Break on nullptr return address in UnwindImpl on RISC-V

PiperOrigin-RevId: 914222352
Change-Id: Iff9028a38e878465961f71e90484c2a62ed89132

absl/debugging/internal/stacktrace_emscripten-inl.inc

@@ -74,10 +74,19 @@ static int UnwindImpl(void **result, uintptr_t *frames, int *sizes,
   size =
       static_cast<int>(emscripten_stack_unwind_buffer(pc, stack, kStackLength));
 
-  int result_count = size - skip_count;
+  int num_frames = size - skip_count;
-  if (result_count < 0) result_count = 0;
+  if (num_frames < 0) num_frames = 0;
-  if (result_count > max_depth) result_count = max_depth;
+  if (num_frames > max_depth) num_frames = max_depth;
-  for (int i = 0; i < result_count; i++) result[i] = stack[i + skip_count];
+
+  int result_count = 0;
+  for (int i = 0; i < num_frames; i++) {
+    int stack_index = i + skip_count;
+    // Follow x86 and stop if the return address is null (end of stack).
+    if (stack[stack_index] == nullptr) {
+      break;
+    }
+    result[result_count++] = stack[stack_index];
+  }
 
   if (IS_STACK_FRAMES) {
     // No implementation for finding out the stack frames yet.

absl/debugging/internal/stacktrace_riscv-inl.inc

@@ -142,6 +142,10 @@ static int UnwindImpl(void **result, uintptr_t *frames, int *sizes,
   void *return_address = nullptr;
   while (frame_pointer && n < max_depth) {
     return_address = frame_pointer[-1];
+    // Follow x86 and stop if the return address is null (end of stack).
+    if (return_address == nullptr) {
+      break;
+    }
 
     // The absl::GetStackFrames routine is called when we are in some
     // informational context (the failure signal handler for example).  Use the

absl/debugging/stacktrace_test.cc

@@ -378,4 +378,14 @@ TEST(StackTrace, NestedSignal) {
 }
 #endif
 
+TEST(StackTrace, NoNullptrInPopulatedRange) {
+  constexpr int kMaxDepth = 1024;
+  void* results[kMaxDepth];
+  int depth = absl::GetStackTrace(results, kMaxDepth, 0);
+  for (int i = 0; i < depth; ++i) {
+    EXPECT_NE(results[i], nullptr) << "Unexpected nullptr found at index " << i;
+  }
+}
+
+
 }  // namespace