[Driver] Disable static C++ library support on Fuchsia

[phosek]

Summary

Don't support or build static C++ libraries for Fuchsia.

[mcgrathr]

LGTM. The nit below is orthogonal to this change.

lib/Driver/ToolChains/Fuchsia.cpp

112 ↗

(On Diff #109255)

Shouldn't -lm be conditionalized on ShouldLinkCXXStdlib too?
It's only there to satisfy references from libc++, right?

OTOH, -lm is a no-op on Fuchsia so perhaps we should just drop it. On the third hand, we might separate libm from libc in the future so perhaps it's better to leave it.

[phosek]

lib/Driver/ToolChains/Fuchsia.cpp

112 ↗

(On Diff #109255)

I looked at all the other drivers and they all add -lm unconditionally, I'm not sure if it's just a copypasta or if there's some other reason behind it.

I also thought about removing it altogether but arrived to the same conclusion as you did.

cfe/trunk/cmake/caches/Fuchsia-stage2.cmake

 set(CMAKE_C_FLAGS_RELWITHDEBINFO "-O2 -gline-tables-only -DNDEBUG" CACHE STRING "")
 set(CMAKE_CXX_FLAGS_RELWITHDEBINFO "-O2 -gline-tables-only -DNDEBUG" CACHE STRING "")
 
 set(LLVM_BUILTIN_TARGETS "x86_64-fuchsia;aarch64-fuchsia" CACHE STRING "")
 foreach(target x86_64;aarch64)
   set(BUILTINS_${target}-fuchsia_CMAKE_SYSROOT ${FUCHSIA_${target}_SYSROOT} CACHE PATH "")
   set(BUILTINS_${target}-fuchsia_CMAKE_SYSTEM_NAME Fuchsia CACHE STRING "")
 endforeach()
+
 if(NOT APPLE)
   list(APPEND LLVM_BUILTIN_TARGETS "default")
 endif()
 
 set(LLVM_RUNTIME_TARGETS "default;x86_64-fuchsia;aarch64-fuchsia" CACHE STRING "")
 foreach(target x86_64;aarch64)
   set(RUNTIMES_${target}-fuchsia_CMAKE_BUILD_WITH_INSTALL_RPATH ON CACHE BOOL "")
   set(RUNTIMES_${target}-fuchsia_CMAKE_SYSROOT ${FUCHSIA_${target}_SYSROOT} CACHE PATH "")
   set(RUNTIMES_${target}-fuchsia_CMAKE_SYSTEM_NAME Fuchsia CACHE STRING "")
   set(RUNTIMES_${target}-fuchsia_UNIX 1 CACHE BOOL "")
   set(RUNTIMES_${target}-fuchsia_LLVM_ENABLE_LIBCXX ON CACHE BOOL "")
   set(RUNTIMES_${target}-fuchsia_LIBUNWIND_USE_COMPILER_RT ON CACHE BOOL "")
   set(RUNTIMES_${target}-fuchsia_LIBCXXABI_USE_COMPILER_RT ON CACHE BOOL "")
   set(RUNTIMES_${target}-fuchsia_LIBCXXABI_USE_LLVM_UNWINDER ON CACHE BOOL "")
+  set(RUNTIMES_${target}-fuchsia_LIBCXXABI_ENABLE_STATIC OFF CACHE BOOL "")
   set(RUNTIMES_${target}-fuchsia_LIBCXX_USE_COMPILER_RT ON CACHE BOOL "")
   set(RUNTIMES_${target}-fuchsia_LIBCXX_ABI_VERSION 2 CACHE STRING "")
+  set(RUNTIMES_${target}-fuchsia_LIBCXX_ENABLE_STATIC OFF CACHE BOOL "")
 endforeach()
 
 # Setup toolchain.
 set(LLVM_INSTALL_TOOLCHAIN_ONLY ON CACHE BOOL "")
 set(LLVM_TOOLCHAIN_TOOLS
   llc
   llvm-ar
   llvm-cov

cfe/trunk/lib/Driver/ToolChains/Fuchsia.cpp

void fuchsia::Linker::ConstructJob(Compilation &C, const JobAction &JA,
 
   AddLinkerInputs(ToolChain, Inputs, Args, CmdArgs, JA);
 
   if (!Args.hasArg(options::OPT_nostdlib, options::OPT_nodefaultlibs)) {
     if (Args.hasArg(options::OPT_static))
       CmdArgs.push_back("-Bdynamic");
 
     if (D.CCCIsCXX()) {
-      if (ToolChain.ShouldLinkCXXStdlib(Args)) {
-        bool OnlyLibstdcxxStatic = Args.hasArg(options::OPT_static_libstdcxx) &&
-                                   !Args.hasArg(options::OPT_static);
-        if (OnlyLibstdcxxStatic)
-          CmdArgs.push_back("-Bstatic");
+      if (ToolChain.ShouldLinkCXXStdlib(Args))
         ToolChain.AddCXXStdlibLibArgs(Args, CmdArgs);
-        if (OnlyLibstdcxxStatic)
-          CmdArgs.push_back("-Bdynamic");
-      }
       CmdArgs.push_back("-lm");
     }
 
     AddRunTimeLibs(ToolChain, D, CmdArgs, Args);
 
     if (Args.hasArg(options::OPT_pthread) ||
         Args.hasArg(options::OPT_pthreads))
       CmdArgs.push_back("-lpthread");

cfe/trunk/test/Driver/fuchsia.cpp

 // CHECK-NOT: crtn.o
 
 // RUN: %clangxx %s -### --target=x86_64-unknown-fuchsia -stdlib=libstdc++ 2>&1 \
 // RUN:     | FileCheck %s -check-prefix=CHECK-STDLIB
 // CHECK-STDLIB: error: invalid library name in argument '-stdlib=libstdc++'
 
 // RUN: %clangxx %s -### --target=x86_64-unknown-fuchsia -static-libstdc++ 2>&1 \
 // RUN:     | FileCheck %s -check-prefix=CHECK-STATIC
-// CHECK-STATIC: "-Bstatic"
+// CHECK-STATIC-NOT: "-Bstatic"
 // CHECK-STATIC: "-lc++" "-lc++abi" "-lunwind"
-// CHECK-STATIC: "-Bdynamic"
+// CHECK-STATIC-NOT: "-Bdynamic"
 // CHECK-STATIC: "-lm"
 // CHECK-STATIC: "-lc"