For FreeBSD, use _p variants of libraries for linking C++ programs

[dim]

Summary

As reported in https://llvm.org/bugs/show_bug.cgi?id=25496, on FreeBSD,
C++ programs compiled for profiling (using -pg) should be linked with
-lc++_p (or -lstdc++_p, depending on the -stdlib= setting), not
with the regular C++ libraries.

Add a FreeBSD::AddCXXStdlibLibArgs() override to handle this, and add
a test case for it.

This review is intended to replace D16102.

[dws]

I will try this out on a system running FreeBSD HEAD (as of r294306) and see how it does.

[dim]

Ping.

[compnerd]

-p or -pg also effects the math library. Please adjust the tests and the driver to reflect that.

[dim]

In D16264#340131, @compnerd wrote:

-p or -pg also effects the math library. Please adjust the tests and the driver to reflect that.

This is already handled in lib/Driver/Tools.cpp, in freebsd::Linker::ConstructJob():

if (!Args.hasArg(options::OPT_nostdlib, options::OPT_nodefaultlibs)) {
  if (D.CCCIsCXX()) {
    getToolChain().AddCXXStdlibLibArgs(Args, CmdArgs);
    if (Args.hasArg(options::OPT_pg))
      CmdArgs.push_back("-lm_p");
    else
      CmdArgs.push_back("-lm");
  }

[compnerd]

I think it would be better if we could actually create a helper to get the profiling library name for a specific library, and use that in both locations.

Do we have a test for the math case at the very least?

[dim]

Add checks for -lm and -lm_p, when profiling is on.

lib/Driver/ToolChains.h

public:
 
   bool IsMathErrnoDefault() const override { return false; }
   bool IsObjCNonFragileABIDefault() const override { return true; }
 
   CXXStdlibType GetCXXStdlibType(const llvm::opt::ArgList &Args) const override;
   void AddClangCXXStdlibIncludeArgs(
       const llvm::opt::ArgList &DriverArgs,
       llvm::opt::ArgStringList &CC1Args) const override;
+  void AddCXXStdlibLibArgs(const llvm::opt::ArgList &Args,
+                           llvm::opt::ArgStringList &CmdArgs) const override;
 
   bool UseSjLjExceptions(const llvm::opt::ArgList &Args) const override;
   bool isPIEDefault() const override;
   SanitizerMask getSupportedSanitizers() const override;
   unsigned GetDefaultDwarfVersion() const override { return 2; }
   // Until dtrace (via CTF) and LLDB can deal with distributed debug info,
   // FreeBSD defaults to standalone/full debug info.
   bool GetDefaultStandaloneDebug() const override { return true; }

lib/Driver/ToolChains.cpp

case ToolChain::CST_Libstdcxx:
     addSystemInclude(DriverArgs, CC1Args,
                      getDriver().SysRoot + "/usr/include/c++/4.2");
     addSystemInclude(DriverArgs, CC1Args,
                      getDriver().SysRoot + "/usr/include/c++/4.2/backward");
     break;
   }
 }
 
+void FreeBSD::AddCXXStdlibLibArgs(const ArgList &Args,
+                                  ArgStringList &CmdArgs) const {
+  CXXStdlibType Type = GetCXXStdlibType(Args);
+  bool Profiling = Args.hasArg(options::OPT_pg);
+
+  switch (Type) {
+  case ToolChain::CST_Libcxx:
+    CmdArgs.push_back(Profiling ? "-lc++_p" : "-lc++");
+    break;
+
+  case ToolChain::CST_Libstdcxx:
+    CmdArgs.push_back(Profiling ? "-lstdc++_p" : "-lstdc++");
+    break;
+  }
+}
+
 Tool *FreeBSD::buildAssembler() const {
   return new tools::freebsd::Assembler(*this);
 }
 
 Tool *FreeBSD::buildLinker() const { return new tools::freebsd::Linker(*this); }
 
 bool FreeBSD::UseSjLjExceptions(const ArgList &Args) const {
   // FreeBSD uses SjLj exceptions on ARM oabi.

test/Driver/freebsd.cpp

 // RUN: %clangxx %s -### -o %t.o -target amd64-unknown-freebsd10.0 2>&1 \
 // RUN:   | FileCheck --check-prefix=CHECK-TEN %s
 // RUN: %clangxx %s -### -o %t.o -target amd64-unknown-freebsd9.2 2>&1 \
 // RUN:   | FileCheck --check-prefix=CHECK-NINE %s
-// CHECK-TEN: -lc++
-// CHECK-NINE: -lstdc++
+// CHECK-TEN: "-lc++" "-lm"
+// CHECK-NINE: "-lstdc++" "-lm"
+
+// RUN: %clangxx %s -### -pg -o %t.o -target amd64-unknown-freebsd10.0 2>&1 \
+// RUN:   | FileCheck --check-prefix=CHECK-PG-TEN %s
+// RUN: %clangxx %s -### -pg -o %t.o -target amd64-unknown-freebsd9.2 2>&1 \
+// RUN:   | FileCheck --check-prefix=CHECK-PG-NINE %s
+// CHECK-PG-TEN: "-lc++_p" "-lm_p"
+// CHECK-PG-NINE: "-lstdc++_p" "-lm_p"