Make a good guess about where MSVC and Windows SDK libraries are for linking.

When a user has not configured a standard Visual Studio environment
by running vcvarsall, clang tries its best to find Visual Studio
include files and executables anyway.  This patch makes clang also
try to find system and Windows SDK libraries for linking against,
as well.

Reviewed by: Hans Wennborg
Differential Revision: http://reviews.llvm.org/D5873

llvm-svn: 220425

3 files changed, 99 insertions, 0 deletions

diff --git a/clang/lib/Driver/MSVCToolChain.cpp b/clang/lib/Driver/MSVCToolChain.cpp
index 64708419270..a2f5e839848 100644
--- a/clang/lib/Driver/MSVCToolChain.cpp
+++ b/clang/lib/Driver/MSVCToolChain.cpp
@@ -212,6 +212,71 @@ bool MSVCToolChain::getWindowsSDKDir(std::string &path, int &major,
   return hasSDKDir && !path.empty();
 }
 
+// Gets the library path required to link against the Windows SDK.
+bool MSVCToolChain::getWindowsSDKLibraryPath(std::string &path) const {
+  std::string sdkPath;
+  int sdkMajor = 0;
+  int sdkMinor = 0;
+
+  path.clear();
+  if (!getWindowsSDKDir(sdkPath, sdkMajor, sdkMinor))
+    return false;
+
+  llvm::SmallString<128> libPath(sdkPath);
+  llvm::sys::path::append(libPath, "Lib");
+  if (sdkMajor <= 7) {
+    switch (getArch()) {
+    // In Windows SDK 7.x, x86 libraries are directly in the Lib folder.
+    case llvm::Triple::x86:
+      break;
+    case llvm::Triple::x86_64:
+      llvm::sys::path::append(libPath, "x64");
+      break;
+    case llvm::Triple::arm:
+      // It is not necessary to link against Windows SDK 7.x when targeting ARM.
+      return false;
+    default:
+      return false;
+    }
+  } else {
+    // Windows SDK 8.x installs libraries in a folder whose names depend on the
+    // version of the OS you're targeting.  By default choose the newest, which
+    // usually corresponds to the version of the OS you've installed the SDK on.
+    char *tests[] = {"winv6.3", "win8", "win7"};
+    bool found = false;
+    for (char *test : tests) {
+      llvm::SmallString<128> testPath(libPath);
+      llvm::sys::path::append(testPath, test);
+      if (llvm::sys::fs::exists(testPath.c_str())) {
+        libPath = testPath;
+        found = true;
+        break;
+      }
+    }
+
+    if (!found)
+      return false;
+
+    llvm::sys::path::append(libPath, "um");
+    switch (getArch()) {
+    case llvm::Triple::x86:
+      llvm::sys::path::append(libPath, "x86");
+      break;
+    case llvm::Triple::x86_64:
+      llvm::sys::path::append(libPath, "x64");
+      break;
+    case llvm::Triple::arm:
+      llvm::sys::path::append(libPath, "arm");
+      break;
+    default:
+      return false;
+    }
+  }
+
+  path = libPath.str();
+  return true;
+}
+
 // Get the location to use for Visual Studio binaries.  The location priority
 // is: %VCINSTALLDIR% > %PATH% > newest copy of Visual Studio installed on
 // system (as reported by the registry).
diff --git a/clang/lib/Driver/ToolChains.h b/clang/lib/Driver/ToolChains.h
index dbacccab0f3..525a7d29a4f 100644
--- a/clang/lib/Driver/ToolChains.h
+++ b/clang/lib/Driver/ToolChains.h
@@ -746,6 +746,7 @@ public:
                                llvm::opt::ArgStringList &CC1Args) const override;
 
   bool getWindowsSDKDir(std::string &path, int &major, int &minor) const;
+  bool getWindowsSDKLibraryPath(std::string &path) const;
   bool getVisualStudioInstallDir(std::string &path) const;
   bool getVisualStudioBinariesFolder(const char *clangProgramPath,
                                      std::string &path) const;
diff --git a/clang/lib/Driver/Tools.cpp b/clang/lib/Driver/Tools.cpp
index 1c0a6ff4a45..6e7060fedd0 100644
--- a/clang/lib/Driver/Tools.cpp
+++ b/clang/lib/Driver/Tools.cpp
@@ -7854,6 +7854,39 @@ void visualstudio::Link::ConstructJob(Compilation &C, const JobAction &JA,
     CmdArgs.push_back("-defaultlib:libcmt");
   }
 
+  if (!llvm::sys::Process::GetEnv("LIB")) {
+    // If the VC environment hasn't been configured (perhaps because the user
+    // did not run vcvarsall), try to build a consistent link environment.  If
+    // the environment variable is set however, assume the user knows what he's
+    // doing.
+    std::string VisualStudioDir;
+    const auto &MSVC = static_cast<const toolchains::MSVCToolChain &>(getToolChain());
+    if (MSVC.getVisualStudioInstallDir(VisualStudioDir)) {
+      SmallString<128> LibDir(VisualStudioDir);
+      llvm::sys::path::append(LibDir, "VC", "lib");
+      switch (MSVC.getArch()) {
+      case llvm::Triple::x86:
+        // x86 just puts the libraries directly in lib
+        break;
+      case llvm::Triple::x86_64:
+        llvm::sys::path::append(LibDir, "amd64");
+        break;
+      case llvm::Triple::arm:
+        llvm::sys::path::append(LibDir, "arm");
+        break;
+      default:
+        break;
+      }
+      CmdArgs.push_back(
+          Args.MakeArgString(std::string("-libpath:") + LibDir.c_str()));
+    }
+
+    std::string WindowsSdkLibPath;
+    if (MSVC.getWindowsSDKLibraryPath(WindowsSdkLibPath))
+      CmdArgs.push_back(Args.MakeArgString(std::string("-libpath:") +
+                                           WindowsSdkLibPath.c_str()));
+  }
+
   CmdArgs.push_back("-nologo");
 
   if (Args.hasArg(options::OPT_g_Group)) {