Support for C11's _Thread_local was introduced in GCC in the 4.9 series,
even though we make the C11 compiler flags available in CMake with GCC
>= 4.6.
FreeBSD's runetype.h uses _Thread_local, which causes CMake's own build
to fail when using GCC < 4.9 and -std=gnu11:
/usr/include/runetype.h:92:22: error: expected '=', ',', ';', 'asm' or
'__attribute__' before 'const'
extern _Thread_local const _RuneLocale *_ThreadRuneLocale;
Add a test for _Thread_local support and only build CMake itself with
C11 support if it works.
Bug: http://www.cmake.org/Bug/view.php?id=15741
---
CMakeLists.txt | 7 ++-
Source/Checks/cm_c11_thread_local.c | 2 ++
Source/Checks/cm_c11_thread_local.cmake | 33 +
3 files changed, 41 insertions(+), 1 deletion(-)
create mode 100644 Source/Checks/cm_c11_thread_local.c
create mode 100644 Source/Checks/cm_c11_thread_local.cmake
diff --git a/CMakeLists.txt b/CMakeLists.txt
index 5e13a7e..94d138c 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -38,7 +38,12 @@ endif()
# Use most-recent available language dialects with GNU and Clang
if(NOT DEFINED CMAKE_C_STANDARD AND NOT CMake_NO_C_STANDARD)
- set(CMAKE_C_STANDARD 11)
+ include(${CMake_SOURCE_DIR}/Source/Checks/cm_c11_thread_local.cmake)
+ if(NOT CMake_C11_THREAD_LOCAL_BROKEN)
+set(CMAKE_C_STANDARD 11)
+ else()
+set(CMAKE_C_STANDARD 99)
+ endif()
endif()
if(NOT DEFINED CMAKE_CXX_STANDARD AND NOT CMake_NO_CXX_STANDARD)
include(${CMake_SOURCE_DIR}/Source/Checks/cm_cxx14_cstdio.cmake)
diff --git a/Source/Checks/cm_c11_thread_local.c
b/Source/Checks/cm_c11_thread_local.c
new file mode 100644
index 000..ab780f2
--- /dev/null
+++ b/Source/Checks/cm_c11_thread_local.c
@@ -0,0 +1,2 @@
+_Thread_local int i = 42;
+int main(void) { return 0; }
diff --git a/Source/Checks/cm_c11_thread_local.cmake
b/Source/Checks/cm_c11_thread_local.cmake
new file mode 100644
index 000..6b8d10b
--- /dev/null
+++ b/Source/Checks/cm_c11_thread_local.cmake
@@ -0,0 +1,33 @@
+set(CMake_C11_THREAD_LOCAL_BROKEN 0)
+if(CMAKE_CXX_COMPILER_ID MATCHES "GNU" AND CMAKE_C11_STANDARD_COMPILE_OPTION)
+ if(NOT DEFINED CMake_C11_THREAD_LOCAL_WORKS)
+message(STATUS "Checking if compiler supports C11 _Thread_local")
+try_compile(CMake_C11_THREAD_LOCAL_WORKS
+ ${CMAKE_CURRENT_BINARY_DIR}
+ ${CMAKE_CURRENT_LIST_DIR}/cm_c11_thread_local.c
+ CMAKE_FLAGS -DCMAKE_C_STANDARD=11
+ OUTPUT_VARIABLE OUTPUT
+ )
+if(CMake_C11_THREAD_LOCAL_WORKS AND "${OUTPUT}" MATCHES "error: expected
'=', ',', ';', 'asm' or '__attribute__' before 'int'")
+ set_property(CACHE CMake_C11_THREAD_LOCAL_WORKS PROPERTY VALUE 0)
+endif()
+if(CMake_C11_THREAD_LOCAL_WORKS)
+ message(STATUS "Checking if compiler supports C11 _Thread_local - yes")
+ file(APPEND ${CMAKE_BINARY_DIR}${CMAKE_FILES_DIRECTORY}/CMakeOutput.log
+"Determining if compiler supports C11 _Thread_local passed with the
following output:\n"
+"${OUTPUT}\n"
+"\n"
+)
+else()
+ message(STATUS "Checking if compiler supports C11 _Thread_local - no")
+ file(APPEND ${CMAKE_BINARY_DIR}${CMAKE_FILES_DIRECTORY}/CMakeError.log
+"Determining if compiler supports C11 _Thread_local failed with the
following output:\n"
+"${OUTPUT}\n"
+"\n"
+)
+endif()
+ endif()
+ if(NOT CMake_C11_THREAD_LOCAL_WORKS)
+set(CMake_C11_THREAD_LOCAL_BROKEN 1)
+ endif()
+endif()
--
2.5.2
--
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