[lld] [LLD][MinGW] Fix implicit DLL entry point (PR #171680)

via llvm-commits llvm-commits at lists.llvm.org
Wed Dec 10 12:52:17 PST 2025 

llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-lld-coff

Author: Mateusz MikuĊ‚a (mati865)

<details>
<summary>Changes</summary>

Previously LLD would always set 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 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.

Fixes https://github.com/llvm/llvm-project/issues/171441

---
Full diff: https://github.com/llvm/llvm-project/pull/171680.diff


12 Files Affected:

- (modified) lld/COFF/Driver.cpp (+9-2) 
- (modified) lld/test/COFF/autoimport-arm-code.s (+1-1) 
- (modified) lld/test/COFF/autoimport-arm-data.s (+1-1) 
- (modified) lld/test/COFF/autoimport-arm64-code.s (+1-1) 
- (modified) lld/test/COFF/autoimport-arm64-data.s (+1-1) 
- (modified) lld/test/COFF/autoimport-debug.s (+1-1) 
- (modified) lld/test/COFF/autoimport-gc.s (+1-1) 
- (modified) lld/test/COFF/autoimport-lto.ll (+1-1) 
- (modified) lld/test/COFF/autoimport-refptr.s (+1-1) 
- (modified) lld/test/COFF/autoimport-x86.s (+1-1) 
- (modified) lld/test/COFF/exclude-all.s (+2-2) 
- (modified) lld/test/COFF/export-all.s (+4-4) 


``````````diff
diff --git a/lld/COFF/Driver.cpp b/lld/COFF/Driver.cpp
index 0e528de9c3652..05679255703e9 100644
--- a/lld/COFF/Driver.cpp
+++ b/lld/COFF/Driver.cpp
@@ -1489,6 +1489,14 @@ getVFS(COFFLinkerContext &ctx, const opt::InputArgList &args) {
   return nullptr;
 }
 
+StringRef DllDefaultEntryPoint(MachineTypes machine, bool mingw) {
+  if (mingw) {
+    return (machine == I386) ? "_DllMainCRTStartup at 12" : "DllMainCRTStartup";
+  } else {
+    return (machine == I386) ? "__DllMainCRTStartup at 12" : "_DllMainCRTStartup";
+  }
+}
+
 constexpr const char *lldsaveTempsValues[] = {
     "resolution", "preopt",     "promote", "internalize",  "import",
     "opt",        "precodegen", "prelink", "combinedindex"};
@@ -2408,8 +2416,7 @@ 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 at 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
index 562a1a959e38b..8d7cc7f5cb019 100644
--- 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
index 82c66f0989d49..efc19f7f1865d 100644
--- 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
index 9f5cc8f894255..b7cddf9bac040 100644
--- 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
index 7934e2a969257..f3f16bc5210a4 100644
--- 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
index 1f31a2b9e554f..5865dac8d0d18 100644
--- 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
index fef6c02eba82f..f97fe4f534d27 100644
--- 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
index 94210e43cda6c..9a63d2f232d4e 100644
--- 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
index 4071d6be0809e..b087dd9363553 100644
--- 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
index 5d7c9c2c3fa58..39f2457a8259d 100644
--- 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
index f1977836b18cf..03dc0ddc6296e 100644
--- 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 at 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
index cd0a6f5f7b35a..70266f37809ca 100644
--- 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 at 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
 

``````````

</details>


https://github.com/llvm/llvm-project/pull/171680

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