Add support in CMake to statically link the C++ standard library.

It is sometimes useful to have the C++ standard library linked into the
assembly when compiling clang, particularly when distributing a compiler
onto systems that don't have a copy of stdlibc++ or libc++ installed.

This functionality should work with either GCC or Clang as the host
compiler, though statically linking libc++ (as may be required for
licensing purposes) is only possible if the host compiler is Clang with
a copy of libc++ available.

Differential Revision: https://reviews.llvm.org/D65603

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@368907 91177308-0d34-0410-b5e6-96231b3b80d8

CMakeLists.txt

@@ -390,6 +390,7 @@ else()
   option(LLVM_ENABLE_LOCAL_SUBMODULE_VISIBILITY "Compile with -fmodules-local-submodule-visibility." ON)
 endif()
 option(LLVM_ENABLE_LIBCXX "Use libc++ if available." OFF)
+option(LLVM_STATIC_LINK_CXX_STDLIB "Statically link the standard library." OFF)
 option(LLVM_ENABLE_LLD "Use lld as C and C++ linker." OFF)
 option(LLVM_ENABLE_PEDANTIC "Compile with pedantic enabled." ON)
 option(LLVM_ENABLE_WERROR "Fail and stop if a warning is triggered." OFF)

cmake/modules/HandleLLVMStdlib.cmake

@@ -31,4 +31,24 @@ if(NOT DEFINED LLVM_STDLIB_HANDLED)
       message(WARNING "Not sure how to specify libc++ for this compiler")
     endif()
   endif()
+
+  if(LLVM_STATIC_LINK_CXX_STDLIB)
+    if(LLVM_COMPILER_IS_GCC_COMPATIBLE)
+      check_cxx_compiler_flag("-static-libstdc++"
+                              CXX_COMPILER_SUPPORTS_STATIC_STDLIB)
+      check_linker_flag("-static-libstdc++" CXX_LINKER_SUPPORTS_STATIC_STDLIB)
+      if(CXX_COMPILER_SUPPORTS_STATIC_STDLIB AND
+        CXX_LINKER_SUPPORTS_STATIC_STDLIB)
+        append("-static-libstdc++"
+          CMAKE_EXE_LINKER_FLAGS CMAKE_SHARED_LINKER_FLAGS
+          CMAKE_MODULE_LINKER_FLAGS)
+      else()
+        message(WARNING
+          "Can't specify static linking for the C++ standard library")
+      endif()
+    else()
+      message(WARNING "Not sure how to specify static linking of C++ standard "
+        "library for this compiler")
+    endif()
+  endif()
 endif()

docs/CMake.rst

@@ -431,6 +431,11 @@ LLVM-specific variables
   passed to invocations of both so that the project is built using libc++
   instead of stdlibc++. Defaults to OFF.
 
+**LLVM_STATIC_LINK_CXX_STDLIB**:BOOL
+  Statically link to the C++ standard library if possible. This uses the flag
+  "-static-libstdc++", but a Clang host compiler will statically link to libc++
+  if used in conjuction with the **LLVM_ENABLE_LIBCXX** flag. Defaults to OFF.
+
 **LLVM_ENABLE_LLD**:BOOL
   This option is equivalent to `-DLLVM_USE_LINKER=lld`, except during a 2-stage
   build where a dependency is added from the first stage to the second ensuring