Use portable posix sigsetjmp to avoid saving signals on linux, in addition to apple platforms.

PiperOrigin-RevId: 693881256

csharp/src/Google.Protobuf/Reflection/FeatureSetDescriptor.g.cs

@@ -1,17 +0,0 @@
-#region Copyright notice and license
-// Protocol Buffers - Google's data interchange format
-// Copyright 2008 Google Inc.  All rights reserved.
-//
-// Use of this source code is governed by a BSD-style
-// license that can be found in the LICENSE file or at
-// https://developers.google.com/open-source/licenses/bsd
-#endregion
-
-namespace Google.Protobuf.Reflection;
-
-internal sealed partial class FeatureSetDescriptor
-{
-    // Canonical serialized form of the edition defaults, generated by embed_edition_defaults.
-    private const string DefaultsBase64 =
-        "ChMYhAciACoMCAEQAhgCIAMoATACChMY5wciACoMCAIQARgBIAIoATABChMY6AciDAgBEAEYASACKAEwASoAIOYHKOgH";
-}

upb/port/def.inc

@@ -178,10 +178,14 @@ Error, UINTPTR_MAX is undefined
 #define UPB_UNREACHABLE() do { assert(0); } while(0)
 #endif
 
-/* UPB_SETJMP() / UPB_LONGJMP(): avoid setting/restoring signal mask. */
-#ifdef __APPLE__
-#define UPB_SETJMP(buf) _setjmp(buf)
-#define UPB_LONGJMP(buf, val) _longjmp(buf, val)
+/* UPB_SETJMP() / UPB_LONGJMP() */
+// Android uses a custom libc that does not implement all of posix, but it has
+// had sigsetjmp/siglongjmp forever on arm and since API 12 on x86. Apple has
+// sigsetjmp, but does not define the posix feature test macro.
+#if defined(__APPLE__) || defined(_POSIX_C_SOURCE) || defined(__ANDROID__)
+// avoid setting/restoring signal mask, which involves costly syscalls
+#define UPB_SETJMP(buf) sigsetjmp(buf, 0)
+#define UPB_LONGJMP(buf, val) siglongjmp(buf, val)
 #elif defined(WASM_WAMR)
 #define UPB_SETJMP(buf) 0
 #define UPB_LONGJMP(buf, val) abort()