fix(profiling): crash in ddtrace_get_profiling_context

morrisonlevi · morrisonlevi · commit 1f37473291de · 2026-01-11T11:24:38.000-07:00
diff --git a/ext/profiling.c b/ext/profiling.c
@@ -8,7 +8,11 @@ ZEND_EXTERN_MODULE_GLOBALS(ddtrace);
 
 DDTRACE_PUBLIC struct ddtrace_profiling_context ddtrace_get_profiling_context(void) {
     struct ddtrace_profiling_context context = {0, 0};
-    if (DDTRACE_G(active_stack) && DDTRACE_G(active_stack)->root_span && get_DD_TRACE_ENABLED()) {
+    // NOTE: `active_stack->active` may legitimately be NULL during span close (e.g. when closing the last span on a
+    // stack, `ddtrace_close_top_span_without_stack_swap()` updates it before running additional logic that may still
+    // allocate, such as JSON encoding during sampling decisions). Allocation profiling can call into this function
+    // from within those allocations, so treat "no active span" as "no profiling context" instead of dereferencing.
+    if (DDTRACE_G(active_stack) && DDTRACE_G(active_stack)->root_span && DDTRACE_G(active_stack)->active && get_DD_TRACE_ENABLED()) {
         context.local_root_span_id = DDTRACE_G(active_stack)->root_span->span_id;
         context.span_id = SPANDATA(DDTRACE_G(active_stack)->active)->span_id;
     }
