[cmake] Support enabling -Werror in the OpenMP runtime CMake build and clean up the build.

[chandlerc]

Summary

This disables all of the Clang warnings that fire for me when building
libomp.so on Linux with a recent Clang binary. Lots of these should
probably be fixed, but I want to at least get the build warning-clean
and make it easy to keep that way.

I also switched a bunch of the warnings that are used both for C and C++
compiles to check the flag with C compilation test.

[jlpeyton]

runtime/CMakeLists.txt

44

I think this should be FALSE. Even LLVM has it off by default. For example, on Linux building x86_64, gcc 4.8 warns that it might not be able to inline something that has an "always inline" attribute.

[chandlerc]

Good catch. Anything else? Not at a computer to update the patch but I will be later.

runtime/CMakeLists.txt

44

Of course, sorry. Will fix.

[jlpeyton]

Nope, that's the only thing. After that change, you can commit. Thanks for doing this! Jack Howarth and I had been doing work earlier to try and clean up some of these warnings, but I know there are still many to fix still. Now we can go through and clean up the warnings piecemeal by commenting out a -Wflag.

P.S. If anyone is wondering why we test for -Wflag and not -Wno-flag, it is because I saw gcc 4.8 and 4.9 accept '-Wno-this-cannot-be-a-flag' as a flag, but it did not accept '-Wthis-cannot-be-a-flag'.

[jlpeyton]

Officially accept after the one word fix.

runtime/CMakeLists.txt

if(${LIBOMP_STANDALONE_BUILD})
   set(LIBOMP_ARCH ${LIBOMP_DETECTED_ARCH} CACHE STRING
     "The architecture to build for (x86_64/i386/arm/ppc64/ppc64le/aarch64/mic).")
   # Allow user to choose a suffix for the installation directory.
   set(LIBOMP_LIBDIR_SUFFIX "" CACHE STRING
     "suffix of lib installation directory e.g., 64 => lib64")
   # Should assertions be enabled?  They are on by default.
   set(LIBOMP_ENABLE_ASSERTIONS TRUE CACHE BOOL
     "enable assertions?")
+  set(LIBOMP_ENABLE_WERROR TRUE CACHE BOOL
+    "Enable -Werror flags to turn warnings into errors for supporting compilers.")
   # CMAKE_BUILD_TYPE was not defined, set default to Release
   if(NOT CMAKE_BUILD_TYPE)
     set(CMAKE_BUILD_TYPE Release)
   endif()
 else() # Part of LLVM build
   # Determine the native architecture from LLVM.
   string(TOLOWER "${LLVM_TARGET_ARCH}" LIBOMP_NATIVE_ARCH)
   if( LIBOMP_NATIVE_ARCH STREQUAL "host" )
else() # Part of LLVM build
   elseif(LIBOMP_NATIVE_ARCH MATCHES "arm")
     set(LIBOMP_ARCH arm)
   else()
     # last ditch effort
     libomp_get_architecture(LIBOMP_ARCH)
   endif ()
   set(LIBOMP_LIBDIR_SUFFIX ${LLVM_LIBDIR_SUFFIX})
   set(LIBOMP_ENABLE_ASSERTIONS ${LLVM_ENABLE_ASSERTIONS})
+  set(LIBOMP_ENABLE_WERROR ${LLVM_ENABLE_WERROR})
 endif()
 libomp_check_variable(LIBOMP_ARCH 32e x86_64 32 i386 arm ppc64 ppc64le aarch64 mic)
 
 set(LIBOMP_LIB_TYPE normal CACHE STRING
   "Performance,Profiling,Stubs library (normal/profile/stubs)")
 libomp_check_variable(LIBOMP_LIB_TYPE normal profile stubs)
 set(LIBOMP_VERSION 5 CACHE STRING
   "Produce libguide (version 4) or libomp (version 5)")

runtime/cmake/LibompHandleFlags.cmake

macro(libomp_setup_flags flags)
   endif()
 endmacro()
 
 # Gets flags common to both the C and C++ compiler
 function(libomp_get_c_and_cxxflags_common flags)
   set(flags_local)
   libomp_append(flags_local -std=c++11 LIBOMP_HAVE_STD_CPP11_FLAG)
   libomp_append(flags_local -fno-exceptions LIBOMP_HAVE_FNO_EXCEPTIONS_FLAG)
-  libomp_append(flags_local -Wsign-compare LIBOMP_HAVE_WSIGN_COMPARE_FLAG)
+  if(${LIBOMP_ENABLE_WERROR})
+    libomp_append(flags_local -Werror LIBOMP_HAVE_WERROR_FLAG)
+  endif()
+  libomp_append(flags_local -Wno-sign-compare LIBOMP_HAVE_WNO_SIGN_COMPARE_FLAG)
+  libomp_append(flags_local -Wno-unused-function LIBOMP_HAVE_WNO_UNUSED_FUNCTION_FLAG)
+  libomp_append(flags_local -Wno-unused-local-typedef LIBOMP_HAVE_WNO_UNUSED_LOCAL_TYPEDEF_FLAG)
   libomp_append(flags_local -Wno-unused-value LIBOMP_HAVE_WNO_UNUSED_VALUE_FLAG)
+  libomp_append(flags_local -Wno-unused-variable LIBOMP_HAVE_WNO_UNUSED_VARIABLE_FLAG)
   libomp_append(flags_local -Wno-switch LIBOMP_HAVE_WNO_SWITCH_FLAG)
+  libomp_append(flags_local -Wno-covered-switch-default LIBOMP_HAVE_WNO_COVERED_SWITCH_DEFAULT_FLAG)
   libomp_append(flags_local -Wno-deprecated-register LIBOMP_HAVE_WNO_DEPRECATED_REGISTER_FLAG)
+  libomp_append(flags_local -Wno-gnu-anonymous-struct LIBOMP_HAVE_WNO_GNU_ANONYMOUS_STRUCT_FLAG)
+  libomp_append(flags_local -Wno-unknown-pragmas LIBOMP_HAVE_WNO_UNKNOWN_PRAGMAS_FLAG)
+  libomp_append(flags_local -Wno-missing-field-initializers LIBOMP_HAVE_WNO_MISSING_FIELD_INITIALIZERS_FLAG)
+  libomp_append(flags_local -Wno-missing-braces LIBOMP_HAVE_WNO_MISSING_BRACES_FLAG)
+  libomp_append(flags_local -Wno-comment LIBOMP_HAVE_WNO_COMMENT_FLAG)
+  libomp_append(flags_local -Wno-self-assign LIBOMP_HAVE_WNO_SELF_ASSIGN_FLAG)
+  libomp_append(flags_local -Wno-vla-extension LIBOMP_HAVE_WNO_VLA_EXTENSION_FLAG)
+  libomp_append(flags_local -Wno-format-pedantic LIBOMP_HAVE_WNO_FORMAT_PEDANTIC_FLAG)
   libomp_append(flags_local /GS LIBOMP_HAVE_GS_FLAG)
   libomp_append(flags_local /EHsc LIBOMP_HAVE_EHSC_FLAG)
   libomp_append(flags_local /Oy- LIBOMP_HAVE_OY__FLAG)
   # Intel(R) C Compiler flags
   libomp_append(flags_local /Qsafeseh LIBOMP_HAVE_QSAFESEH_FLAG)
   libomp_append(flags_local -Qoption,cpp,--extended_float_types LIBOMP_HAVE_EXTENDED_FLOAT_TYPES_FLAG)
   libomp_append(flags_local -Qlong_double LIBOMP_HAVE_LONG_DOUBLE_FLAG)
   libomp_append(flags_local -Qdiag-disable:177 LIBOMP_HAVE_DIAG_DISABLE_177_FLAG)

runtime/cmake/config-ix.cmake

function(libomp_check_architecture_flag flag retval)
   check_c_compiler_flag("${flag}" ${retval})
   set(${retval} ${${retval}} PARENT_SCOPE)
 endfunction()
 
 # Checking C, CXX, Linker Flags
 check_cxx_compiler_flag(-std=c++11 LIBOMP_HAVE_STD_CPP11_FLAG)
 check_cxx_compiler_flag(-fno-exceptions LIBOMP_HAVE_FNO_EXCEPTIONS_FLAG)
 check_c_compiler_flag("-x c++" LIBOMP_HAVE_X_CPP_FLAG)
-check_cxx_compiler_flag(-Wunused-value LIBOMP_HAVE_WNO_UNUSED_VALUE_FLAG)
-check_cxx_compiler_flag(-Wswitch LIBOMP_HAVE_WNO_SWITCH_FLAG)
-check_cxx_compiler_flag(-Wdeprecated-register LIBOMP_HAVE_WNO_DEPRECATED_REGISTER_FLAG)
-check_cxx_compiler_flag(-Wsign-compare LIBOMP_HAVE_WSIGN_COMPARE_FLAG)
-check_cxx_compiler_flag(-msse2 LIBOMP_HAVE_MSSE2_FLAG)
-check_cxx_compiler_flag(-ftls-model=initial-exec LIBOMP_HAVE_FTLS_MODEL_FLAG)
+check_c_compiler_flag(-Werror LIBOMP_HAVE_WERROR_FLAG)
+check_c_compiler_flag(-Wunused-function LIBOMP_HAVE_WNO_UNUSED_FUNCTION_FLAG)
+check_c_compiler_flag(-Wunused-local-typedef LIBOMP_HAVE_WNO_UNUSED_LOCAL_TYPEDEF_FLAG)
+check_c_compiler_flag(-Wunused-value LIBOMP_HAVE_WNO_UNUSED_VALUE_FLAG)
+check_c_compiler_flag(-Wunused-variable LIBOMP_HAVE_WNO_UNUSED_VARIABLE_FLAG)
+check_c_compiler_flag(-Wswitch LIBOMP_HAVE_WNO_SWITCH_FLAG)
+check_c_compiler_flag(-Wcovered-switch-default LIBOMP_HAVE_WNO_COVERED_SWITCH_DEFAULT_FLAG)
+check_c_compiler_flag(-Wdeprecated-register LIBOMP_HAVE_WNO_DEPRECATED_REGISTER_FLAG)
+check_c_compiler_flag(-Wsign-compare LIBOMP_HAVE_WNO_SIGN_COMPARE_FLAG)
+check_c_compiler_flag(-Wgnu-anonymous-struct LIBOMP_HAVE_WNO_GNU_ANONYMOUS_STRUCT_FLAG)
+check_c_compiler_flag(-Wunknown-pragmas LIBOMP_HAVE_WNO_UNKNOWN_PRAGMAS_FLAG)
+check_c_compiler_flag(-Wmissing-field-initializers LIBOMP_HAVE_WNO_MISSING_FIELD_INITIALIZERS_FLAG)
+check_c_compiler_flag(-Wmissing-braces LIBOMP_HAVE_WNO_MISSING_BRACES_FLAG)
+check_c_compiler_flag(-Wcomment LIBOMP_HAVE_WNO_COMMENT_FLAG)
+check_c_compiler_flag(-Wself-assign LIBOMP_HAVE_WNO_SELF_ASSIGN_FLAG)
+check_c_compiler_flag(-Wvla-extension LIBOMP_HAVE_WNO_VLA_EXTENSION_FLAG)
+check_c_compiler_flag(-Wformat-pedantic LIBOMP_HAVE_WNO_FORMAT_PEDANTIC_FLAG)
+check_c_compiler_flag(-msse2 LIBOMP_HAVE_MSSE2_FLAG)
+check_c_compiler_flag(-ftls-model=initial-exec LIBOMP_HAVE_FTLS_MODEL_FLAG)
 libomp_check_architecture_flag(-mmic LIBOMP_HAVE_MMIC_FLAG)
 libomp_check_architecture_flag(-m32 LIBOMP_HAVE_M32_FLAG)
 if(WIN32)
   # Check Windows MSVC style flags.
   check_c_compiler_flag(/TP LIBOMP_HAVE_TP_FLAG)
   check_cxx_compiler_flag(/EHsc LIBOMP_HAVE_EHSC_FLAG)
   check_cxx_compiler_flag(/GS LIBOMP_HAVE_GS_FLAG)
   check_cxx_compiler_flag(/Oy- LIBOMP_HAVE_Oy__FLAG)