[PATCH] D70122: [cmake] Disable GCC 9's -Winit-list-lifetime warning

[Pavel Labath via Phabricator via llvm-commits]

labath created this revision.
labath added reviewers: rnk, aaron.ballman.
Herald added a subscriber: mgorny.
Herald added a project: LLVM.

This is a new warning which fires when one stores a reference to the
initializer_list contents in a way which may outlive the
initializer_list which it came from. In llvm this warning is triggered
whenever someone uses the initializer_list ArrayRef constructor.

This is indeed a dangerous thing to do (I myself was bitten by that at
least once), but it is not more dangerous than calling other ArrayRef
constructors with temporary objects -- something which we are used to
and have accepted as a tradeoff for ArrayRef's efficiency.

Currently, this warnings generates so much output that it completely
obscures any actionable warnings, so this patch disables it.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D70122

Files:
  llvm/cmake/modules/HandleLLVMOptions.cmake


Index: llvm/cmake/modules/HandleLLVMOptions.cmake
===================================================================
--- llvm/cmake/modules/HandleLLVMOptions.cmake
+++ llvm/cmake/modules/HandleLLVMOptions.cmake
@@ -588,6 +588,12 @@
   check_cxx_compiler_flag("-Wclass-memaccess" CXX_SUPPORTS_CLASS_MEMACCESS_FLAG)
   append_if(CXX_SUPPORTS_CLASS_MEMACCESS_FLAG "-Wno-class-memaccess" CMAKE_CXX_FLAGS)
 
+  # A GCC 9 warning triggered by ArrayRef.
+  check_cxx_compiler_flag("-Winit-list-lifetime"
+    CXX_SUPPORTS_INIT_LIST_LIFETIME_FLAG)
+  append_if(CXX_SUPPORTS_INIT_LIST_LIFETIME_FLAG "-Wno-init-list-lifetime"
+    CMAKE_CXX_FLAGS)
+
   # The LLVM libraries have no stable C++ API, so -Wnoexcept-type is not useful.
   check_cxx_compiler_flag("-Wnoexcept-type" CXX_SUPPORTS_NOEXCEPT_TYPE_FLAG)
   append_if(CXX_SUPPORTS_NOEXCEPT_TYPE_FLAG "-Wno-noexcept-type" CMAKE_CXX_FLAGS)


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