From c7c1046d492eb3c956868a66a5a66f814808838b Mon Sep 17 00:00:00 2001
From: Dana Robinson <43805+derobins@users.noreply.github.com>
Date: Wed, 2 Dec 2020 05:32:22 -0800
Subject: Fix autotools clang debug optimization level w/ older clang and Xcode
 versions (#146)

* Fixes clang debug optimization level w/ Autotools

NOTE: This was only released in HDF5 1.10.7, so only the 1.10
      branch needs a note in RELEASE.txt.

* Updates the clang -Og setting with a version check w/ autotools

* Sets -Og when clang >= 4.0 or Xcode >= 9.0
* Older versions get -O1
* Autotools only
---
 config/clang-flags | 14 ++++++++++++--
 1 file changed, 12 insertions(+), 2 deletions(-)

diff --git a/config/clang-flags b/config/clang-flags
index e539a3f..e7b51a3 100644
--- a/config/clang-flags
+++ b/config/clang-flags
@@ -56,7 +56,10 @@ load_clang_arguments()
 #
 if test "X-" = "X-$cc_flags_set"; then
     # clang -v will return version number following "clang" on Linux machines,
-    # but on Macs the version number will follow "Apple LLVM version"
+    # but on Xcode the version number will follow "Apple LLVM version"
+    # Note that the Xcode reported LLVM version doesn't match the canonical
+    # LLVM version, so you'll need to do different version checks for
+    # Xcode.
     cc_version="`$CC $CFLAGS $H5_CFLAGS -v 2>&1 |\
         grep 'clang version' | sed 's/.*clang version \([-a-z0-9\.]*\).*/\1/'`"
     if test -n "$cc_version"; then
@@ -160,9 +163,16 @@ if test "X-clang" = "X-$cc_vendor" -o "X-Apple LLVM" = "X-$cc_vendor"; then
     ################
 
     HIGH_OPT_CFLAGS="-O3"
-    DEBUG_OPT_CFLAGS="-Og"
     NO_OPT_CFLAGS="-O0"
 
+    # -Og is only understood by clang 4+ and Xcode 9+
+    # Otherwise use -O1 (which is what -Og usually equates to)
+    if test "X-clang" = "X-$cc_vendor" -a $cc_vers_major -ge 4 -o "X-Apple LLVM" = "X-$cc_vendor" -a $cc_vers_major -ge 9; then
+        DEBUG_OPT_CFLAGS="-Og"
+    else
+        DEBUG_OPT_CFLAGS="-O1"
+    fi
+
     ############
     # Warnings #
     ############
-- 
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