[Clang][Cygwin] Enable few conditions that are shared with MinGW #149637

jeremyd2019 · 2025-07-19T05:52:38Z

The Cygwin target is generally very similar to the MinGW target. The default auto-import behavior, the default calling convention, the .dll.a import library extension, the __GXX_TYPEINFO_EQUALITY_INLINE pre-define by g++, and the long double configuration.

Co-authored-by: @mati865

Co-authored-by: Mateusz Mikuła <[email protected]>

llvmbot · 2025-07-19T05:53:08Z

@llvm/pr-subscribers-clang

Author: None (jeremyd2019)

Changes

The Cygwin target is generally very similar to the MinGW target

Co-authored-by: Mateusz Mikuła <[email protected]> (@mati865)

Full diff: https://github.com/llvm/llvm-project/pull/149637.diff

6 Files Affected:

(modified) clang/lib/AST/RecordLayoutBuilder.cpp (+1-1)
(modified) clang/lib/CIR/CodeGen/CIRGenModule.cpp (+4-4)
(modified) clang/lib/Driver/ToolChain.cpp (+1-1)
(modified) clang/lib/Driver/ToolChains/Clang.cpp (+1-1)
(modified) clang/lib/Frontend/InitPreprocessor.cpp (+2-2)
(modified) clang/lib/Sema/SemaDecl.cpp (+2-2)

diff --git a/clang/lib/AST/RecordLayoutBuilder.cpp b/clang/lib/AST/RecordLayoutBuilder.cpp
index 6a74e98dd92d8..760b2fcdc0681 100644
--- a/clang/lib/AST/RecordLayoutBuilder.cpp
+++ b/clang/lib/AST/RecordLayoutBuilder.cpp
@@ -1953,7 +1953,7 @@ void ItaniumRecordLayoutBuilder::LayoutField(const FieldDecl *D,
           // silently there. For other targets that have ms_struct enabled
           // (most probably via a pragma or attribute), trigger a diagnostic
           // that defaults to an error.
-          if (!Context.getTargetInfo().getTriple().isWindowsGNUEnvironment())
+          if (!Context.getTargetInfo().getTriple().isOSCygMing())
             Diag(D->getLocation(), diag::warn_npot_ms_struct);
         }
         if (TypeSize > FieldAlign &&
diff --git a/clang/lib/CIR/CodeGen/CIRGenModule.cpp b/clang/lib/CIR/CodeGen/CIRGenModule.cpp
index 350270518156e..5bc29b81c29a6 100644
--- a/clang/lib/CIR/CodeGen/CIRGenModule.cpp
+++ b/clang/lib/CIR/CodeGen/CIRGenModule.cpp
@@ -1530,10 +1530,10 @@ static bool shouldAssumeDSOLocal(const CIRGenModule &cgm,
 
   const llvm::Triple &tt = cgm.getTriple();
   const CodeGenOptions &cgOpts = cgm.getCodeGenOpts();
-  if (tt.isWindowsGNUEnvironment()) {
-    // In MinGW, variables without DLLImport can still be automatically
-    // imported from a DLL by the linker; don't mark variables that
-    // potentially could come from another DLL as DSO local.
+  if (tt.isOSCygMing()) {
+    // In MinGW and Cygwin, variables without DLLImport can still be
+    // automatically imported from a DLL by the linker; don't mark variables
+    // that potentially could come from another DLL as DSO local.
 
     // With EmulatedTLS, TLS variables can be autoimported from other DLLs
     // (and this actually happens in the public interface of libstdc++), so
diff --git a/clang/lib/Driver/ToolChain.cpp b/clang/lib/Driver/ToolChain.cpp
index 481f575518b93..7ef56856db8c7 100644
--- a/clang/lib/Driver/ToolChain.cpp
+++ b/clang/lib/Driver/ToolChain.cpp
@@ -773,7 +773,7 @@ std::string ToolChain::buildCompilerRTBasename(const llvm::opt::ArgList &Args,
     break;
   case ToolChain::FT_Shared:
     if (TT.isOSWindows())
-      Suffix = TT.isWindowsGNUEnvironment() ? ".dll.a" : ".lib";
+      Suffix = TT.isOSCygMing() ? ".dll.a" : ".lib";
     else if (TT.isOSAIX())
       Suffix = ".a";
     else
diff --git a/clang/lib/Driver/ToolChains/Clang.cpp b/clang/lib/Driver/ToolChains/Clang.cpp
index 8880c9375143f..8406d27dcf82a 100644
--- a/clang/lib/Driver/ToolChains/Clang.cpp
+++ b/clang/lib/Driver/ToolChains/Clang.cpp
@@ -5965,7 +5965,7 @@ void Clang::ConstructJob(Compilation &C, const JobAction &JA,
     CmdArgs.push_back("-mms-bitfields");
   }
 
-  if (Triple.isWindowsGNUEnvironment()) {
+  if (Triple.isOSCygMing()) {
     Args.addOptOutFlag(CmdArgs, options::OPT_fauto_import,
                        options::OPT_fno_auto_import);
   }
diff --git a/clang/lib/Frontend/InitPreprocessor.cpp b/clang/lib/Frontend/InitPreprocessor.cpp
index 382ccd610946c..008a35d5265e1 100644
--- a/clang/lib/Frontend/InitPreprocessor.cpp
+++ b/clang/lib/Frontend/InitPreprocessor.cpp
@@ -945,8 +945,8 @@ static void InitializePredefinedMacros(const TargetInfo &TI,
   if (LangOpts.GNUCVersion && LangOpts.CPlusPlus11)
     Builder.defineMacro("__GXX_EXPERIMENTAL_CXX0X__");
 
-  if (TI.getTriple().isWindowsGNUEnvironment()) {
-    // Set ABI defining macros for libstdc++ for MinGW, where the
+  if (TI.getTriple().isOSCygMing()) {
+    // Set ABI defining macros for libstdc++ for MinGW and Cygwin, where the
     // default in libstdc++ differs from the defaults for this target.
     Builder.defineMacro("__GXX_TYPEINFO_EQUALITY_INLINE", "0");
   }
diff --git a/clang/lib/Sema/SemaDecl.cpp b/clang/lib/Sema/SemaDecl.cpp
index 14403e65e8f42..a8878297a8220 100644
--- a/clang/lib/Sema/SemaDecl.cpp
+++ b/clang/lib/Sema/SemaDecl.cpp
@@ -12578,9 +12578,9 @@ static bool isDefaultStdCall(FunctionDecl *FD, Sema &S) {
   if (FD->getName() == "main" || FD->getName() == "wmain")
     return false;
 
-  // Default calling convention for MinGW is __cdecl
+  // Default calling convention for MinGW and Cygwin is __cdecl
   const llvm::Triple &T = S.Context.getTargetInfo().getTriple();
-  if (T.isWindowsGNUEnvironment())
+  if (T.isOSCygMing())
     return false;
 
   // Default calling convention for WinMain, wWinMain and DllMain

llvmbot · 2025-07-19T05:53:09Z

@llvm/pr-subscribers-clang-driver

Author: None (jeremyd2019)

Changes

The Cygwin target is generally very similar to the MinGW target

Co-authored-by: Mateusz Mikuła <[email protected]> (@mati865)

Full diff: https://github.com/llvm/llvm-project/pull/149637.diff

6 Files Affected:

(modified) clang/lib/AST/RecordLayoutBuilder.cpp (+1-1)
(modified) clang/lib/CIR/CodeGen/CIRGenModule.cpp (+4-4)
(modified) clang/lib/Driver/ToolChain.cpp (+1-1)
(modified) clang/lib/Driver/ToolChains/Clang.cpp (+1-1)
(modified) clang/lib/Frontend/InitPreprocessor.cpp (+2-2)
(modified) clang/lib/Sema/SemaDecl.cpp (+2-2)

diff --git a/clang/lib/AST/RecordLayoutBuilder.cpp b/clang/lib/AST/RecordLayoutBuilder.cpp
index 6a74e98dd92d8..760b2fcdc0681 100644
--- a/clang/lib/AST/RecordLayoutBuilder.cpp
+++ b/clang/lib/AST/RecordLayoutBuilder.cpp
@@ -1953,7 +1953,7 @@ void ItaniumRecordLayoutBuilder::LayoutField(const FieldDecl *D,
           // silently there. For other targets that have ms_struct enabled
           // (most probably via a pragma or attribute), trigger a diagnostic
           // that defaults to an error.
-          if (!Context.getTargetInfo().getTriple().isWindowsGNUEnvironment())
+          if (!Context.getTargetInfo().getTriple().isOSCygMing())
             Diag(D->getLocation(), diag::warn_npot_ms_struct);
         }
         if (TypeSize > FieldAlign &&
diff --git a/clang/lib/CIR/CodeGen/CIRGenModule.cpp b/clang/lib/CIR/CodeGen/CIRGenModule.cpp
index 350270518156e..5bc29b81c29a6 100644
--- a/clang/lib/CIR/CodeGen/CIRGenModule.cpp
+++ b/clang/lib/CIR/CodeGen/CIRGenModule.cpp
@@ -1530,10 +1530,10 @@ static bool shouldAssumeDSOLocal(const CIRGenModule &cgm,
 
   const llvm::Triple &tt = cgm.getTriple();
   const CodeGenOptions &cgOpts = cgm.getCodeGenOpts();
-  if (tt.isWindowsGNUEnvironment()) {
-    // In MinGW, variables without DLLImport can still be automatically
-    // imported from a DLL by the linker; don't mark variables that
-    // potentially could come from another DLL as DSO local.
+  if (tt.isOSCygMing()) {
+    // In MinGW and Cygwin, variables without DLLImport can still be
+    // automatically imported from a DLL by the linker; don't mark variables
+    // that potentially could come from another DLL as DSO local.
 
     // With EmulatedTLS, TLS variables can be autoimported from other DLLs
     // (and this actually happens in the public interface of libstdc++), so
diff --git a/clang/lib/Driver/ToolChain.cpp b/clang/lib/Driver/ToolChain.cpp
index 481f575518b93..7ef56856db8c7 100644
--- a/clang/lib/Driver/ToolChain.cpp
+++ b/clang/lib/Driver/ToolChain.cpp
@@ -773,7 +773,7 @@ std::string ToolChain::buildCompilerRTBasename(const llvm::opt::ArgList &Args,
     break;
   case ToolChain::FT_Shared:
     if (TT.isOSWindows())
-      Suffix = TT.isWindowsGNUEnvironment() ? ".dll.a" : ".lib";
+      Suffix = TT.isOSCygMing() ? ".dll.a" : ".lib";
     else if (TT.isOSAIX())
       Suffix = ".a";
     else
diff --git a/clang/lib/Driver/ToolChains/Clang.cpp b/clang/lib/Driver/ToolChains/Clang.cpp
index 8880c9375143f..8406d27dcf82a 100644
--- a/clang/lib/Driver/ToolChains/Clang.cpp
+++ b/clang/lib/Driver/ToolChains/Clang.cpp
@@ -5965,7 +5965,7 @@ void Clang::ConstructJob(Compilation &C, const JobAction &JA,
     CmdArgs.push_back("-mms-bitfields");
   }
 
-  if (Triple.isWindowsGNUEnvironment()) {
+  if (Triple.isOSCygMing()) {
     Args.addOptOutFlag(CmdArgs, options::OPT_fauto_import,
                        options::OPT_fno_auto_import);
   }
diff --git a/clang/lib/Frontend/InitPreprocessor.cpp b/clang/lib/Frontend/InitPreprocessor.cpp
index 382ccd610946c..008a35d5265e1 100644
--- a/clang/lib/Frontend/InitPreprocessor.cpp
+++ b/clang/lib/Frontend/InitPreprocessor.cpp
@@ -945,8 +945,8 @@ static void InitializePredefinedMacros(const TargetInfo &TI,
   if (LangOpts.GNUCVersion && LangOpts.CPlusPlus11)
     Builder.defineMacro("__GXX_EXPERIMENTAL_CXX0X__");
 
-  if (TI.getTriple().isWindowsGNUEnvironment()) {
-    // Set ABI defining macros for libstdc++ for MinGW, where the
+  if (TI.getTriple().isOSCygMing()) {
+    // Set ABI defining macros for libstdc++ for MinGW and Cygwin, where the
     // default in libstdc++ differs from the defaults for this target.
     Builder.defineMacro("__GXX_TYPEINFO_EQUALITY_INLINE", "0");
   }
diff --git a/clang/lib/Sema/SemaDecl.cpp b/clang/lib/Sema/SemaDecl.cpp
index 14403e65e8f42..a8878297a8220 100644
--- a/clang/lib/Sema/SemaDecl.cpp
+++ b/clang/lib/Sema/SemaDecl.cpp
@@ -12578,9 +12578,9 @@ static bool isDefaultStdCall(FunctionDecl *FD, Sema &S) {
   if (FD->getName() == "main" || FD->getName() == "wmain")
     return false;
 
-  // Default calling convention for MinGW is __cdecl
+  // Default calling convention for MinGW and Cygwin is __cdecl
   const llvm::Triple &T = S.Context.getTargetInfo().getTriple();
-  if (T.isWindowsGNUEnvironment())
+  if (T.isOSCygMing())
     return false;
 
   // Default calling convention for WinMain, wWinMain and DllMain

llvmbot · 2025-07-19T05:53:09Z

@llvm/pr-subscribers-clangir

Author: None (jeremyd2019)

Changes

The Cygwin target is generally very similar to the MinGW target

Co-authored-by: Mateusz Mikuła <[email protected]> (@mati865)

Full diff: https://github.com/llvm/llvm-project/pull/149637.diff

6 Files Affected:

(modified) clang/lib/AST/RecordLayoutBuilder.cpp (+1-1)
(modified) clang/lib/CIR/CodeGen/CIRGenModule.cpp (+4-4)
(modified) clang/lib/Driver/ToolChain.cpp (+1-1)
(modified) clang/lib/Driver/ToolChains/Clang.cpp (+1-1)
(modified) clang/lib/Frontend/InitPreprocessor.cpp (+2-2)
(modified) clang/lib/Sema/SemaDecl.cpp (+2-2)

diff --git a/clang/lib/AST/RecordLayoutBuilder.cpp b/clang/lib/AST/RecordLayoutBuilder.cpp
index 6a74e98dd92d8..760b2fcdc0681 100644
--- a/clang/lib/AST/RecordLayoutBuilder.cpp
+++ b/clang/lib/AST/RecordLayoutBuilder.cpp
@@ -1953,7 +1953,7 @@ void ItaniumRecordLayoutBuilder::LayoutField(const FieldDecl *D,
           // silently there. For other targets that have ms_struct enabled
           // (most probably via a pragma or attribute), trigger a diagnostic
           // that defaults to an error.
-          if (!Context.getTargetInfo().getTriple().isWindowsGNUEnvironment())
+          if (!Context.getTargetInfo().getTriple().isOSCygMing())
             Diag(D->getLocation(), diag::warn_npot_ms_struct);
         }
         if (TypeSize > FieldAlign &&
diff --git a/clang/lib/CIR/CodeGen/CIRGenModule.cpp b/clang/lib/CIR/CodeGen/CIRGenModule.cpp
index 350270518156e..5bc29b81c29a6 100644
--- a/clang/lib/CIR/CodeGen/CIRGenModule.cpp
+++ b/clang/lib/CIR/CodeGen/CIRGenModule.cpp
@@ -1530,10 +1530,10 @@ static bool shouldAssumeDSOLocal(const CIRGenModule &cgm,
 
   const llvm::Triple &tt = cgm.getTriple();
   const CodeGenOptions &cgOpts = cgm.getCodeGenOpts();
-  if (tt.isWindowsGNUEnvironment()) {
-    // In MinGW, variables without DLLImport can still be automatically
-    // imported from a DLL by the linker; don't mark variables that
-    // potentially could come from another DLL as DSO local.
+  if (tt.isOSCygMing()) {
+    // In MinGW and Cygwin, variables without DLLImport can still be
+    // automatically imported from a DLL by the linker; don't mark variables
+    // that potentially could come from another DLL as DSO local.
 
     // With EmulatedTLS, TLS variables can be autoimported from other DLLs
     // (and this actually happens in the public interface of libstdc++), so
diff --git a/clang/lib/Driver/ToolChain.cpp b/clang/lib/Driver/ToolChain.cpp
index 481f575518b93..7ef56856db8c7 100644
--- a/clang/lib/Driver/ToolChain.cpp
+++ b/clang/lib/Driver/ToolChain.cpp
@@ -773,7 +773,7 @@ std::string ToolChain::buildCompilerRTBasename(const llvm::opt::ArgList &Args,
     break;
   case ToolChain::FT_Shared:
     if (TT.isOSWindows())
-      Suffix = TT.isWindowsGNUEnvironment() ? ".dll.a" : ".lib";
+      Suffix = TT.isOSCygMing() ? ".dll.a" : ".lib";
     else if (TT.isOSAIX())
       Suffix = ".a";
     else
diff --git a/clang/lib/Driver/ToolChains/Clang.cpp b/clang/lib/Driver/ToolChains/Clang.cpp
index 8880c9375143f..8406d27dcf82a 100644
--- a/clang/lib/Driver/ToolChains/Clang.cpp
+++ b/clang/lib/Driver/ToolChains/Clang.cpp
@@ -5965,7 +5965,7 @@ void Clang::ConstructJob(Compilation &C, const JobAction &JA,
     CmdArgs.push_back("-mms-bitfields");
   }
 
-  if (Triple.isWindowsGNUEnvironment()) {
+  if (Triple.isOSCygMing()) {
     Args.addOptOutFlag(CmdArgs, options::OPT_fauto_import,
                        options::OPT_fno_auto_import);
   }
diff --git a/clang/lib/Frontend/InitPreprocessor.cpp b/clang/lib/Frontend/InitPreprocessor.cpp
index 382ccd610946c..008a35d5265e1 100644
--- a/clang/lib/Frontend/InitPreprocessor.cpp
+++ b/clang/lib/Frontend/InitPreprocessor.cpp
@@ -945,8 +945,8 @@ static void InitializePredefinedMacros(const TargetInfo &TI,
   if (LangOpts.GNUCVersion && LangOpts.CPlusPlus11)
     Builder.defineMacro("__GXX_EXPERIMENTAL_CXX0X__");
 
-  if (TI.getTriple().isWindowsGNUEnvironment()) {
-    // Set ABI defining macros for libstdc++ for MinGW, where the
+  if (TI.getTriple().isOSCygMing()) {
+    // Set ABI defining macros for libstdc++ for MinGW and Cygwin, where the
     // default in libstdc++ differs from the defaults for this target.
     Builder.defineMacro("__GXX_TYPEINFO_EQUALITY_INLINE", "0");
   }
diff --git a/clang/lib/Sema/SemaDecl.cpp b/clang/lib/Sema/SemaDecl.cpp
index 14403e65e8f42..a8878297a8220 100644
--- a/clang/lib/Sema/SemaDecl.cpp
+++ b/clang/lib/Sema/SemaDecl.cpp
@@ -12578,9 +12578,9 @@ static bool isDefaultStdCall(FunctionDecl *FD, Sema &S) {
   if (FD->getName() == "main" || FD->getName() == "wmain")
     return false;
 
-  // Default calling convention for MinGW is __cdecl
+  // Default calling convention for MinGW and Cygwin is __cdecl
   const llvm::Triple &T = S.Context.getTargetInfo().getTriple();
-  if (T.isWindowsGNUEnvironment())
+  if (T.isOSCygMing())
     return false;
 
   // Default calling convention for WinMain, wWinMain and DllMain

jeremyd2019 · 2025-07-19T06:15:38Z

@mati865 this is what was left of your patch, plus a couple more places I found grepping for WindowsGNU and considering whether the cases would also apply to Cygwin. I did back out the change you had to WinX86_64ABIInfo because that ABIInfo is not used on Cygwin (Cygwin has its own ABIInfo class)

mati865 · 2025-07-19T08:22:16Z

Thanks for taking care of it; I had thought these changes were already done by somebody.

mstorsjo

LGTM

mstorsjo · 2025-07-28T10:26:20Z

Also, if we could easily cover some of these cases with tests, that'd be nice.

I'd recommend rewriting the co-authored line in the PR description into something which isn't an @username reference, as that produces large amounts of notifications when the commit travels downstream into various repos - see https://discourse.llvm.org/t/forbidding-username-in-commits/86997.

jeremyd2019 · 2025-07-28T19:15:20Z

Yeah, the windres change needs some test adjustment as well I think.

jeremyd2019 · 2025-07-28T19:18:28Z

I'd recommend rewriting the co-authored line in the PR description into something which isn't an @username reference, as that produces large amounts of notifications when the commit travels downstream into various repos - see https://discourse.llvm.org/t/forbidding-username-in-commits/86997.

True. I don't much like putting email addresses in github comments/descriptions, so I changed it to the @username instead of the email address in the commit message. But given that the description turns into the commit message in squash merge, that may not be the best approach.

clang/lib/CIR/CodeGen/CIRGenModule.cpp

bcardosolopes

LGTM on the CIR side.

jeremyd2019 · 2025-07-28T23:45:36Z

I added tests for the ms-struct long double change and the __GXX_TYPEINFO_EQUALITY_INLINE preprocessor change, but I didn't see any CIR tests for windows or mingw behavior, and the .dll.a and auto-import changes would probably need #147960 before they could be tested

mstorsjo

LGTM

[Clang][Cygwin] Enable few conditions that are shared with MinGW

11621a5

Co-authored-by: Mateusz Mikuła <[email protected]>

jeremyd2019 requested a review from mstorsjo July 19, 2025 05:52

jeremyd2019 requested review from lanza, bcardosolopes, xlauko and andykaylor as code owners July 19, 2025 05:52

llvmbot added clang Clang issues not falling into any other category clang:driver 'clang' and 'clang++' user-facing binaries. Not 'clang-cl' clang:frontend Language frontend issues, e.g. anything involving "Sema" ClangIR Anything related to the ClangIR project labels Jul 19, 2025

mstorsjo approved these changes Jul 28, 2025

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bcardosolopes reviewed Jul 28, 2025

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bcardosolopes approved these changes Jul 28, 2025

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adjust tests

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[Clang][Cygwin] Enable few conditions that are shared with MinGW #149637

[Clang][Cygwin] Enable few conditions that are shared with MinGW #149637

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