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base/allocator.h: clarify use of delete operator

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Issue #1571
This commit is contained in:
Norman Feske 2015-06-10 11:34:53 +02:00 committed by Christian Helmuth
parent b64f23d4c3
commit 5317cca031
1 changed files with 17 additions and 1 deletions
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18
repos/base/include/base/allocator.h
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@ -269,7 +269,23 @@ void Genode::destroy(DEALLOC && dealloc, T *obj)
/* call destructors */ /* call destructors */
obj->~T(); obj->~T();
/* free memory at the allocator */ /*
* Free memory at the allocator
*
* We have to use the delete operator instead of just calling
* 'dealloc.free' because the 'obj' pointer might not always point to the
* begin of the allocated block:
*
* If 'T' is the base class of another class 'A', 'obj' may refer
* to an instance of 'A'. In particular when 'A' used multiple inheritance
* with 'T' not being the first inhertited class, the pointer to the actual
* object differs from 'obj'.
*
* Given the pointer to the base class 'T', however, the delete operator is
* magically (by the means of the information found in the vtable of 'T')
* able to determine the actual pointer to the instance of 'A' and passes
* this pointer to 'free'.
*/
operator delete (obj, dealloc); operator delete (obj, dealloc);
} }