Dennis <de...@avidsoft.com.hk> schrieb am Fr., 24. Aug. 2018, 13:11: > The run results: > Object call Time Taken Seconds: 2.1899964194744825E-001 > Interface call Time Taken Seconds: 2.7999999001622200E-001 > > so, the time difference is about 27% > > > My question is, where is this extra time spent? > > I am assuming an interface variable has a table with entries storing ( > pointer to the object instance AND an offset of method address in the > Virtual Method Table of that object.) > > Am I correct? >
Using an interface is always calling virtual methods. It's however a table that contains pointers to compiler generated wrappers that adjust the Self Pointer and call the correct method. > What is the memory occupied by the interface variable? > I know the sizeof(i) = 8 (in 64 bit windows), but what is the size of > the instance? > The instance is essentially only the VMT, cause for interfaces implemented by FPC classes the interface variable points to a shifted Self pointer that is "fixed" c the wrappers mentioned above. Regards, Sven
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