From df7103ddc55577af52e9184922851673c52208c9 Mon Sep 17 00:00:00 2001
From: Artem Belevich <tra@google.com>
Date: Tue, 21 Jun 2016 19:34:40 +0000
Subject: [PATCH] [build] Make sure to link main executable with pthreads

Otherwise it gets linked in by one of the dependencies of shared
libraries which may be too late and we end up with weird crashes in
std::call_once().

Differential Revision: http://reviews.llvm.org/D21478

llvm-svn: 273302
---
 llvm/cmake/config-ix.cmake            |  8 +++++++-
 llvm/cmake/modules/AddLLVM.cmake      | 11 ++++++++++-
 llvm/tools/llvm-config/CMakeLists.txt |  8 +++++++-
 3 files changed, 24 insertions(+), 3 deletions(-)

diff --git a/llvm/cmake/config-ix.cmake b/llvm/cmake/config-ix.cmake
index 400ce32f835b..b363a357c581 100755
--- a/llvm/cmake/config-ix.cmake
+++ b/llvm/cmake/config-ix.cmake
@@ -110,7 +110,13 @@ if( NOT PURE_WINDOWS )
 endif()
 
 if(HAVE_LIBPTHREAD)
-  set(PTHREAD_LIB pthread)
+  # We want to find pthreads library and at the moment we do want to
+  # have it reported as '-l<lib>' instead of '-pthread'.
+  # TODO: switch to -pthread once the rest of the build system can deal with it.
+  set(CMAKE_THREAD_PREFER_PTHREAD TRUE)
+  set(THREADS_HAVE_PTHREAD_ARG Off)
+  find_package(Threads REQUIRED)
+  set(PTHREAD_LIB ${CMAKE_THREAD_LIBS_INIT})
 endif()
 
 # Don't look for these libraries on Windows. Also don't look for them if we're
diff --git a/llvm/cmake/modules/AddLLVM.cmake b/llvm/cmake/modules/AddLLVM.cmake
index 0f9d181216ff..ba507ddb56d2 100644
--- a/llvm/cmake/modules/AddLLVM.cmake
+++ b/llvm/cmake/modules/AddLLVM.cmake
@@ -670,6 +670,12 @@ macro(add_llvm_executable name)
   if(NOT ARG_IGNORE_EXTERNALIZE_DEBUGINFO)
     llvm_externalize_debuginfo(${name})
   endif()
+  if (PTHREAD_LIB)
+    # libpthreads overrides some standard library symbols, so main
+    # executable must be linked with it in order to provide consistent
+    # API for all shared libaries loaded by this executable.
+    target_link_libraries(${name} ${PTHREAD_LIB})
+  endif()
 endmacro(add_llvm_executable name)
 
 function(export_executable_symbols target)
@@ -953,7 +959,10 @@ function(add_unittest test_suite test_name)
   add_llvm_executable(${test_name} IGNORE_EXTERNALIZE_DEBUGINFO ${ARGN})
   set(outdir ${CMAKE_CURRENT_BINARY_DIR}/${CMAKE_CFG_INTDIR})
   set_output_directory(${test_name} BINARY_DIR ${outdir} LIBRARY_DIR ${outdir})
-  target_link_libraries(${test_name} gtest_main gtest)
+  # libpthreads overrides some standard library symbols, so main
+  # executable must be linked with it in order to provide consistent
+  # API for all shared libaries loaded by this executable.
+  target_link_libraries(${test_name} gtest_main gtest ${PTHREAD_LIB})
 
   add_dependencies(${test_suite} ${test_name})
   get_target_property(test_suite_folder ${test_suite} FOLDER)
diff --git a/llvm/tools/llvm-config/CMakeLists.txt b/llvm/tools/llvm-config/CMakeLists.txt
index 32d0f4c6bd6a..d45877135ba2 100644
--- a/llvm/tools/llvm-config/CMakeLists.txt
+++ b/llvm/tools/llvm-config/CMakeLists.txt
@@ -14,7 +14,13 @@ foreach(l ${LLVM_SYSTEM_LIBS_LIST})
   if(MSVC)
     set(SYSTEM_LIBS ${SYSTEM_LIBS} "${l}.lib")
   else()
-    set(SYSTEM_LIBS ${SYSTEM_LIBS} "-l${l}")
+    if (l MATCHES "^-")
+      # If it's an option, pass it without changes.
+      set(SYSTEM_LIBS ${SYSTEM_LIBS} "${l}")
+    else()
+      # Otherwise assume it's a library name we need to link with.
+      set(SYSTEM_LIBS ${SYSTEM_LIBS} "-l${l}")
+    endif()
   endif()
 endforeach()
 string(REPLACE ";" " " SYSTEM_LIBS "${SYSTEM_LIBS}")