macos: support Apple Universal 2 builds (#1086)
fixes #970
diff --git a/absl/copts/AbseilConfigureCopts.cmake b/absl/copts/AbseilConfigureCopts.cmake
index 942ce90..15d6c89 100644
--- a/absl/copts/AbseilConfigureCopts.cmake
+++ b/absl/copts/AbseilConfigureCopts.cmake
@@ -12,7 +12,49 @@
set(ABSL_BUILD_DLL FALSE)
endif()
-if(CMAKE_SYSTEM_PROCESSOR MATCHES "x86_64|amd64|AMD64")
+if(APPLE AND CMAKE_CXX_COMPILER_ID MATCHES [[Clang]])
+ # Some CMake targets (not known at the moment of processing) could be set to
+ # compile for multiple architectures as specified by the OSX_ARCHITECTURES
+ # property, which is target-specific. We should neither inspect nor rely on
+ # any CMake property or variable to detect an architecture, in particular:
+ #
+ # - CMAKE_OSX_ARCHITECTURES
+ # is just an initial value for OSX_ARCHITECTURES; set too early.
+ #
+ # - OSX_ARCHITECTURES
+ # is a per-target property; targets could be defined later, and their
+ # properties could be modified any time later.
+ #
+ # - CMAKE_SYSTEM_PROCESSOR
+ # does not reflect multiple architectures at all.
+ #
+ # When compiling for multiple architectures, a build system can invoke a
+ # compiler either
+ #
+ # - once: a single command line for multiple architectures (Ninja build)
+ # - twice: two command lines per each architecture (Xcode build system)
+ #
+ # If case of Xcode, it would be possible to set an Xcode-specific attributes
+ # like XCODE_ATTRIBUTE_OTHER_CPLUSPLUSFLAGS[arch=arm64] or similar.
+ #
+ # In both cases, the viable strategy is to pass all arguments at once, allowing
+ # the compiler to dispatch arch-specific arguments to a designated backend.
+ set(ABSL_RANDOM_RANDEN_COPTS "")
+ foreach(_arch IN ITEMS "x86_64" "arm64")
+ string(TOUPPER "${_arch}" _arch_uppercase)
+ string(REPLACE "X86_64" "X64" _arch_uppercase ${_arch_uppercase})
+ foreach(_flag IN LISTS ABSL_RANDOM_HWAES_${_arch_uppercase}_FLAGS)
+ list(APPEND ABSL_RANDOM_RANDEN_COPTS "-Xarch_${_arch}" "${_flag}")
+ endforeach()
+ endforeach()
+ # If a compiler happens to deal with an argument for a currently unused
+ # architecture, it will warn about an unused command line argument.
+ option(ABSL_RANDOM_RANDEN_COPTS_WARNING OFF
+ "Warn if one of ABSL_RANDOM_RANDEN_COPTS is unused")
+ if(ABSL_RANDOM_RANDEN_COPTS AND NOT ABSL_RANDOM_RANDEN_COPTS_WARNING)
+ list(APPEND ABSL_RANDOM_RANDEN_COPTS "-Wno-unused-command-line-argument")
+ endif()
+elseif(CMAKE_SYSTEM_PROCESSOR MATCHES "x86_64|amd64|AMD64")
if (MSVC)
set(ABSL_RANDOM_RANDEN_COPTS "${ABSL_RANDOM_HWAES_MSVC_X64_FLAGS}")
else()
