diff --git a/.github/workflows/bazel_tests.yml b/.github/workflows/bazel_tests.yml
index 2cf83dfa11..caa5289645 100644
--- a/.github/workflows/bazel_tests.yml
+++ b/.github/workflows/bazel_tests.yml
@@ -75,6 +75,11 @@ jobs:
         run: echo "CC=${{ matrix.CC }}" >> $GITHUB_ENV
       - name: Run tests
         run: cd ${{ github.workspace }} && ${{ matrix.BAZEL }} ${{ matrix.startup-flags }} ${{ matrix.BAZEL_CMD || 'test' }} --test_output=errors ${{ steps.bazel-cache.outputs.cache_args }} ${{ matrix.targets || '...' }} ${{ matrix.flags }}
+      - uses: actions/upload-artifact@v3
+        with:
+          name: logs
+          path: |
+            **/*.log
 
   no-python:
     runs-on: ubuntu-20-large
diff --git a/upb/mem/arena.h b/upb/mem/arena.h
index 4586b077e4..1ae0d37d17 100644
--- a/upb/mem/arena.h
+++ b/upb/mem/arena.h
@@ -76,7 +76,8 @@ UPB_INLINE size_t _upb_ArenaHas(upb_Arena* a) {
 
 UPB_API_INLINE void* upb_Arena_Malloc(upb_Arena* a, size_t size) {
   size = UPB_ALIGN_MALLOC(size);
-  if (UPB_UNLIKELY(_upb_ArenaHas(a) < size)) {
+  size_t span = size + UPB_ASAN_GUARD_SIZE;
+  if (UPB_UNLIKELY(_upb_ArenaHas(a) < span)) {
     return _upb_Arena_SlowMalloc(a, size);
   }
 
@@ -87,18 +88,7 @@ UPB_API_INLINE void* upb_Arena_Malloc(upb_Arena* a, size_t size) {
   UPB_ASSERT(UPB_ALIGN_MALLOC(size) == size);
   UPB_UNPOISON_MEMORY_REGION(ret, size);
 
-  h->ptr += size;
-
-#if UPB_ASAN
-  {
-    size_t guard_size = 32;
-    if (_upb_ArenaHas(a) >= guard_size) {
-      h->ptr += guard_size;
-    } else {
-      h->ptr = h->end;
-    }
-  }
-#endif
+  h->ptr += span;
 
   return ret;
 }
@@ -112,7 +102,8 @@ UPB_API_INLINE void upb_Arena_ShrinkLast(upb_Arena* a, void* ptr,
   _upb_ArenaHead* h = (_upb_ArenaHead*)a;
   oldsize = UPB_ALIGN_MALLOC(oldsize);
   size = UPB_ALIGN_MALLOC(size);
-  UPB_ASSERT((char*)ptr + oldsize == h->ptr);  // Must be the last alloc.
+  // Must be the last alloc.
+  UPB_ASSERT((char*)ptr + oldsize == h->ptr - UPB_ASAN_GUARD_SIZE);
   UPB_ASSERT(size <= oldsize);
   h->ptr = (char*)ptr + size;
 }
diff --git a/upb/port/def.inc b/upb/port/def.inc
index c1cf36f287..e9a4ceeaff 100644
--- a/upb/port/def.inc
+++ b/upb/port/def.inc
@@ -273,8 +273,23 @@
  * expected behavior.
  */
 
-#if defined(__SANITIZE_ADDRESS__)
+/* Due to preprocessor limitations, the conditional logic for setting
+ * UPN_CLANG_ASAN below cannot be consolidated into a portable one-liner.
+ * See https://gcc.gnu.org/onlinedocs/cpp/_005f_005fhas_005fattribute.html.
+ */
+#if defined(__has_feature)
+#if __has_feature(address_sanitizer)
+#define UPB_CLANG_ASAN 1
+#else
+#define UPB_CLANG_ASAN 0
+#endif
+#else
+#define UPB_CLANG_ASAN 0
+#endif
+
+#if defined(__SANITIZE_ADDRESS__) || UPB_CLANG_ASAN
 #define UPB_ASAN 1
+#define UPB_ASAN_GUARD_SIZE 32
 #ifdef __cplusplus
 extern "C" {
 #endif
@@ -289,6 +304,7 @@ void __asan_unpoison_memory_region(void const volatile *addr, size_t size);
   __asan_unpoison_memory_region((addr), (size))
 #else
 #define UPB_ASAN 0
+#define UPB_ASAN_GUARD_SIZE 0
 #define UPB_POISON_MEMORY_REGION(addr, size) \
   ((void)(addr), (void)(size))
 #define UPB_UNPOISON_MEMORY_REGION(addr, size) \
diff --git a/upb/port/undef.inc b/upb/port/undef.inc
index e1752f72f6..2a88977987 100644
--- a/upb/port/undef.inc
+++ b/upb/port/undef.inc
@@ -62,6 +62,8 @@
 #undef UPB_POISON_MEMORY_REGION
 #undef UPB_UNPOISON_MEMORY_REGION
 #undef UPB_ASAN
+#undef UPB_ASAN_GUARD_SIZE
+#undef UPB_CLANG_ASAN
 #undef UPB_TREAT_PROTO2_ENUMS_LIKE_PROTO3
 #undef UPB_DEPRECATED
 #undef UPB_GNUC_MIN
diff --git a/upb/reflection/oneof_def.c b/upb/reflection/oneof_def.c
index e33dba953f..8ac974bab2 100644
--- a/upb/reflection/oneof_def.c
+++ b/upb/reflection/oneof_def.c
@@ -136,7 +136,8 @@ void _upb_OneofDef_Insert(upb_DefBuilder* ctx, upb_OneofDef* o,
   // TODO(salo): More redundant work happening here.
   const bool name_exists = upb_strtable_lookup2(&o->ntof, name, size, NULL);
   if (UPB_UNLIKELY(name_exists)) {
-    _upb_DefBuilder_Errf(ctx, "oneof fields have the same name (%s)", name);
+    _upb_DefBuilder_Errf(ctx, "oneof fields have the same name (%.*s)",
+                         (int)size, name);
   }
 
   const bool ok = upb_inttable_insert(&o->itof, number, v, ctx->arena) &&