[Darwin] Add a warning for missing include path for libstdc++

[arphaman]

Summary

Xcode 10 removes support for libstdc++, but the users just get a confusing include not file warning when including an STL header (when building for iOS6 which uses libstdc++ by default for example).
This patch adds a new warning that lets the user know that the libstdc++ include path was not found to ensure that the user is more aware of why the error occurs.

rdar://40830462

[bruno]

lib/Frontend/InitHeaderSearch.cpp

494

If we happen to suggest libc++, but it's also not there, do we still want the warning? Should we check it exists first?

[arphaman]

lib/Frontend/InitHeaderSearch.cpp

494

I don't think such a check is that valuable on Darwin, which is where this warning fires, since libc++ is the default standard library on Darwin.

[vsapsai]

lib/Frontend/InitHeaderSearch.cpp

374–380

Why are you using &= here instead of |=? I haven't tested but I expect that either 4.2.1 will work or 4.0.0, you don't need both of them.

404

What is so special about CUDA? Is it OK to emit the warning for OpenCL, for instance?

test/Frontend/warning-stdlibcxx-darwin.cpp

2–3

Do you think there is a value in adding a test that does exactly what the warning suggests and verifies there are no warnings?

[arphaman]

lib/Frontend/InitHeaderSearch.cpp

374–380

Good catch, fixed.

404

We're looking to warn for pure C++/ObjC++, so I will disable it for other language dialects.

test/Frontend/warning-stdlibcxx-darwin.cpp

2–3

Good call.

[arphaman]

Addressed review comments

[bruno]

LGTM

include/clang/Basic/DiagnosticFrontendKinds.td

 
 def err_missing_vfs_overlay_file : Error<
   "virtual filesystem overlay file '%0' not found">, DefaultFatal;
 def err_invalid_vfs_overlay : Error<
   "invalid virtual filesystem overlay file '%0'">, DefaultFatal;
 
 def warn_option_invalid_ocl_version : Warning<
   "OpenCL version %0 does not support the option '%1'">, InGroup<Deprecated>;
+
+def warn_stdlibcxx_not_found : Warning<
+  "include path for stdlibc++ headers not found; pass '-std=libc++' on the "
+  "command line to use the libc++ standard library instead">,
+  InGroup<DiagGroup<"stdlibcxx-not-found">>;
 }

include/clang/Lex/HeaderSearch.h

public:
   ~HeaderSearch();
 
   /// Retrieve the header-search options with which this header search
   /// was initialized.
   HeaderSearchOptions &getHeaderSearchOpts() const { return *HSOpts; }
   
   FileManager &getFileMgr() const { return FileMgr; }
 
+  DiagnosticsEngine &getDiags() const { return Diags; }
+
   /// Interface for setting the file search paths.
   void SetSearchPaths(const std::vector<DirectoryLookup> &dirs,
                       unsigned angledDirIdx, unsigned systemDirIdx,
                       bool noCurDirSearch) {
     assert(angledDirIdx <= systemDirIdx && systemDirIdx <= dirs.size() &&
         "Directory indices are unordered");
     SearchDirs = dirs;
     AngledDirIdx = angledDirIdx;

lib/Frontend/InitHeaderSearch.cpp

 //===--- InitHeaderSearch.cpp - Initialize header search paths ------------===//
 //
 //                     The LLVM Compiler Infrastructure
 //
 // This file is distributed under the University of Illinois Open Source
 // License. See LICENSE.TXT for details.
 //
 //===----------------------------------------------------------------------===//
 //
 // This file implements the InitHeaderSearch class.
 //
 //===----------------------------------------------------------------------===//
 
 #include "clang/Basic/FileManager.h"
 #include "clang/Basic/LangOptions.h"
 #include "clang/Config/config.h" // C_INCLUDE_DIRS
+#include "clang/Frontend/FrontendDiagnostic.h"
 #include "clang/Frontend/Utils.h"
 #include "clang/Lex/HeaderMap.h"
 #include "clang/Lex/HeaderSearch.h"
 #include "clang/Lex/HeaderSearchOptions.h"
 #include "llvm/ADT/SmallPtrSet.h"
 #include "llvm/ADT/SmallString.h"
 #include "llvm/ADT/SmallVector.h"
 #include "llvm/ADT/StringExtras.h"
public:
 
   InitHeaderSearch(HeaderSearch &HS, bool verbose, StringRef sysroot)
     : Headers(HS), Verbose(verbose), IncludeSysroot(sysroot),
       HasSysroot(!(sysroot.empty() || sysroot == "/")) {
   }
 
   /// AddPath - Add the specified path to the specified group list, prefixing
   /// the sysroot if used.
-  void AddPath(const Twine &Path, IncludeDirGroup Group, bool isFramework);
+  /// Returns true if the path exists, false if it was ignored.
+  bool AddPath(const Twine &Path, IncludeDirGroup Group, bool isFramework);
 
   /// AddUnmappedPath - Add the specified path to the specified group list,
   /// without performing any sysroot remapping.
-  void AddUnmappedPath(const Twine &Path, IncludeDirGroup Group,
+  /// Returns true if the path exists, false if it was ignored.
+  bool AddUnmappedPath(const Twine &Path, IncludeDirGroup Group,
                        bool isFramework);
 
   /// AddSystemHeaderPrefix - Add the specified prefix to the system header
   /// prefix list.
   void AddSystemHeaderPrefix(StringRef Prefix, bool IsSystemHeader) {
     SystemHeaderPrefixes.emplace_back(Prefix, IsSystemHeader);
   }
 
   /// AddGnuCPlusPlusIncludePaths - Add the necessary paths to support a gnu
   ///  libstdc++.
-  void AddGnuCPlusPlusIncludePaths(StringRef Base,
-                                   StringRef ArchDir,
-                                   StringRef Dir32,
-                                   StringRef Dir64,
+  /// Returns true if the \p Base path was found, false if it does not exist.
+  bool AddGnuCPlusPlusIncludePaths(StringRef Base, StringRef ArchDir,
+                                   StringRef Dir32, StringRef Dir64,
                                    const llvm::Triple &triple);
 
   /// AddMinGWCPlusPlusIncludePaths - Add the necessary paths to support a MinGW
   ///  libstdc++.
   void AddMinGWCPlusPlusIncludePaths(StringRef Base,
                                      StringRef Arch,
                                      StringRef Version);
 
   // AddDefaultCIncludePaths - Add paths that should always be searched.
   void AddDefaultCIncludePaths(const llvm::Triple &triple,
                                const HeaderSearchOptions &HSOpts);
 
   // AddDefaultCPlusPlusIncludePaths -  Add paths that should be searched when
   //  compiling c++.
-  void AddDefaultCPlusPlusIncludePaths(const llvm::Triple &triple,
+  void AddDefaultCPlusPlusIncludePaths(const LangOptions &LangOpts,
+                                       const llvm::Triple &triple,
                                        const HeaderSearchOptions &HSOpts);
 
   /// AddDefaultSystemIncludePaths - Adds the default system include paths so
   ///  that e.g. stdio.h is found.
   void AddDefaultIncludePaths(const LangOptions &Lang,
                               const llvm::Triple &triple,
                               const HeaderSearchOptions &HSOpts);
 
   /// Realize - Merges all search path lists into one list and send it to
   /// HeaderSearch.
   void Realize(const LangOptions &Lang);
 };
 
 }  // end anonymous namespace.
 
 static bool CanPrefixSysroot(StringRef Path) {
 #if defined(_WIN32)
   return !Path.empty() && llvm::sys::path::is_separator(Path[0]);
 #else
   return llvm::sys::path::is_absolute(Path);
 #endif
 }
 
-void InitHeaderSearch::AddPath(const Twine &Path, IncludeDirGroup Group,
+bool InitHeaderSearch::AddPath(const Twine &Path, IncludeDirGroup Group,
                                bool isFramework) {
   // Add the path with sysroot prepended, if desired and this is a system header
   // group.
   if (HasSysroot) {
     SmallString<256> MappedPathStorage;
     StringRef MappedPathStr = Path.toStringRef(MappedPathStorage);
     if (CanPrefixSysroot(MappedPathStr)) {
-      AddUnmappedPath(IncludeSysroot + Path, Group, isFramework);
-      return;
+      return AddUnmappedPath(IncludeSysroot + Path, Group, isFramework);
     }
   }
 
-  AddUnmappedPath(Path, Group, isFramework);
+  return AddUnmappedPath(Path, Group, isFramework);
 }
 
-void InitHeaderSearch::AddUnmappedPath(const Twine &Path, IncludeDirGroup Group,
+bool InitHeaderSearch::AddUnmappedPath(const Twine &Path, IncludeDirGroup Group,
                                        bool isFramework) {
   assert(!Path.isTriviallyEmpty() && "can't handle empty path here");
 
   FileManager &FM = Headers.getFileMgr();
   SmallString<256> MappedPathStorage;
   StringRef MappedPathStr = Path.toStringRef(MappedPathStorage);
 
   // Compute the DirectoryLookup type.
   SrcMgr::CharacteristicKind Type;
   if (Group == Quoted || Group == Angled || Group == IndexHeaderMap) {
     Type = SrcMgr::C_User;
   } else if (Group == ExternCSystem) {
     Type = SrcMgr::C_ExternCSystem;
   } else {
     Type = SrcMgr::C_System;
   }
 
   // If the directory exists, add it.
   if (const DirectoryEntry *DE = FM.getDirectory(MappedPathStr)) {
     IncludePath.push_back(
       std::make_pair(Group, DirectoryLookup(DE, Type, isFramework)));
-    return;
+    return true;
   }
 
   // Check to see if this is an apple-style headermap (which are not allowed to
   // be frameworks).
   if (!isFramework) {
     if (const FileEntry *FE = FM.getFile(MappedPathStr)) {
       if (const HeaderMap *HM = Headers.CreateHeaderMap(FE)) {
         // It is a headermap, add it to the search path.
         IncludePath.push_back(
           std::make_pair(Group,
                          DirectoryLookup(HM, Type, Group == IndexHeaderMap)));
-        return;
+        return true;
       }
     }
   }
 
   if (Verbose)
     llvm::errs() << "ignoring nonexistent directory \""
                  << MappedPathStr << "\"\n";
+  return false;
 }
 
-void InitHeaderSearch::AddGnuCPlusPlusIncludePaths(StringRef Base,
+bool InitHeaderSearch::AddGnuCPlusPlusIncludePaths(StringRef Base,
                                                    StringRef ArchDir,
                                                    StringRef Dir32,
                                                    StringRef Dir64,
                                                    const llvm::Triple &triple) {
   // Add the base dir
-  AddPath(Base, CXXSystem, false);
+  bool IsBaseFound = AddPath(Base, CXXSystem, false);
 
   // Add the multilib dirs
   llvm::Triple::ArchType arch = triple.getArch();
   bool is64bit = arch == llvm::Triple::ppc64 || arch == llvm::Triple::x86_64;
   if (is64bit)
     AddPath(Base + "/" + ArchDir + "/" + Dir64, CXXSystem, false);
   else
     AddPath(Base + "/" + ArchDir + "/" + Dir32, CXXSystem, false);
 
   // Add the backward dir
   AddPath(Base + "/backward", CXXSystem, false);
+  return IsBaseFound;
 }
 
 void InitHeaderSearch::AddMinGWCPlusPlusIncludePaths(StringRef Base,
                                                      StringRef Arch,
                                                      StringRef Version) {
   AddPath(Base + "/" + Arch + "/" + Version + "/include/c++",
           CXXSystem, false);
   AddPath(Base + "/" + Arch + "/" + Version + "/include/c++/" + Arch,
case llvm::Triple::PS4: {
     LLVM_FALLTHROUGH;
   }
   default:
     AddPath("/usr/include", ExternCSystem, false);
     break;
   }
 }
 
-void InitHeaderSearch::
-AddDefaultCPlusPlusIncludePaths(const llvm::Triple &triple, const HeaderSearchOptions &HSOpts) {
+void InitHeaderSearch::AddDefaultCPlusPlusIncludePaths(
+    const LangOptions &LangOpts, const llvm::Triple &triple,
+    const HeaderSearchOptions &HSOpts) {
   llvm::Triple::OSType os = triple.getOS();
   // FIXME: temporary hack: hard-coded paths.
 
   if (triple.isOSDarwin()) {
+    bool IsBaseFound = true;
     switch (triple.getArch()) {
     default: break;
 
     case llvm::Triple::ppc:
     case llvm::Triple::ppc64:
-      AddGnuCPlusPlusIncludePaths("/usr/include/c++/4.2.1",
-                                  "powerpc-apple-darwin10", "", "ppc64",
-                                  triple);
-      AddGnuCPlusPlusIncludePaths("/usr/include/c++/4.0.0",
-                                  "powerpc-apple-darwin10", "", "ppc64",
-                                  triple);
+      IsBaseFound = AddGnuCPlusPlusIncludePaths("/usr/include/c++/4.2.1",
+                                                "powerpc-apple-darwin10", "",
+                                                "ppc64", triple);
+      IsBaseFound |= AddGnuCPlusPlusIncludePaths("/usr/include/c++/4.0.0",
+                                                 "powerpc-apple-darwin10", "",
+                                                 "ppc64", triple);
       break;
 
     case llvm::Triple::x86:
     case llvm::Triple::x86_64:
-      AddGnuCPlusPlusIncludePaths("/usr/include/c++/4.2.1",
-                                  "i686-apple-darwin10", "", "x86_64", triple);
-      AddGnuCPlusPlusIncludePaths("/usr/include/c++/4.0.0",
-                                  "i686-apple-darwin8", "", "", triple);
+      IsBaseFound = AddGnuCPlusPlusIncludePaths("/usr/include/c++/4.2.1",
+                                                "i686-apple-darwin10", "",
+                                                "x86_64", triple);
+      IsBaseFound |= AddGnuCPlusPlusIncludePaths(
+          "/usr/include/c++/4.0.0", "i686-apple-darwin8", "", "", triple);
       break;
 
     case llvm::Triple::arm:
     case llvm::Triple::thumb:
-      AddGnuCPlusPlusIncludePaths("/usr/include/c++/4.2.1",
-                                  "arm-apple-darwin10", "v7", "", triple);
-      AddGnuCPlusPlusIncludePaths("/usr/include/c++/4.2.1",
-                                  "arm-apple-darwin10", "v6", "", triple);
+      IsBaseFound = AddGnuCPlusPlusIncludePaths(
+          "/usr/include/c++/4.2.1", "arm-apple-darwin10", "v7", "", triple);
+      IsBaseFound |= AddGnuCPlusPlusIncludePaths(
+          "/usr/include/c++/4.2.1", "arm-apple-darwin10", "v6", "", triple);
       break;
 
     case llvm::Triple::aarch64:
-      AddGnuCPlusPlusIncludePaths("/usr/include/c++/4.2.1",
-                                  "arm64-apple-darwin10", "", "", triple);
+      IsBaseFound = AddGnuCPlusPlusIncludePaths(
+          "/usr/include/c++/4.2.1", "arm64-apple-darwin10", "", "", triple);
       break;
     }
+    // Warn when compiling pure C++ / Objective-C++ only.
+    if (!IsBaseFound &&
+        !(LangOpts.CUDA || LangOpts.OpenCL || LangOpts.RenderScript)) {
+      Headers.getDiags().Report(SourceLocation(),
+                                diag::warn_stdlibcxx_not_found);
+    }
     return;
   }
 
   switch (os) {
   case llvm::Triple::Linux:
   case llvm::Triple::Solaris:
     llvm_unreachable("Include management is handled in the driver.");
     break;
if (HSOpts.UseLibcxx) {
 
           // Get foo/include/c++/v1
           llvm::sys::path::append(P, "include", "c++", "v1");
           AddUnmappedPath(P, CXXSystem, false);
         }
       }
       AddPath("/usr/include/c++/v1", CXXSystem, false);
     } else {
-      AddDefaultCPlusPlusIncludePaths(triple, HSOpts);
+      AddDefaultCPlusPlusIncludePaths(Lang, triple, HSOpts);
     }
   }
 
   AddDefaultCIncludePaths(triple, HSOpts);
 
   // Add the default framework include paths on Darwin.
   if (HSOpts.UseStandardSystemIncludes) {
     if (triple.isOSDarwin()) {

test/Frontend/warning-stdlibcxx-darwin.cpp

+// RUN: %clang -cc1 -triple arm64-apple-ios6.0.0 -isysroot %S/doesnotexist %s 2>&1 | FileCheck %s
+// RUN: %clang -cc1 -triple arm64-apple-ios6.0.0 -isysroot %S/doesnotexist -stdlib=libc++ %s -verify
+// CHECK: include path for stdlibc++ headers not found; pass '-std=libc++' on the command line to use the libc++ standard library instead
+
+// expected-no-diagnostics