[PATCH] D133771: Add a "Potentially Breaking Changes" section to the Clang release notes

[Aaron Ballman via Phabricator via cfe-commits]

aaron.ballman created this revision.
aaron.ballman added reviewers: tstellar, mgorny, jyknight.
Herald added a project: All.
aaron.ballman requested review of this revision.
Herald added a project: clang.

Sometimes we make changes to the compiler that we expect may cause disruption for users. For example, we may strengthen a warning to default to be an error, or fix an accepts-invalid bug that's been around for a long time, etc which may cause previously accepted code to now be rejected. Rather than hope users discover that information by reading all of the release notes, it's better that we call these out in one location at the top of the release notes.

Based on feedback collected in the discussion at:
https://discourse.llvm.org/t/configure-script-breakage-with-the-new-werror-implicit-function-declaration/65213/


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D133771

Files:
  clang/docs/ReleaseNotes.rst


Index: clang/docs/ReleaseNotes.rst
===================================================================
--- clang/docs/ReleaseNotes.rst
+++ clang/docs/ReleaseNotes.rst
@@ -36,6 +36,26 @@
 the current one. To see the release notes for a specific release, please
 see the `releases page <https://llvm.org/releases/>`_.
 
+Potentially Breaking Changes
+============================
+These changes are ones which we think may surprise users when upgrading to
+Clang |release| because of the opportunity they pose for disruption to existing
+code bases.
+
+- Clang will now correctly diagnose as ill-formed a constant expression where an
+  enum without a fixed underlying type is set to a value outside the range of
+  the enumeration's values. Due to the extended period of time this bug was
+  present in major C++ implementations (including Clang), this error has the
+  ability to be downgraded into a warning (via: -Wno-error=enum-constexpr-conversion)
+  to provide a transition period for users. This diagnostic is expected to turn
+  into an error-only diagnostic in the next Clang release. Fixes
+  `Issue 50055: <https://github.com/llvm/llvm-project/issues/50055>`_.
+- ``-Wincompatible-function-pointer-types`` now defaults to an error in all C
+  language modes. It may be downgraded to a warning with
+  ``-Wno-error=incompatible-function-pointer-types`` or disabled entirely with
+  ``-Wno-implicit-function-pointer-types``.
+
+
 What's New in Clang |release|?
 ==============================
 
@@ -99,14 +119,6 @@
 
 Improvements to Clang's diagnostics
 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
-- Clang will now correctly diagnose as ill-formed a constant expression where an
-  enum without a fixed underlying type is set to a value outside the range of
-  the enumeration's values. Due to the extended period of time this bug was
-  present in major C++ implementations (including Clang), this error has the
-  ability to be downgraded into a warning (via: -Wno-error=enum-constexpr-conversion)
-  to provide a transition period for users. This diagnostic is expected to turn
-  into an error-only diagnostic in the next Clang release. Fixes
-  `Issue 50055: <https://github.com/llvm/llvm-project/issues/50055>`_.
 - Clang will now check compile-time determinable string literals as format strings.
   Fixes `Issue 55805: <https://github.com/llvm/llvm-project/issues/55805>`_.
 - ``-Wformat`` now recognizes ``%b`` for the ``printf``/``scanf`` family of
@@ -119,10 +131,6 @@
   potential false positives, this diagnostic will not diagnose use of the
   ``true`` macro (from ``<stdbool.h>>`) in C language mode despite the macro
   being defined to expand to ``1``.
-- ``-Wincompatible-function-pointer-types`` now defaults to an error in all C
-  language modes. It may be downgraded to a warning with
-  ``-Wno-error=incompatible-function-pointer-types`` or disabled entirely with
-  ``-Wno-implicit-function-pointer-types``.
 - Clang will now print more information about failed static assertions. In
   particular, simple static assertion expressions are evaluated to their
   compile-time value and printed out if the assertion fails.


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