chore(heap-profiling): if a user doesnt opt into live heap, ensure the USDT does not land in the process

Author: scottgerring

libdd-profiling-heap-sampler/include/datadog/heap/probes.h

@@ -31,10 +31,16 @@
  */
 void dd_probe_alloc(void *user, uint64_t size, uint64_t weight);
 
+#if DD_HEAP_LIVE_TRACKING
 /*
  * Emits the `ddheap:free` USDT.
  *   ptr - user-visible pointer being freed
+ *
+ * Only available when compiled with live-heap tracking. The absence of
+ * the `ddheap:free` note in .note.stapsdt signals to external profilers
+ * that this binary does not support live-heap correlation.
  */
 void dd_probe_free(void *ptr);
+#endif
 
 #endif

libdd-profiling-heap-sampler/src/allocation_freed.c

@@ -22,7 +22,9 @@ dd_alloc_freed_t dd_allocation_freed_slow(void *ptr, void *raw, size_t size,
                                           size_t alignment) {
     /* Fire with the user-visible pointer, matching what was reported at alloc
      * time, so the profiler can correlate the two events by address. */
+#if DD_HEAP_LIVE_TRACKING
     dd_probe_free(ptr);
+#endif
 
     dd_alloc_freed_t out = {
         /* Return the raw pointer so the caller passes the real allocation base

libdd-profiling-heap-sampler/src/probes.c

@@ -23,6 +23,8 @@ void dd_probe_alloc(void *user, uint64_t size, uint64_t weight) {
     USDT(ddheap, alloc, user, size, weight);
 }
 
+#if DD_HEAP_LIVE_TRACKING
 void dd_probe_free(void *ptr) {
     USDT(ddheap, free, ptr);
-}
+}
+#endif