[clang][Driver] Implement AddClangSystemIncludeArgs and HasNativeLLVMSupport for the OpenBSD clang driver.

If not overridden, AddClangSystemIncludeArgs's implementation is empty, so by
default, no system include args are added to the Clang driver. This means that
invoking Clang without the frontend must include a manual -I/usr/include flag,
which is inconsistent behavior. Therefore, override and implement this method
to match. Some boilerplate is also borrowed for handling of the other driver
flags.

While we are here, also override and enable HasNativeLLVMSupport.

Patch by: 3405691582 (dana koch)

Differential Revision: https://reviews.llvm.org/D86412

Author: brad0

clang/lib/Driver/ToolChains/OpenBSD.cpp

@@ -10,10 +10,12 @@
 #include "Arch/Mips.h"
 #include "Arch/Sparc.h"
 #include "CommonArgs.h"
+#include "clang/Config/config.h"
 #include "clang/Driver/Compilation.h"
 #include "clang/Driver/Options.h"
 #include "clang/Driver/SanitizerArgs.h"
 #include "llvm/Option/ArgList.h"
+#include "llvm/Support/Path.h"
 
 using namespace clang::driver;
 using namespace clang::driver::tools;
@@ -278,3 +280,38 @@ void OpenBSD::addClangTargetOptions(const ArgList &DriverArgs,
                           options::OPT_fno_use_init_array, false))
     CC1Args.push_back("-fno-use-init-array");
 }
+
+void OpenBSD::AddClangSystemIncludeArgs(
+    const llvm::opt::ArgList &DriverArgs,
+    llvm::opt::ArgStringList &CC1Args) const {
+  const Driver &D = getDriver();
+
+  if (DriverArgs.hasArg(clang::driver::options::OPT_nostdinc))
+    return;
+
+  if (!DriverArgs.hasArg(options::OPT_nobuiltininc)) {
+    SmallString<128> Dir(D.ResourceDir);
+    llvm::sys::path::append(Dir, "include");
+    addSystemInclude(DriverArgs, CC1Args, Dir.str());
+  }
+
+  if (DriverArgs.hasArg(options::OPT_nostdlibinc))
+    return;
+
+  // Check for configure-time C include directories.
+  StringRef CIncludeDirs(C_INCLUDE_DIRS);
+  if (CIncludeDirs != "") {
+    SmallVector<StringRef, 5> dirs;
+    CIncludeDirs.split(dirs, ":");
+    for (StringRef dir : dirs) {
+      StringRef Prefix =
+          llvm::sys::path::is_absolute(dir) ? StringRef(D.SysRoot) : "";
+      addExternCSystemInclude(DriverArgs, CC1Args, Prefix + dir);
+    }
+    return;
+  }
+
+  addExternCSystemInclude(DriverArgs, CC1Args, D.SysRoot + "/usr/include");
+}
+
+bool OpenBSD::HasNativeLLVMSupport() const { return true; }

clang/lib/Driver/ToolChains/OpenBSD.h

@@ -65,6 +65,12 @@ class LLVM_LIBRARY_VISIBILITY OpenBSD : public Generic_ELF {
     return ToolChain::CST_Libcxx;
   }
 
+  void
+  AddClangSystemIncludeArgs(const llvm::opt::ArgList &DriverArgs,
+                            llvm::opt::ArgStringList &CC1Args) const override;
+
+  bool HasNativeLLVMSupport() const override;
+
   void AddCXXStdlibLibArgs(const llvm::opt::ArgList &Args,
                            llvm::opt::ArgStringList &CmdArgs) const override;
 

clang/lib/Frontend/InitHeaderSearch.cpp

@@ -270,6 +270,7 @@ void InitHeaderSearch::AddDefaultCIncludePaths(const llvm::Triple &triple,
   case llvm::Triple::Linux:
   case llvm::Triple::Hurd:
   case llvm::Triple::Solaris:
+  case llvm::Triple::OpenBSD:
     llvm_unreachable("Include management is handled in the driver.");
 
   case llvm::Triple::CloudABI: {
@@ -423,6 +424,7 @@ void InitHeaderSearch::AddDefaultIncludePaths(const LangOptions &Lang,
   case llvm::Triple::Emscripten:
   case llvm::Triple::Linux:
   case llvm::Triple::Hurd:
+  case llvm::Triple::OpenBSD:
   case llvm::Triple::Solaris:
   case llvm::Triple::WASI:
   case llvm::Triple::AIX: