From e2afb47d1e3e7f5df4cc4ca5d295fa80e9abce48 Mon Sep 17 00:00:00 2001
From: David Majnemer <david.majnemer@gmail.com>
Date: Fri, 24 Jul 2015 06:49:13 +0000
Subject: [PATCH] [clang-cl] Implement support for the /Zl flag

The flag allows users to specify that they do not want the object file
to have any implicit /defaultlib directives.

This fixes PR24236.

llvm-svn: 243097
---
 clang/include/clang/Driver/CLCompatOptions.td |  3 ++-
 clang/lib/Driver/Tools.cpp                    | 23 ++++++++++++-------
 clang/test/Driver/cl-runtime-flags.c          |  9 ++++++++
 3 files changed, 26 insertions(+), 9 deletions(-)

diff --git a/clang/include/clang/Driver/CLCompatOptions.td b/clang/include/clang/Driver/CLCompatOptions.td
index 907b16fd5caf..ee148262ffe0 100644
--- a/clang/include/clang/Driver/CLCompatOptions.td
+++ b/clang/include/clang/Driver/CLCompatOptions.td
@@ -243,6 +243,8 @@ def _SLASH_vmv : CLFlag<"vmv">,
 def _SLASH_volatile_ms  : Option<["/", "-"], "volatile:ms", KIND_FLAG>,
   Group<_SLASH_volatile_Group>, Flags<[CLOption, DriverOption]>,
   HelpText<"Volatile loads and stores have acquire and release semantics">;
+def _SLASH_Zl : CLFlag<"Zl">,
+  HelpText<"Don't mention any default libraries in the object file">;
 
 // Ignored:
 
@@ -333,5 +335,4 @@ def _SLASH_Zc : CLJoined<"Zc:">;
 def _SLASH_Ze : CLFlag<"Ze">;
 def _SLASH_Zg : CLFlag<"Zg">;
 def _SLASH_ZI : CLFlag<"ZI">;
-def _SLASH_Zl : CLFlag<"Zl">;
 def _SLASH_ZW : CLJoined<"ZW">;
diff --git a/clang/lib/Driver/Tools.cpp b/clang/lib/Driver/Tools.cpp
index 6bab65a1115e..46a309fb830a 100644
--- a/clang/lib/Driver/Tools.cpp
+++ b/clang/lib/Driver/Tools.cpp
@@ -5098,39 +5098,46 @@ void Clang::AddClangCLArgs(const ArgList &Args, ArgStringList &CmdArgs) const {
   if (Arg *A = Args.getLastArg(options::OPT__SLASH_M_Group))
     RTOptionID = A->getOption().getID();
 
+  StringRef FlagForCRT;
   switch (RTOptionID) {
   case options::OPT__SLASH_MD:
     if (Args.hasArg(options::OPT__SLASH_LDd))
       CmdArgs.push_back("-D_DEBUG");
     CmdArgs.push_back("-D_MT");
     CmdArgs.push_back("-D_DLL");
-    CmdArgs.push_back("--dependent-lib=msvcrt");
+    FlagForCRT = "--dependent-lib=msvcrt";
     break;
   case options::OPT__SLASH_MDd:
     CmdArgs.push_back("-D_DEBUG");
     CmdArgs.push_back("-D_MT");
     CmdArgs.push_back("-D_DLL");
-    CmdArgs.push_back("--dependent-lib=msvcrtd");
+    FlagForCRT = "--dependent-lib=msvcrtd";
     break;
   case options::OPT__SLASH_MT:
     if (Args.hasArg(options::OPT__SLASH_LDd))
       CmdArgs.push_back("-D_DEBUG");
     CmdArgs.push_back("-D_MT");
-    CmdArgs.push_back("--dependent-lib=libcmt");
+    FlagForCRT = "--dependent-lib=libcmt";
     break;
   case options::OPT__SLASH_MTd:
     CmdArgs.push_back("-D_DEBUG");
     CmdArgs.push_back("-D_MT");
-    CmdArgs.push_back("--dependent-lib=libcmtd");
+    FlagForCRT = "--dependent-lib=libcmtd";
     break;
   default:
     llvm_unreachable("Unexpected option ID.");
   }
 
-  // This provides POSIX compatibility (maps 'open' to '_open'), which most
-  // users want.  The /Za flag to cl.exe turns this off, but it's not
-  // implemented in clang.
-  CmdArgs.push_back("--dependent-lib=oldnames");
+  if (Args.hasArg(options::OPT__SLASH_Zl)) {
+    CmdArgs.push_back("-D_VC_NODEFAULTLIB");
+  } else {
+    CmdArgs.push_back(FlagForCRT.data());
+
+    // This provides POSIX compatibility (maps 'open' to '_open'), which most
+    // users want.  The /Za flag to cl.exe turns this off, but it's not
+    // implemented in clang.
+    CmdArgs.push_back("--dependent-lib=oldnames");
+  }
 
   // Both /showIncludes and /E (and /EP) write to stdout. Allowing both
   // would produce interleaved output, so ignore /showIncludes in such cases.
diff --git a/clang/test/Driver/cl-runtime-flags.c b/clang/test/Driver/cl-runtime-flags.c
index de8f9d83d89d..a54aa1a14aee 100644
--- a/clang/test/Driver/cl-runtime-flags.c
+++ b/clang/test/Driver/cl-runtime-flags.c
@@ -84,3 +84,12 @@
 
 // RUN: %clang_cl /MD /MT -### -- %s 2>&1 | FileCheck -check-prefix=MTOVERRIDE %s
 // MTOVERRIDE: "--dependent-lib=libcmt"
+
+// RUN: %clang_cl -### /Zl -- %s 2>&1 | FileCheck -check-prefix=CHECK-MTZl %s
+// RUN: %clang_cl -### /MT /Zl -- %s 2>&1 | FileCheck -check-prefix=CHECK-MTZl %s
+// CHECK-MTZl-NOT: "-D_DEBUG"
+// CHECK-MTZl: "-D_MT"
+// CHECK-MTZl-NOT: "-D_DLL"
+// CHECK-MTZl-SAME: "-D_VC_NODEFAULTLIB"
+// CHECK-MTZl-NOT: "--dependent-lib=libcmt"
+// CHECK-MTZl-NOT: "--dependent-lib=oldnames"