[PATCH] D51076: lld-link: Emit a warning if one of {main, wmain} and {WinMain, wWinMain} are both present and no explicit /subsystem: flag is passed.

[Nico Weber via Phabricator via llvm-commits]

thakis created this revision.
thakis added a reviewer: ruiu.

Similar to link.exe's LNK4031.


https://reviews.llvm.org/D51076

Files:
  COFF/Driver.cpp
  test/COFF/subsystem-inference2.test


Index: test/COFF/subsystem-inference2.test
===================================================================
--- test/COFF/subsystem-inference2.test
+++ test/COFF/subsystem-inference2.test
@@ -0,0 +1,54 @@
+# RUN: yaml2obj %s > %t.obj
+# RUN: lld-link /out:%t.exe %t.obj 2>&1 | FileCheck -check-prefix=WARN %s
+# RUN: llvm-readobj -file-headers %t.exe | FileCheck %s
+
+# WARN: warning: found main and WinMain; defaulting to /subsystem:console
+# CHECK:     Subsystem: IMAGE_SUBSYSTEM_WINDOWS_CUI
+
+--- !COFF
+header:
+  Machine:         IMAGE_FILE_MACHINE_AMD64
+  Characteristics: []
+sections:
+  - Name:            .text
+    Characteristics: [ IMAGE_SCN_CNT_CODE, IMAGE_SCN_MEM_EXECUTE, IMAGE_SCN_MEM_READ ]
+    Alignment:       4
+    SectionData:     B82A000000C3
+symbols:
+  - Name:            .text
+    Value:           0
+    SectionNumber:   1
+    SimpleType:      IMAGE_SYM_TYPE_NULL
+    ComplexType:     IMAGE_SYM_DTYPE_NULL
+    StorageClass:    IMAGE_SYM_CLASS_STATIC
+    SectionDefinition:
+      Length:          6
+      NumberOfRelocations: 0
+      NumberOfLinenumbers: 0
+      CheckSum:        0
+      Number:          0
+  - Name:            main
+    Value:           0
+    SectionNumber:   1
+    SimpleType:      IMAGE_SYM_TYPE_NULL
+    ComplexType:     IMAGE_SYM_DTYPE_NULL
+    StorageClass:    IMAGE_SYM_CLASS_EXTERNAL
+  - Name:            WinMain
+    Value:           0
+    SectionNumber:   1
+    SimpleType:      IMAGE_SYM_TYPE_NULL
+    ComplexType:     IMAGE_SYM_DTYPE_NULL
+    StorageClass:    IMAGE_SYM_CLASS_EXTERNAL
+  - Name:            mainCRTStartup
+    Value:           0
+    SectionNumber:   1
+    SimpleType:      IMAGE_SYM_TYPE_NULL
+    ComplexType:     IMAGE_SYM_DTYPE_NULL
+    StorageClass:    IMAGE_SYM_CLASS_EXTERNAL
+  - Name:            WinMainCRTStartup
+    Value:           0
+    SectionNumber:   1
+    SimpleType:      IMAGE_SYM_TYPE_NULL
+    ComplexType:     IMAGE_SYM_DTYPE_NULL
+    StorageClass:    IMAGE_SYM_CLASS_EXTERNAL
+...
Index: COFF/Driver.cpp
===================================================================
--- COFF/Driver.cpp
+++ COFF/Driver.cpp
@@ -449,9 +449,19 @@
 WindowsSubsystem LinkerDriver::inferSubsystem() {
   if (Config->DLL)
     return IMAGE_SUBSYSTEM_WINDOWS_GUI;
-  if (findUnderscoreMangle("main") || findUnderscoreMangle("wmain"))
+  bool HaveMain = findUnderscoreMangle("main");
+  bool HaveWMain = findUnderscoreMangle("wmain");
+  bool HaveWinMain = findUnderscoreMangle("WinMain");
+  bool HaveWWinMain = findUnderscoreMangle("wWinMain");
+  if (HaveMain || HaveWMain) {
+    if (HaveWinMain || HaveWWinMain) {
+      warn("found " + std::string(HaveMain ? "main" : "wmain") + " and " +
+           std::string(HaveWinMain ? "WinMain" : "wWinMain") +
+           "; defaulting to /subsystem:console");
+    }
     return IMAGE_SUBSYSTEM_WINDOWS_CUI;
-  if (findUnderscoreMangle("WinMain") || findUnderscoreMangle("wWinMain"))
+  }
+  if (HaveWinMain || HaveWWinMain)
     return IMAGE_SUBSYSTEM_WINDOWS_GUI;
   return IMAGE_SUBSYSTEM_UNKNOWN;
 }


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