cleanup: remove pre-CMake 3.8 workarounds

Since Abseil requires CMake >= 3.10, we can remove some workarounds.

PiperOrigin-RevId: 511856584
Change-Id: I0385fa87b51147b69df7e2dd18b317cf6cde83c2

CMake/AbseilDll.cmake

@@ -594,14 +594,6 @@ set(ABSL_INTERNAL_TEST_DLL_TARGETS
   "scoped_mock_log"
 )
 
-function(_absl_target_compile_features_if_available TARGET TYPE FEATURE)
-  if(FEATURE IN_LIST CMAKE_CXX_COMPILE_FEATURES)
-    target_compile_features(${TARGET} ${TYPE} ${FEATURE})
-  else()
-    message(WARNING "Feature ${FEATURE} is unknown for the CXX compiler")
-  endif()
-endfunction()
-
 include(CheckCXXSourceCompiles)
 
 check_cxx_source_compiles(
@@ -789,18 +781,7 @@ Cflags: -I\${includedir}${PC_CFLAGS}\n")
     # Abseil libraries require C++14 as the current minimum standard. When
     # compiled with C++17 (either because it is the compiler's default or
     # explicitly requested), then Abseil requires C++17.
-    _absl_target_compile_features_if_available(${_dll} PUBLIC ${ABSL_INTERNAL_CXX_STD_FEATURE})
-  else()
-    # Note: This is legacy (before CMake 3.8) behavior. Setting the
-    # target-level CXX_STANDARD property to ABSL_CXX_STANDARD (which is
-    # initialized by CMAKE_CXX_STANDARD) should have no real effect, since
-    # that is the default value anyway.
-    #
-    # CXX_STANDARD_REQUIRED does guard against the top-level CMake project
-    # not having enabled CMAKE_CXX_STANDARD_REQUIRED (which prevents
-    # "decaying" to an older standard if the requested one isn't available).
-    set_property(TARGET ${_dll} PROPERTY CXX_STANDARD ${ABSL_CXX_STANDARD})
-    set_property(TARGET ${_dll} PROPERTY CXX_STANDARD_REQUIRED ON)
+    target_compile_features(${_dll} PUBLIC ${ABSL_INTERNAL_CXX_STD_FEATURE})
   endif()
 
   install(TARGETS ${_dll} EXPORT ${PROJECT_NAME}Targets

CMake/AbseilHelpers.cmake

@@ -291,18 +291,7 @@ Cflags: -I\${includedir}${PC_CFLAGS}\n")
       # Abseil libraries require C++14 as the current minimum standard. When
       # compiled with C++17 (either because it is the compiler's default or
       # explicitly requested), then Abseil requires C++17.
-      _absl_target_compile_features_if_available(${_NAME} PUBLIC ${ABSL_INTERNAL_CXX_STD_FEATURE})
-    else()
-      # Note: This is legacy (before CMake 3.8) behavior. Setting the
-      # target-level CXX_STANDARD property to ABSL_CXX_STANDARD (which is
-      # initialized by CMAKE_CXX_STANDARD) should have no real effect, since
-      # that is the default value anyway.
-      #
-      # CXX_STANDARD_REQUIRED does guard against the top-level CMake project
-      # not having enabled CMAKE_CXX_STANDARD_REQUIRED (which prevents
-      # "decaying" to an older standard if the requested one isn't available).
-      set_property(TARGET ${_NAME} PROPERTY CXX_STANDARD ${ABSL_CXX_STANDARD})
-      set_property(TARGET ${_NAME} PROPERTY CXX_STANDARD_REQUIRED ON)
+      target_compile_features(${_NAME} PUBLIC ${ABSL_INTERNAL_CXX_STD_FEATURE})
     endif()
 
     # When being installed, we lose the absl_ prefix.  We want to put it back
@@ -339,10 +328,7 @@ Cflags: -I\${includedir}${PC_CFLAGS}\n")
       # Abseil libraries require C++14 as the current minimum standard.
       # Top-level application CMake projects should ensure a consistent C++
       # standard for all compiled sources by setting CMAKE_CXX_STANDARD.
-      _absl_target_compile_features_if_available(${_NAME} INTERFACE ${ABSL_INTERNAL_CXX_STD_FEATURE})
-
-      # (INTERFACE libraries can't have the CXX_STANDARD property set, so there
-      # is no legacy behavior else case).
+      target_compile_features(${_NAME} INTERFACE ${ABSL_INTERNAL_CXX_STD_FEATURE})
     endif()
   endif()
 
@@ -452,18 +438,7 @@ function(absl_cc_test)
     # Abseil libraries require C++14 as the current minimum standard.
     # Top-level application CMake projects should ensure a consistent C++
     # standard for all compiled sources by setting CMAKE_CXX_STANDARD.
-    _absl_target_compile_features_if_available(${_NAME} PUBLIC ${ABSL_INTERNAL_CXX_STD_FEATURE})
-  else()
-    # Note: This is legacy (before CMake 3.8) behavior. Setting the
-    # target-level CXX_STANDARD property to ABSL_CXX_STANDARD (which is
-    # initialized by CMAKE_CXX_STANDARD) should have no real effect, since
-    # that is the default value anyway.
-    #
-    # CXX_STANDARD_REQUIRED does guard against the top-level CMake project
-    # not having enabled CMAKE_CXX_STANDARD_REQUIRED (which prevents
-    # "decaying" to an older standard if the requested one isn't available).
-    set_property(TARGET ${_NAME} PROPERTY CXX_STANDARD ${ABSL_CXX_STANDARD})
-    set_property(TARGET ${_NAME} PROPERTY CXX_STANDARD_REQUIRED ON)
+    target_compile_features(${_NAME} PUBLIC ${ABSL_INTERNAL_CXX_STD_FEATURE})
   endif()
 
   add_test(NAME ${_NAME} COMMAND ${_NAME})

CMakeLists.txt

@@ -68,7 +68,7 @@ endif()
 option(ABSL_PROPAGATE_CXX_STD
   "Use CMake C++ standard meta features (e.g. cxx_std_14) that propagate to targets that link to Abseil"
   OFF)  # TODO: Default to ON for CMake 3.8 and greater.
-if((${CMAKE_VERSION} VERSION_GREATER_EQUAL 3.8) AND (NOT ABSL_PROPAGATE_CXX_STD))
+if(NOT ABSL_PROPAGATE_CXX_STD)
   message(WARNING "A future Abseil release will default ABSL_PROPAGATE_CXX_STD to ON for CMake 3.8 and up. We recommend enabling this option to ensure your project still builds correctly.")
 endif()