[libc] Set default CXX_STANDARD to C++17 and let targets set their own standard if needed.

[lntue]

Summary

CMAKE_CXX_STANDARD 14 is set in the llvm-project/llvm folder overriding all COMPILE_OPTIONS -std=c++17. We need to override the CXX_STANDARD property of the target in order to set the correct C++ standard flags.

[abrachet]

If you a need a c++17 compliant compiler to build libm, should we just set it for all of libc? Looks like flang already does this.

[lntue]

In D118871#3292655, @abrachet wrote:

If you a need a c++17 compliant compiler to build libm, should we just set it for all of libc? Looks like flang already does this.

In D118871#3292655, @abrachet wrote:

If you a need a c++17 compliant compiler to build libm, should we just set it for all of libc? Looks like flang already does this.

That sounds good to me if @sivachandra is fine with pushing the whole libc to C++17.

[lntue]

Set default CXX_STANDARD to C++17.

[gchatelet]

Thx! Wait for @sivachandra before submitting.

libc/CMakeLists.txt

 cmake_minimum_required(VERSION 3.13.4)
 
+# Default to C++17
+set(CMAKE_CXX_STANDARD 17)
+
 # Use old version of target_sources command which converts the source
 # file paths to full paths.
 cmake_policy(SET CMP0076 OLD)
 list(APPEND CMAKE_MODULE_PATH "${CMAKE_CURRENT_SOURCE_DIR}/cmake/modules")
 
 # The top-level sourse and binary directories.
 set(LIBC_SOURCE_DIR ${CMAKE_CURRENT_SOURCE_DIR})
 set(LIBC_BINARY_DIR ${CMAKE_CURRENT_BINARY_DIR})

libc/cmake/modules/LLVMLibCObjectRules.cmake

 #       <target_name>
 #       HDRS <list of header files>
 #       SRCS <list of source files>
 #       DEPENDS <list of dependencies>
 #       COMPILE_OPTIONS <optional list of special compile options for this target>
 function(add_object_library target_name)
   cmake_parse_arguments(
     "ADD_OBJECT"
-    "" # No option arguments
-    "" # Single value arguments
+    "" # No optional arguments
+    "CXX_STANDARD" # Single value arguments
     "SRCS;HDRS;COMPILE_OPTIONS;DEPENDS" # Multivalue arguments
     ${ARGN}
   )
 
   if(NOT ADD_OBJECT_SRCS)
     message(FATAL_ERROR "'add_object_library' rule requires SRCS to be specified.")
   endif()
 
function(add_object_library target_name)
   _get_common_compile_options(compile_options ${ADD_OBJECT_COMPILE_OPTIONS})
   target_compile_options(${fq_target_name} PRIVATE ${compile_options})
 
   get_fq_deps_list(fq_deps_list ${ADD_OBJECT_DEPENDS})
   if(fq_deps_list)
     add_dependencies(${fq_target_name} ${fq_deps_list})
   endif()
 
+  if(ADD_OBJECT_CXX_STANDARD)
+    set_target_properties(
+      ${fq_target_name}
+      PROPERTIES
+        CXX_STANDARD ${ADD_OBJECT_CXX_STANDARD}
+    )
+  endif()
+
   set_target_properties(
     ${fq_target_name}
     PROPERTIES
       "TARGET_TYPE" ${OBJECT_LIBRARY_TARGET_TYPE}
       "OBJECT_FILES" "$<TARGET_OBJECTS:${fq_target_name}>"
       "DEPS" "${fq_deps_list}"
   )
 endfunction(add_object_library)

 #       DEPENDS <list of dependencies>
 #       COMPILE_OPTIONS <optional list of special compile options for this target>
 #       SPECIAL_OBJECTS <optional list of special object targets added by the rule `add_object`>
 #     )
 function(add_entrypoint_object target_name)
   cmake_parse_arguments(
     "ADD_ENTRYPOINT_OBJ"
     "ALIAS;REDIRECTED" # Optional argument
-    "NAME" # Single value arguments
+    "NAME;CXX_STANDARD" # Single value arguments
     "SRCS;HDRS;DEPENDS;COMPILE_OPTIONS"  # Multi value arguments
     ${ARGN}
   )
 
   get_fq_target_name(${target_name} fq_target_name)
   set(entrypoint_name ${target_name})
   if(ADD_ENTRYPOINT_OBJ_NAME)
     set(entrypoint_name ${ADD_ENTRYPOINT_OBJ_NAME})
add_library(
     OBJECT
     ${ADD_ENTRYPOINT_OBJ_SRCS}
     ${ADD_ENTRYPOINT_OBJ_HDRS}
   )
   target_compile_options(${fq_target_name} BEFORE PRIVATE ${common_compile_options} -DLLVM_LIBC_PUBLIC_PACKAGING)
   target_include_directories(${fq_target_name} PRIVATE ${include_dirs})
   add_dependencies(${fq_target_name} ${full_deps_list})
 
+  if(ADD_ENTRYPOINT_OBJ_CXX_STANDARD)
+    set_target_properties(
+      ${fq_target_name} ${internal_target_name}
+      PROPERTIES
+        CXX_STANDARD ${ADD_ENTRYPOINT_OBJ_CXX_STANDARD}
+    )
+  endif()
+
   set_target_properties(
     ${fq_target_name}
     PROPERTIES
       "ENTRYPOINT_NAME" ${entrypoint_name}
       "TARGET_TYPE" ${ENTRYPOINT_OBJ_TARGET_TYPE}
       "OBJECT_FILE" $<TARGET_OBJECTS:${fq_target_name}>
       # TODO: We don't need to list internal object files if the internal
       # target is a normal static library.

libc/cmake/modules/LLVMLibCTestRules.cmake

 function(add_libc_unittest target_name)
   if(NOT LLVM_INCLUDE_TESTS)
     return()
   endif()
 
   cmake_parse_arguments(
     "LIBC_UNITTEST"
     "NO_RUN_POSTBUILD" # Optional arguments
-    "SUITE" # Single value arguments
+    "SUITE;CXX_STANDARD" # Single value arguments
     "SRCS;HDRS;DEPENDS;COMPILE_OPTIONS;LINK_OPTIONS" # Multi-value arguments
     "NO_LIBC_UNITTEST_TEST_MAIN"
     ${ARGN}
   )
   if(NOT LIBC_UNITTEST_SRCS)
     message(FATAL_ERROR "'add_libc_unittest' target requires a SRCS list of .cpp "
                         "files.")
   endif()
target_compile_options(
     PRIVATE ${LIBC_COMPILE_OPTIONS_DEFAULT}
   )
   if(LIBC_UNITTEST_COMPILE_OPTIONS)
     target_compile_options(
       ${fq_target_name}
       PRIVATE ${LIBC_UNITTEST_COMPILE_OPTIONS}
     )
   endif()
+  if(LIBC_UNITTEST_CXX_STANDARD)
+    set_target_properties(
+      ${fq_target_name}
+      PROPERTIES
+        CXX_STANDARD ${LIBC_UNITTEST_CXX_STANDARD}
+    )
+  endif()
 
   target_link_libraries(${fq_target_name} PRIVATE ${link_object_files})
   if(LIBC_UNITTEST_LINK_OPTIONS)
     target_link_options(
       ${fq_target_name}
       PRIVATE ${LIBC_UNITTEST_LINK_OPTIONS}
     )
   endif()

libc/src/math/generic/CMakeLists.txt

add_object_library(
   SRCS
     math_utils.cpp
   HDRS
     math_utils.h
   DEPENDS
     libc.include.errno
     libc.include.math
     libc.src.errno.__errno_location
-  COMPILE_OPTIONS
-    -Wno-c++17-extensions
 )
 
 add_object_library(
   sincosf_utils
   HDRS
     sincosf_utils.h
   SRCS
     sincosf_data.cpp
   DEPENDS
     .math_utils
-  COMPILE_OPTIONS
-    -Wno-c++17-extensions
 )
 
 add_entrypoint_object(
   cosf
   SRCS
     cosf.cpp
   HDRS
     ../cosf.h
   DEPENDS
     .sincosf_utils
     libc.include.math
     libc.src.errno.__errno_location
   COMPILE_OPTIONS
     -O3
-    -Wno-c++17-extensions
 )
 
 add_entrypoint_object(
   sinf
   SRCS
     sinf.cpp
   HDRS
     ../sinf.h
   DEPENDS
     .sincosf_utils
     libc.include.math
     libc.src.errno.__errno_location
     libc.src.__support.FPUtil.fputil
   COMPILE_OPTIONS
     -O3
-    -Wno-c++17-extensions
 )
 
 add_entrypoint_object(
   sincosf
   SRCS
     sincosf.cpp
   HDRS
     ../sincosf.h
   DEPENDS
     .sincosf_utils
     libc.include.math
     libc.src.errno.__errno_location
   COMPILE_OPTIONS
     -O3
-    -Wno-c++17-extensions
 )
 
 add_entrypoint_object(
   fabs
   SRCS
     fabs.cpp
   HDRS
     ../fabs.h

 )
 
 add_object_library(
   common_constants
   HDRS
     common_constants.h
   SRCS
     common_constants.cpp
-  COMPILE_OPTIONS
-    -Wno-c++17-extensions
 )
 
 add_entrypoint_object(
   log10f
   SRCS
     log10f.cpp
   HDRS
     ../log10f.h
   DEPENDS
     .common_constants
     libc.src.__support.FPUtil.fputil
   COMPILE_OPTIONS
     -O3
-    -Wno-c++17-extensions
 )
 
 add_entrypoint_object(
   log2f
   SRCS
     log2f.cpp
   HDRS
     ../log2f.h
   DEPENDS
     .common_constants
     libc.src.__support.FPUtil.fputil
     COMPILE_OPTIONS
     -O3
-    -Wno-c++17-extensions
 )
 
 add_entrypoint_object(
   logf
   SRCS
     logf.cpp
   HDRS
     ../logf.h
SRCS
     sqrt.cpp
   HDRS
     ../sqrt.h
   DEPENDS
     libc.src.__support.FPUtil.fputil
     libc.src.__support.FPUtil.sqrt
   COMPILE_OPTIONS
     -O3
-    -Wno-c++17-extensions
 )
 
 add_entrypoint_object(
   sqrtf
   SRCS
     sqrtf.cpp
   HDRS
     ../sqrtf.h
   DEPENDS
     libc.src.__support.FPUtil.fputil
     libc.src.__support.FPUtil.sqrt
   COMPILE_OPTIONS
     -O3
-    -Wno-c++17-extensions
 )
 
 add_entrypoint_object(
   sqrtl
   SRCS
     sqrtl.cpp
   HDRS
     ../sqrtl.h
   DEPENDS
     libc.src.__support.FPUtil.fputil
     libc.src.__support.FPUtil.sqrt
   COMPILE_OPTIONS
     -O3
-    -Wno-c++17-extensions
 )
 
 add_entrypoint_object(
   remquof
   SRCS
     remquof.cpp
   HDRS
     ../remquof.h

libc/src/math/generic/logf.cpp

 // Correctly Rounded Results of an Elementary Function for Multiple
 // Representations and Rounding Modes", Proceedings of the 49th ACM SIGPLAN
 // Symposium on Principles of Programming Languages (POPL-2022), Philadelphia,
 // USA, January 16-22, 2022.
 // https://people.cs.rutgers.edu/~sn349/papers/rlibmall-popl-2022.pdf
 
 namespace __llvm_libc {
 
-#pragma clang diagnostic push
-#pragma clang diagnostic ignored "-Wc++17-extensions"
-
 // Lookup table for log(f) = log(1 + n*2^(-7)) where n = 0..127.
 static constexpr double LOG_F[128] = {
     0x0.0000000000000p+0, 0x1.fe02a6b106788p-8, 0x1.fc0a8b0fc03e3p-7,
     0x1.7b91b07d5b11ap-6, 0x1.f829b0e783300p-6, 0x1.39e87b9febd5fp-5,
     0x1.77458f632dcfcp-5, 0x1.b42dd711971bep-5, 0x1.f0a30c01162a6p-5,
     0x1.16536eea37ae0p-4, 0x1.341d7961bd1d0p-4, 0x1.51b073f06183fp-4,
     0x1.6f0d28ae56b4bp-4, 0x1.8c345d6319b20p-4, 0x1.a926d3a4ad563p-4,
     0x1.c5e548f5bc743p-4, 0x1.e27076e2af2e5p-4, 0x1.fec9131dbeabap-4,
LLVM_LIBC_FUNCTION(float, logf, (float x)) {
 
   double r = __llvm_libc::fputil::polyeval(
       d, extra_factor, 0x1.fffffffffffacp-1, -0x1.fffffffef9cb2p-2,
       0x1.5555513bc679ap-2, -0x1.fff4805ea441p-3, 0x1.930180dbde91ap-3);
 
   return static_cast<float>(r);
 }
 
-#pragma clang diagnostic pop
-
 } // namespace __llvm_libc

libc/test/src/math/CMakeLists.txt

SUITE
     libc_math_unittests
   SRCS
     generic_sqrtf_test.cpp
   DEPENDS
     libc.src.__support.FPUtil.fputil
     libc.src.__support.FPUtil.generic.sqrt
   COMPILE_OPTIONS
     -O3
-    -Wno-c++17-extensions
 )
 
 add_fp_unittest(
   generic_sqrt_test
   NEED_MPFR
   SUITE
     libc_math_unittests
   SRCS
     generic_sqrt_test.cpp
   DEPENDS
     libc.src.__support.FPUtil.fputil
     libc.src.__support.FPUtil.generic.sqrt
   COMPILE_OPTIONS
     -O3
-    -Wno-c++17-extensions
 )
 
 add_fp_unittest(
   generic_sqrtl_test
   NEED_MPFR
   SUITE
     libc_math_unittests
   SRCS
     generic_sqrtl_test.cpp
   DEPENDS
     libc.src.__support.FPUtil.fputil
     libc.src.__support.FPUtil.generic.sqrt
   COMPILE_OPTIONS
     -O3
-    -Wno-c++17-extensions
 )
 
 add_fp_unittest(
   remquof_test
   NEED_MPFR
   SUITE
     libc_math_unittests
   SRCS
add_fp_unittest(
   SUITE
     libc_math_unittests
   SRCS
     hypotf_test.cpp
   DEPENDS
     libc.include.math
     libc.src.math.hypotf
     libc.src.__support.FPUtil.fputil
-  COMPILE_OPTIONS
-    -Wno-c++17-extensions
 )
 
 add_fp_unittest(
   hypot_test
   NEED_MPFR
   SUITE
     libc_math_unittests
   SRCS
     hypot_test.cpp
   DEPENDS
     libc.include.math
     libc.src.math.hypot
     libc.src.__support.FPUtil.fputil
-  COMPILE_OPTIONS
-    -Wno-c++17-extensions
 )
 
 add_fp_unittest(
   nextafter_test
   SUITE
     libc_math_unittests
   SRCS
     nextafter_test.cpp

libc/test/src/math/differential_testing/CMakeLists.txt

 
 function(add_diff_binary target_name)
   cmake_parse_arguments(
     "DIFF"
     "" # No optional arguments
-    "SUITE" # Single value arguments
+    "SUITE;CXX_STANDARD" # Single value arguments
     "SRCS;HDRS;DEPENDS;COMPILE_OPTIONS" # Multi-value arguments
     ${ARGN}
   )
   if(NOT DIFF_SRCS)
     message(FATAL_ERROR "'add_diff_binary' target requires a SRCS list of .cpp "
                         "files.")
   endif()
   if(NOT DIFF_DEPENDS)
function(add_diff_binary target_name)
   endif()
 
   target_link_libraries(
       ${fq_target_name}
       PRIVATE ${link_object_files} libc_test_utils)
 
   set_target_properties(${fq_target_name}
     PROPERTIES RUNTIME_OUTPUT_DIRECTORY ${CMAKE_CURRENT_BINARY_DIR})
   
+  if(DIFF_CXX_STANDARD)
+    set_target_properties(
+      ${fq_target_name}
+      PROPERTIES
+        CXX_STANDARD ${DIFF_CXX_STANDARD}
+    )
+  endif()
+
   add_dependencies(
     ${fq_target_name}
     libc.src.__support.FPUtil.fputil
     ${fq_deps_list}
   )
 endfunction()
 
 add_header_library(
add_diff_binary(
   hypotf_perf
   SRCS
     hypotf_perf.cpp
   DEPENDS
     .binary_op_single_output_diff
     libc.src.math.hypotf
   COMPILE_OPTIONS
     -fno-builtin
-    -Wno-c++17-extensions
 )
 
 add_diff_binary(
   hypot_perf
   SRCS
     hypot_perf.cpp
   DEPENDS
     .binary_op_single_output_diff
     libc.src.math.hypot
   COMPILE_OPTIONS
     -fno-builtin
-    -Wno-c++17-extensions
 )

libc/utils/MPFRWrapper/CMakeLists.txt

 if(LIBC_TESTS_CAN_USE_MPFR)
   add_library(libcMPFRWrapper
     MPFRUtils.cpp
     MPFRUtils.h
   )
+  add_compile_options(
+    -O3
+  )
   add_dependencies(libcMPFRWrapper libc.src.__support.CPP.standalone_cpp libc.src.__support.FPUtil.fputil LibcUnitTest)
   if(EXISTS ${LLVM_LIBC_MPFR_INSTALL_PATH})
     target_include_directories(libcMPFRWrapper PUBLIC ${LLVM_LIBC_MPFR_INSTALL_PATH}/include)
     target_link_directories(libcMPFRWrapper PUBLIC ${LLVM_LIBC_MPFR_INSTALL_PATH}/lib)
   endif()
   target_link_libraries(libcMPFRWrapper LibcFPTestHelpers LibcUnitTest mpfr gmp)
 else()
   message(WARNING "Math tests using MPFR will be skipped.")
 endif()