Clarify prevector::erase and avoid swap-to-clear

sipa · sipa · commit e241a63c2323 · 2017-06-09T13:23:20.000-07:00
diff --git a/src/prevector.h b/src/prevector.h
@@ -387,6 +387,12 @@ class prevector {
     }
 
     iterator erase(iterator first, iterator last) {
+        // Erase is not allowed to the change the object's capacity. That means
+        // that when starting with an indirectly allocated prevector with
+        // size and capacity > N, the result may be a still indirectly allocated
+        // prevector with size <= N and capacity > N. A shrink_to_fit() call is
+        // necessary to switch to the (more efficient) directly allocated
+        // representation (with capacity N and size <= N).
         iterator p = first;
         char* endp = (char*)&(*end());
         if (!std::is_trivially_destructible<T>::value) {
diff --git a/src/script/script.h b/src/script/script.h
@@ -642,8 +642,9 @@ class CScript : public CScriptBase
 
     void clear()
     {
-        // The default std::vector::clear() does not release memory.
-        CScriptBase().swap(*this);
+        // The default prevector::clear() does not release memory
+        CScriptBase::clear();
+        shrink_to_fit();
     }
 };
 

Original file line number	Diff line number	Diff line change
`@@ -642,8 +642,9 @@ class CScript : public CScriptBase`
`642`	`642`
`643`	`643`	`void clear()`
`644`	`644`	`{`
`645`		`- // The default std::vector::clear() does not release memory.`
`646`		`- CScriptBase().swap(*this);`
	`645`	`+ // The default prevector::clear() does not release memory`
	`646`	`+ CScriptBase::clear();`
	`647`	`+ shrink_to_fit();`
`647`	`648`	`}`
`648`	`649`	`};`
`649`	`650`