Comment why we avoid calling free with null

[software/dgc/cdgc.git] / rt / gc / cdgc / bits.d

diff --git a/rt/gc/cdgc/bits.d b/rt/gc/cdgc/bits.d
index 02300ce9b18effe48dbe33c37944bdd2a23a8626..4d2536275f2bd133217d5a639ca6ced3b1ba7971 100644 (file)
--- a/rt/gc/cdgc/bits.d
+++ b/rt/gc/cdgc/bits.d
@@ -62,6 +62,10 @@ struct GCBits
 
     void Dtor()
     {
+        // Even when free() can be called with a null pointer, the extra call
+        // might be significant. On hard GC benchmarks making the test for null
+        // here (i.e. not making the call) can reduce the GC time by almost
+        // ~5%.
         if (data)
         {
             cstdlib.free(data);