Avoid regressions in clang nullability checks

Clang 15 (and still as of 16) lost the ability to understand null checks in
conditionals, which is supposed to suppress these warnings.  For now, work
around some, and suppress others.

The suppression boilerplate here is noisy and ugly, and hopefully temporary.
It should be removed once the issue is fixed in clang.

See https://github.com/llvm/llvm-project/issues/63018

1 files changed, 23 insertions, 0 deletions

diff --git a/src/warnings.h b/src/warnings.h
new file mode 100644
index 00000000..4fdec095
--- /dev/null
+++ b/src/warnings.h
@@ -0,0 +1,23 @@
+// Copyright 2019-2024 David Robillard <d@drobilla.net>
+// SPDX-License-Identifier: ISC
+
+#ifndef SERD_SRC_WARNINGS_H
+#define SERD_SRC_WARNINGS_H
+
+#if defined(__clang__)
+
+/// Clang 15 null checking regressed, so we need to suppress it sometimes
+#  define SERD_DISABLE_NULL_WARNINGS \
+    _Pragma("clang diagnostic push") \
+    _Pragma("clang diagnostic ignored \"-Wnullable-to-nonnull-conversion\"")
+
+#  define SERD_RESTORE_WARNINGS _Pragma("clang diagnostic pop")
+
+#else
+
+#  define SERD_DISABLE_NULL_WARNINGS
+#  define SERD_RESTORE_WARNINGS
+
+#endif
+
+#endif // SERD_SRC_WARNINGS_H