[libcxx-commits] [PATCH] D153413: [libc++] Refactor the selection of string's ABI in __config

[Louis Dionne via Phabricator via libcxx-commits]

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This doesn't change the selection, but it expands the conditions to
add comments and make it clearer what's happening. It also removes a
-Wundef instance when we checked __ARM_ARCH_7K__ >= 2 without checking
that it is defined in the first place.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D153413

Files:
  libcxx/include/__config


Index: libcxx/include/__config
===================================================================
--- libcxx/include/__config
+++ libcxx/include/__config
@@ -460,8 +460,17 @@
 
 #  if defined(_LIBCPP_COMPILER_CLANG_BASED)
 
-#    if defined(__APPLE__) && !defined(__i386__) && !defined(__x86_64__) && (!defined(__arm__) || __ARM_ARCH_7K__ >= 2)
-#      define _LIBCPP_ABI_ALTERNATE_STRING_LAYOUT
+#    if defined(__APPLE__)
+#      if defined(__i386__) || defined(__x86_64__)
+// use old string layout on x86_64 and i386
+#      elif defined(__arm__)
+// use old string layout on arm (which does not include aarch64/arm64), except on watch ABIs
+#        if defined(__ARM_ARCH_7K__) && __ARM_ARCH_7K__ >= 2
+#          define _LIBCPP_ABI_ALTERNATE_STRING_LAYOUT
+#        endif
+#      else
+#        define _LIBCPP_ABI_ALTERNATE_STRING_LAYOUT
+#      endif
 #    endif
 
 // Objective-C++ features (opt-in)


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