[PATCH] D75199: Build fix: Turn off _GLIBCXX_DEBUG on gcc 9

[Nicolai Hähnle via Phabricator via llvm-commits]

nhaehnle updated this revision to Diff 247506.
nhaehnle added a comment.

Thank you all for the advice.

Changing the patch to use a compile check and fall back to
_GLIBCXX_ASSERTIONS.


Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D75199/new/

https://reviews.llvm.org/D75199

Files:
  llvm/cmake/modules/HandleLLVMOptions.cmake


Index: llvm/cmake/modules/HandleLLVMOptions.cmake
===================================================================
--- llvm/cmake/modules/HandleLLVMOptions.cmake
+++ llvm/cmake/modules/HandleLLVMOptions.cmake
@@ -77,7 +77,22 @@
 
 if(LLVM_ENABLE_EXPENSIVE_CHECKS)
   add_definitions(-DEXPENSIVE_CHECKS)
-  add_definitions(-D_GLIBCXX_DEBUG)
+
+  # In some libstdc++ versions, std::min_element is not constexpr when
+  # _GLIBCXX_DEBUG is enabled.
+  CHECK_CXX_SOURCE_COMPILES("
+    #define _GLIBCXX_DEBUG
+    #include <algorithm>
+    int main(int argc, char** argv) {
+      static constexpr int data[] = {0, 1};
+      constexpr const int* min_elt = std::min_element(&data[0], &data[2]);
+      return 0;
+    }" CXX_SUPPORTS_GLIBCXX_DEBUG)
+  if(CXX_SUPPORTS_GLIBCXX_DEBUG)
+    add_definitions(-D_GLIBCXX_DEBUG)
+  else()
+    add_definitions(-D_GLIBCXX_ASSERTIONS)
+  endif()
 endif()
 
 string(TOUPPER "${LLVM_ABI_BREAKING_CHECKS}" uppercase_LLVM_ABI_BREAKING_CHECKS)


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