Disable C++ EH by default for clang-cl and MSVC environments

We don't need any more bug reports from users telling us that MSVC-style
C++ exceptions are broken. Developers and adventurous users can still
test the existing functionality by passing along -fexceptions to either
clang or clang-cl.

llvm-svn: 241952

clang/include/clang/Driver/Options.td

@@ -506,7 +506,7 @@ def femit_all_decls : Flag<["-"], "femit-all-decls">, Group<f_Group>, Flags<[CC1
   HelpText<"Emit all declarations, even if unused">;
 def fencoding_EQ : Joined<["-"], "fencoding=">, Group<f_Group>;
 def ferror_limit_EQ : Joined<["-"], "ferror-limit=">, Group<f_Group>, Flags<[CoreOption]>;
-def fexceptions : Flag<["-"], "fexceptions">, Group<f_Group>, Flags<[CC1Option]>,
+def fexceptions : Flag<["-"], "fexceptions">, Group<f_Group>, Flags<[CC1Option, CoreOption]>,
   HelpText<"Enable support for exception handling">;
 def fexcess_precision_EQ : Joined<["-"], "fexcess-precision=">,
     Group<clang_ignored_gcc_optimization_f_Group>;

clang/lib/Driver/Tools.cpp

@@ -2041,17 +2041,6 @@ shouldUseExceptionTablesForObjCExceptions(const ObjCRuntime &runtime,
            Triple.getArch() == llvm::Triple::arm));
 }
 
-// exceptionSettings() exists to share the logic between -cc1 and linker
-// invocations.
-static bool exceptionSettings(const ArgList &Args, const llvm::Triple &Triple) {
-  if (Arg *A = Args.getLastArg(options::OPT_fexceptions,
-                               options::OPT_fno_exceptions))
-    if (A->getOption().matches(options::OPT_fexceptions))
-      return true;
-
-  return false;
-}
-
 /// Adds exception related arguments to the driver command arguments. There's a
 /// master flag, -fexceptions and also language specific flags to enable/disable
 /// C++ and Objective-C exceptions. This makes it possible to for example
@@ -2075,8 +2064,9 @@ static void addExceptionArgs(const ArgList &Args, types::ID InputType,
     return;
   }
 
-  // Gather the exception settings from the command line arguments.
-  bool EH = exceptionSettings(Args, Triple);
+  // See if the user explicitly enabled exceptions.
+  bool EH = Args.hasFlag(options::OPT_fexceptions, options::OPT_fno_exceptions,
+                         false);
 
   // Obj-C exceptions are enabled by default, regardless of -fexceptions. This
   // is not necessarily sensible, but follows GCC.
@@ -2089,8 +2079,11 @@ static void addExceptionArgs(const ArgList &Args, types::ID InputType,
   }
 
   if (types::isCXX(InputType)) {
-    bool CXXExceptionsEnabled =
-        Triple.getArch() != llvm::Triple::xcore && !Triple.isPS4CPU();
+    // Disable C++ EH by default on XCore, PS4, and MSVC.
+    // FIXME: Remove MSVC from this list once things work.
+    bool CXXExceptionsEnabled = Triple.getArch() != llvm::Triple::xcore &&
+                                !Triple.isPS4CPU() &&
+                                !Triple.isWindowsMSVCEnvironment();
     Arg *ExceptionArg = Args.getLastArg(
         options::OPT_fcxx_exceptions, options::OPT_fno_cxx_exceptions,
         options::OPT_fexceptions, options::OPT_fno_exceptions);
@@ -5040,6 +5033,7 @@ struct EHFlags {
 /// The default is /EHs-c-, meaning cleanups are disabled.
 static EHFlags parseClangCLEHFlags(const Driver &D, const ArgList &Args) {
   EHFlags EH;
+
   std::vector<std::string> EHArgs =
       Args.getAllArgValues(options::OPT__SLASH_EH);
   for (auto EHVal : EHArgs) {
@@ -5061,6 +5055,15 @@ static EHFlags parseClangCLEHFlags(const Driver &D, const ArgList &Args) {
       break;
     }
   }
+
+  // Only enable C++ exceptions if the user opts into it by passing
+  // -fexceptions. Lots of build systems implicitly pass /EHsc when users don't
+  // actually need it.
+  // FIXME: Remove this when they work out of the box.
+  if (!Args.hasFlag(options::OPT_fexceptions, options::OPT_fno_exceptions,
+                    /*default=*/false))
+    EH = EHFlags();
+
   return EH;
 }
 
@@ -9102,7 +9105,9 @@ void XCore::Linker::ConstructJob(Compilation &C, const JobAction &JA,
   if (Args.hasArg(options::OPT_v))
     CmdArgs.push_back("-v");
 
-  if (exceptionSettings(Args, getToolChain().getTriple()))
+  // Pass -fexceptions through to the linker if it was present.
+  if (Args.hasFlag(options::OPT_fexceptions, options::OPT_fno_exceptions,
+                   false))
     CmdArgs.push_back("-fexceptions");
 
   AddLinkerInputs(getToolChain(), Inputs, Args, CmdArgs);

clang/test/Driver/cl-eh.cpp

@@ -4,9 +4,13 @@
 // Note: %s must be preceded by --, otherwise it may be interpreted as a
 // command-line option, e.g. on Mac where %s is commonly under /Users.
 
+// RUN: %clang_cl /c /EHsc -fexceptions -### -- %s 2>&1 | FileCheck -check-prefix=EHscfex %s
+// EHscfex: "-fcxx-exceptions"
+// EHscfex: "-fexceptions"
+
 // RUN: %clang_cl /c /EHsc -### -- %s 2>&1 | FileCheck -check-prefix=EHsc %s
-// EHsc: "-fcxx-exceptions"
-// EHsc: "-fexceptions"
+// EHsc-NOT: "-fcxx-exceptions"
+// EHsc-NOT: "-fexceptions"
 
 // RUN: %clang_cl /c /EHs-c- -### -- %s 2>&1 | FileCheck -check-prefix=EHs_c_ %s
 // EHs_c_-NOT: "-fcxx-exceptions"
@@ -16,14 +20,14 @@
 // EHs_EHc_-NOT: "-fcxx-exceptions"
 // EHs_EHc_-NOT: "-fexceptions"
 
-// RUN: %clang_cl /c /EHs- /EHs -### -- %s 2>&1 | FileCheck -check-prefix=EHs_EHs %s
+// RUN: %clang_cl /c /EHs- /EHs -fexceptions -### -- %s 2>&1 | FileCheck -check-prefix=EHs_EHs %s
 // EHs_EHs: "-fcxx-exceptions"
 // EHs_EHs: "-fexceptions"
 
-// RUN: %clang_cl /c /EHs- /EHsa -### -- %s 2>&1 | FileCheck -check-prefix=EHs_EHa %s
+// RUN: %clang_cl /c /EHs- /EHsa -fexceptions -### -- %s 2>&1 | FileCheck -check-prefix=EHs_EHa %s
 // EHs_EHa: "-fcxx-exceptions"
 // EHs_EHa: "-fexceptions"
 
-// RUN: %clang_cl /c /EHinvalid -### -- %s 2>&1 | FileCheck -check-prefix=EHinvalid %s
+// RUN: %clang_cl /c /EHinvalid -fexceptions -### -- %s 2>&1 | FileCheck -check-prefix=EHinvalid %s
 // EHinvalid: error: invalid value 'invalid' in '/EH'
 // EHinvalid-NOT: error: