address clanker review comments

Author: scottgerring

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

@@ -31,16 +31,15 @@
  */
 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.
+ * The symbol always exists, but the USDT is only emitted 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

@@ -12,7 +12,8 @@
  * dd_sample_flag_check confirmed that ptr carries the sample flag,
  * meaning this allocation was previously sampled.
  *
- * Fires the ddheap:free USDT with the user-visible pointer, then returns
+ * Fires the ddheap:free USDT (when live-heap tracking is enabled) with the
+ * user-visible pointer, then returns
  * the raw pointer and adjusted size that the caller must forward to the
  * real deallocator. On x86-64 the size grows by DD_HEADER_BYTES to cover
  * the header that was reserved at allocation time; on arm64 the size is
@@ -21,10 +22,10 @@
 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
+     * time, so the profiler can correlate the two events by address. Safe to
+     * call unconditionally: dd_probe_free is a no-op USDT-wise when live-heap
+     * tracking is off. */
     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

@@ -18,13 +18,16 @@
  */
 
 #include <datadog/heap/probes.h>
+#include <datadog/heap/sample_flag.h>
 
 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) {
+#if DD_HEAP_LIVE_TRACKING
     USDT(ddheap, free, ptr);
-}
-#endif
+#else
+    (void)ptr;
+#endif
+}