllMainCRTStartup:\nret\n.data\nvariable:\n.long 42" > %t-lib.s
 # RUN: llvm-mc -triple=aarch64-windows-gnu %t-lib.s -filetype=obj -o %t-lib.obj
-# RUN: lld-link -out:%t-lib.dll -dll -entry:DllMainCRTStartup %t-lib.obj -lldmingw -implib:%t-lib.lib
+# RUN: lld-link -out:%t-lib.dll -dll %t-lib.obj -lldmingw -implib:%t-lib.lib
 
 # RUN: llvm-mc -triple=aarch64-windows-gnu %s -filetype=obj -o %t.obj
 # RUN: not lld-link -lldmingw -out:%t.exe -entry:main %t.obj %t-lib.lib 2>&1 | FileCheck %s
diff --git a/lld/test/COFF/autoimport-arm64-data.s b/lld/test/COFF/autoimport-arm64-data.s
@@ -2,7 +2,7 @@
 
 # RUN: echo -e ".global variable\n.global DllMainCRTStartup\n.text\nDllMainCRTStartup:\nret\n.data\nvariable:\n.long 42" > %t-lib.s
 # RUN: llvm-mc -triple=aarch64-windows-gnu %t-lib.s -filetype=obj -o %t-lib.obj
-# RUN: lld-link -out:%t-lib.dll -dll -entry:DllMainCRTStartup %t-lib.obj -lldmingw -implib:%t-lib.lib
+# RUN: lld-link -out:%t-lib.dll -dll %t-lib.obj -lldmingw -implib:%t-lib.lib
 
 # RUN: llvm-mc -triple=aarch64-windows-gnu %s -filetype=obj -o %t.obj
 # RUN: lld-link -lldmingw -out:%t.exe -entry:main %t.obj %t-lib.lib -verbose
diff --git a/lld/test/COFF/autoimport-debug.s b/lld/test/COFF/autoimport-debug.s
@@ -10,7 +10,7 @@
 ## debug info.
 
 # RUN: llvm-mc -triple=x86_64-windows-gnu %t.dir/lib.s -filetype=obj -o %t.dir/lib.obj
-# RUN: lld-link -out:%t.dir/lib.dll -dll -entry:DllMainCRTStartup %t.dir/lib.obj -lldmingw -implib:%t.dir/lib.lib
+# RUN: lld-link -out:%t.dir/lib.dll -dll %t.dir/lib.obj -lldmingw -implib:%t.dir/lib.lib
 
 # RUN: llvm-mc -triple=x86_64-windows-gnu %t.dir/main.s -filetype=obj -o %t.dir/main.obj
 # RUN: lld-link -lldmingw -out:%t.dir/main.exe -entry:main %t.dir/main.obj %t.dir/lib.lib -opt:noref -debug:dwarf -runtime-pseudo-reloc:no
diff --git a/lld/test/COFF/autoimport-gc.s b/lld/test/COFF/autoimport-gc.s
@@ -2,7 +2,7 @@
 # RUN: split-file %s %t.dir
 
 # RUN: llvm-mc -triple=x86_64-windows-gnu %t.dir/lib.s -filetype=obj -o %t.dir/lib.obj
-# RUN: lld-link -out:%t.dir/lib.dll -dll -entry:DllMainCRTStartup %t.dir/lib.obj -lldmingw -implib:%t.dir/lib.lib
+# RUN: lld-link -out:%t.dir/lib.dll -dll %t.dir/lib.obj -lldmingw -implib:%t.dir/lib.lib
 
 # RUN: llvm-mc -triple=x86_64-windows-gnu %t.dir/main.s -filetype=obj -o %t.dir/main.obj
 # RUN: lld-link -lldmingw -out:%t.dir/main.exe -entry:main %t.dir/main.obj %t.dir/lib.lib -opt:ref -debug:dwarf
diff --git a/lld/test/COFF/autoimport-lto.ll b/lld/test/COFF/autoimport-lto.ll
@@ -2,7 +2,7 @@
 
 ; RUN: echo -e ".global variable\n.global DllMainCRTStartup\n.text\nDllMainCRTStartup:\nret\n.data\nvariable:\n.long 42" > %t-lib.s
 ; RUN: llvm-mc -triple=x86_64-windows-gnu %t-lib.s -filetype=obj -o %t-lib.obj
-; RUN: lld-link -out:%t-lib.dll -dll -entry:DllMainCRTStartup %t-lib.obj -lldmingw -implib:%t-lib.lib
+; RUN: lld-link -out:%t-lib.dll -dll %t-lib.obj -lldmingw -implib:%t-lib.lib
 
 ; RUN: llvm-as -o %t.obj %s
 ; RUN: lld-link -lldmingw -out:%t.exe -entry:entry %t.obj %t-lib.lib
diff --git a/lld/test/COFF/autoimport-refptr.s b/lld/test/COFF/autoimport-refptr.s
@@ -2,7 +2,7 @@
 
 # RUN: echo -e ".global variable\n.global DllMainCRTStartup\n.text\nDllMainCRTStartup:\nret\n.data\nvariable:\n.long 42" > %t-lib.s
 # RUN: llvm-mc -triple=x86_64-windows-gnu %t-lib.s -filetype=obj -o %t-lib.obj
-# RUN: lld-link -out:%t-lib.dll -dll -entry:DllMainCRTStartup %t-lib.obj -lldmingw -implib:%t-lib.lib
+# RUN: lld-link -out:%t-lib.dll -dll %t-lib.obj -lldmingw -implib:%t-lib.lib
 
 # RUN: llvm-mc -triple=x86_64-windows-gnu %s -defsym listptrs=1 -filetype=obj -o %t.obj
 # RUN: lld-link -lldmingw -out:%t.exe -entry:main %t.obj %t-lib.lib -verbose
diff --git a/lld/test/COFF/autoimport-x86.s b/lld/test/COFF/autoimport-x86.s
@@ -2,7 +2,7 @@
 
 # RUN: echo -e ".global variable\n.global DllMainCRTStartup\n.text\nDllMainCRTStartup:\nret\n.data\nvariable:\n.long 42" > %t-lib.s
 # RUN: llvm-mc -triple=x86_64-windows-gnu %t-lib.s -filetype=obj -o %t-lib.obj
-# RUN: lld-link -out:%t-lib.dll -dll -entry:DllMainCRTStartup %t-lib.obj -lldmingw -implib:%t-lib.lib
+# RUN: lld-link -out:%t-lib.dll -dll %t-lib.obj -lldmingw -implib:%t-lib.lib
 
 # RUN: llvm-mc -triple=x86_64-windows-gnu -defsym listptrs=1 %s -filetype=obj -o %t.obj
 # RUN: lld-link -lldmingw -debug:symtab -out:%t.exe -entry:main %t.obj %t-lib.lib -verbose
diff --git a/lld/test/COFF/exclude-all.s b/lld/test/COFF/exclude-all.s
@@ -2,7 +2,7 @@
 
 # RUN: llvm-mc -triple=i686-windows-gnu %s -filetype=obj -o %t.obj
 
-# RUN: lld-link -lldmingw -exclude-all-symbols -dll -out:%t.dll -entry:DllMainCRTStartup@12 %t.obj
+# RUN: lld-link -lldmingw -exclude-all-symbols -dll -out:%t.dll %t.obj
 # RUN: llvm-readobj --coff-exports %t.dll | FileCheck %s -check-prefix=NO-EXPORTS
 
 # NO-EXPORTS-NOT: Name:
@@ -25,7 +25,7 @@ _dataSym:
 
 # RUN: yaml2obj %p/Inputs/export.yaml -o %t.obj
 #
-# RUN: lld-link -safeseh:no -out:%t.dll -dll %t.obj -lldmingw -exclude-all-symbols -output-def:%t.def
+# RUN: lld-link -safeseh:no -out:%t.dll -dll %t.obj -lldmingw -exclude-all-symbols -entry:_DllMainCRTStartup -output-def:%t.def
 # RUN: llvm-readobj --coff-exports %t.dll | FileCheck -check-prefix=DLLEXPORT %s
 
 # DLLEXPORT: Name: exportfn3
diff --git a/lld/test/COFF/export-all.s b/lld/test/COFF/export-all.s
@@ -2,7 +2,7 @@
 
 # RUN: llvm-mc -triple=i686-windows-gnu %s -filetype=obj -o %t.obj
 
-# RUN: lld-link -lldmingw -dll -out:%t.dll -entry:DllMainCRTStartup@12 %t.obj -implib:%t.lib
+# RUN: lld-link -lldmingw -dll -out:%t.dll %t.obj -implib:%t.lib
 # RUN: llvm-readobj --coff-exports %t.dll | grep Name: | FileCheck %s
 # RUN: llvm-readobj --coff-exports %t.dll | FileCheck %s --check-prefix=CHECK-RVA
 # RUN: llvm-readobj %t.lib | FileCheck -check-prefix=IMPLIB %s
@@ -57,7 +57,7 @@ __imp__unexported:
 
 # RUN: yaml2obj %p/Inputs/export.yaml -o %t.obj
 #
-# RUN: lld-link -safeseh:no -out:%t.dll -dll %t.obj -lldmingw -export-all-symbols -output-def:%t.def
+# RUN: lld-link -safeseh:no -out:%t.dll -dll %t.obj -lldmingw -export-all-symbols -entry:_DllMainCRTStartup -output-def:%t.def
 # RUN: llvm-readobj --coff-exports %t.dll | FileCheck -check-prefix=CHECK2 %s
 # RUN: cat %t.def | FileCheck -check-prefix=CHECK2-DEF %s
 
@@ -88,7 +88,7 @@ __imp__unexported:
 # RUN: llvm-ar rcs %t.dir/libs/libmingwex.a %t.dir/libs/mingwfunc.o
 # RUN: echo -e ".global crtfunc\n.text\ncrtfunc:\nret\n" > %t.dir/libs/crtfunc.s
 # RUN: llvm-mc -triple=x86_64-windows-gnu %t.dir/libs/crtfunc.s -filetype=obj -o %t.dir/libs/crt2.o
-# RUN: lld-link -safeseh:no -out:%t.dll -dll -entry:DllMainCRTStartup %t.main.obj -lldmingw %t.dir/libs/crt2.o %t.dir/libs/libmingwex.a -output-def:%t.def
+# RUN: lld-link -safeseh:no -out:%t.dll -dll %t.main.obj -lldmingw %t.dir/libs/crt2.o %t.dir/libs/libmingwex.a -output-def:%t.def
 # RUN: echo "EOF" >> %t.def
 # RUN: cat %t.def | FileCheck -check-prefix=CHECK-EXCLUDE %s
 
@@ -99,7 +99,7 @@ __imp__unexported:
 # Test that libraries included with -wholearchive: are autoexported, even if
 # they are in a library that otherwise normally would be excluded.
 
-# RUN: lld-link -safeseh:no -out:%t.dll -dll -entry:DllMainCRTStartup %t.main.obj -lldmingw %t.dir/libs/crt2.o -wholearchive:%t.dir/libs/libmingwex.a -output-def:%t.def
+# RUN: lld-link -safeseh:no -out:%t.dll -dll %t.main.obj -lldmingw %t.dir/libs/crt2.o -wholearchive:%t.dir/libs/libmingwex.a -output-def:%t.def
 # RUN: echo "EOF" >> %t.def
 # RUN: cat %t.def | FileCheck -check-prefix=CHECK-WHOLEARCHIVE %s
 
