[PATCH] D103771: [clang][msvc] Define _HAS_STATIC_RTTI to 0, when compiling with -fno-rtti

[Markus Böck via Phabricator via cfe-commits]

zero9178 created this revision.
zero9178 added reviewers: rnk, thakis, hans.
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When using the -fno-rtti option of the GCC style clang++, using typeid results in an error. The MSVC STL however kindly provides a define flag called _HAS_STATIC_RTTI, which either enables or disables uses of typeid throughout the STL. By default, if undefined, it is set to 1, enabling the use of typeid.

With this patch, _HAS_STATIC_RTTI is set to 0 when -fno-rtti is specified. This way various headers of the MSVC STL like functional can be consumed without compilation failures.

----

Some context: I was first made aware of this define in this bug report regarding twoPhase lookup: https://bugs.chromium.org/p/chromium/issues/detail?id=996675
Back then however there was still a usage of typeid left unguarded, which has since been fixed in this commit https://github.com/microsoft/STL/issues/340. 
Since that is November 2019, so a rather recent version of MSVC, this will not work in versions prior to this fix. 
For compat one could maybe allow `typeid(void)`, but that is beyond the scope of this patch either way I think.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D103771

Files:
  clang/lib/Driver/ToolChains/MSVC.cpp
  clang/lib/Driver/ToolChains/MSVC.h
  clang/test/Driver/msvc-static-rtti.cpp


Index: clang/test/Driver/msvc-static-rtti.cpp
===================================================================
--- /dev/null
+++ clang/test/Driver/msvc-static-rtti.cpp
@@ -0,0 +1,5 @@
+// RUN: %clang -target x86_64-pc-windows-msvc -fno-rtti -### %s 2>&1 | FileCheck %s -check-prefix STATIC-RTTI-DEF
+// RUN: %clang -target x86_64-pc-windows-msvc -frtti -### %s 2>&1 | FileCheck %s -check-prefix STATIC-RTTI-DEF-NOT
+
+// STATIC-RTTI-DEF: -D_HAS_STATIC_RTTI=0
+// STATIC-RTTI-DEF-NOT: -D_HAS_STATIC_RTTI=0
Index: clang/lib/Driver/ToolChains/MSVC.h
===================================================================
--- clang/lib/Driver/ToolChains/MSVC.h
+++ clang/lib/Driver/ToolChains/MSVC.h
@@ -122,6 +122,11 @@
 
   bool FoundMSVCInstall() const { return !VCToolChainPath.empty(); }
 
+  void
+  addClangTargetOptions(const llvm::opt::ArgList &DriverArgs,
+                        llvm::opt::ArgStringList &CC1Args,
+                        Action::OffloadKind DeviceOffloadKind) const override;
+
 protected:
   void AddSystemIncludeWithSubfolder(const llvm::opt::ArgList &DriverArgs,
                                      llvm::opt::ArgStringList &CC1Args,
Index: clang/lib/Driver/ToolChains/MSVC.cpp
===================================================================
--- clang/lib/Driver/ToolChains/MSVC.cpp
+++ clang/lib/Driver/ToolChains/MSVC.cpp
@@ -1555,3 +1555,11 @@
 
   return DAL;
 }
+
+void MSVCToolChain::addClangTargetOptions(
+    const ArgList &DriverArgs, ArgStringList &CC1Args,
+    Action::OffloadKind DeviceOffloadKind) const {
+  if (DriverArgs.hasArg(options::OPT_fno_rtti, options::OPT_frtti,
+                        /*Default=*/false))
+    CC1Args.push_back("-D_HAS_STATIC_RTTI=0");
+}


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