[runtimes] Check if pragma comment(lib, ...) is supported first

This fixes the issue introduced by r362048 where we always use
pragma comment(lib, ...) for dependent libraries when the compiler
is Clang, but older Clang versions don't support this pragma so
we need to check first if it's supported before using it.

git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@362055 91177308-0d34-0410-b5e6-96231b3b80d8

CMakeLists.txt

@@ -552,6 +552,10 @@ if (NOT LIBCXX_ENABLE_NEW_DELETE_DEFINITIONS)
   add_definitions(-D_LIBCPP_DISABLE_NEW_DELETE_DEFINITIONS)
 endif()
 
+if (LIBCXX_HAS_COMMENT_LIB_PRAGMA)
+  add_definitions(-D_LIBCPP_HAS_COMMENT_LIB_PRAGMA)
+endif()
+
 # Warning flags ===============================================================
 add_definitions(-D_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
 add_compile_flags_if_supported(

cmake/config-ix.cmake

@@ -1,6 +1,7 @@
 include(CheckLibraryExists)
 include(CheckCCompilerFlag)
 include(CheckCXXCompilerFlag)
+include(CheckCSourceCompiles)
 
 if(WIN32 AND NOT MINGW)
   # NOTE(compnerd) this is technically a lie, there is msvcrt, but for now, lets
@@ -59,6 +60,14 @@ if (LIBCXX_SUPPORTS_NODEFAULTLIBS_FLAG)
   endif ()
 endif ()
 
+# Check compiler pragmas
+if(CMAKE_CXX_COMPILER_ID MATCHES "Clang")
+  check_c_source_compiles("
+#pragma comment(lib, \"c\")
+int main() { return 0; }
+" LIBCXX_HAS_COMMENT_LIB_PRAGMA)
+endif()
+
 if(NOT WIN32 OR MINGW)
   include(CheckLibcxxAtomic)
 endif()
@@ -72,7 +81,6 @@ check_cxx_compiler_flag(/EHs-                   LIBCXX_HAS_NO_EHS_FLAG)
 check_cxx_compiler_flag(/EHa-                   LIBCXX_HAS_NO_EHA_FLAG)
 check_cxx_compiler_flag(/GR-                    LIBCXX_HAS_NO_GR_FLAG)
 
-
 # Check libraries
 if(WIN32 AND NOT MINGW)
   # TODO(compnerd) do we want to support an emulation layer that allows for the

src/algorithm.cpp

@@ -10,7 +10,7 @@
 #include "random"
 #ifndef _LIBCPP_HAS_NO_THREADS
 #include "mutex"
-#if defined(__unix__) &&  defined(__ELF__) && defined(__clang__)
+#if defined(__unix__) &&  defined(__ELF__) && defined(_LIBCPP_HAS_COMMENT_LIB_PRAGMA)
 #pragma comment(lib, "pthread")
 #endif
 #endif

src/chrono.cpp

@@ -37,7 +37,7 @@
 #endif
 #endif
 
-#if defined(__unix__) &&  defined(__ELF__) && defined(__clang__)
+#if defined(__unix__) &&  defined(__ELF__) && defined(_LIBCPP_HAS_COMMENT_LIB_PRAGMA)
 #pragma comment(lib, "rt")
 #endif
 

src/debug.cpp

@@ -15,7 +15,7 @@
 #include "__hash_table"
 #ifndef _LIBCPP_HAS_NO_THREADS
 #include "mutex"
-#if defined(__unix__) &&  defined(__ELF__) && defined(__clang__)
+#if defined(__unix__) &&  defined(__ELF__) && defined(_LIBCPP_HAS_COMMENT_LIB_PRAGMA)
 #pragma comment(lib, "pthread")
 #endif
 #endif

src/experimental/memory_resource.cpp

@@ -12,7 +12,7 @@
 #include "atomic"
 #elif !defined(_LIBCPP_HAS_NO_THREADS)
 #include "mutex"
-#if defined(__unix__) &&  defined(__ELF__) && defined(__clang__)
+#if defined(__unix__) &&  defined(__ELF__) && defined(_LIBCPP_HAS_COMMENT_LIB_PRAGMA)
 #pragma comment(lib, "pthread")
 #endif
 #endif

src/filesystem/operations.cpp

@@ -44,7 +44,7 @@
 #include <sys/time.h> // for gettimeofday and timeval
 #endif                // !defined(CLOCK_REALTIME)
 
-#if defined(__unix__) &&  defined(__ELF__) && defined(__clang__)
+#if defined(__unix__) &&  defined(__ELF__) && defined(_LIBCPP_HAS_COMMENT_LIB_PRAGMA)
 #pragma comment(lib, "rt")
 #endif
 

src/mutex.cpp

@@ -13,7 +13,7 @@
 #include "__undef_macros"
 
 #ifndef _LIBCPP_HAS_NO_THREADS
-#if defined(__unix__) &&  defined(__ELF__) && defined(__clang__)
+#if defined(__unix__) &&  defined(__ELF__) && defined(_LIBCPP_HAS_COMMENT_LIB_PRAGMA)
 #pragma comment(lib, "pthread")
 #endif
 #endif

src/shared_mutex.cpp

@@ -10,7 +10,7 @@
 #ifndef _LIBCPP_HAS_NO_THREADS
 
 #include "shared_mutex"
-#if defined(__unix__) &&  defined(__ELF__) && defined(__clang__)
+#if defined(__unix__) &&  defined(__ELF__) && defined(_LIBCPP_HAS_COMMENT_LIB_PRAGMA)
 #pragma comment(lib, "pthread")
 #endif
 

src/thread.cpp

@@ -35,7 +35,7 @@
 #include <windows.h>
 #endif
 
-#if defined(__unix__) &&  defined(__ELF__) && defined(__clang__)
+#if defined(__unix__) &&  defined(__ELF__) && defined(_LIBCPP_HAS_COMMENT_LIB_PRAGMA)
 #pragma comment(lib, "pthread")
 #endif