[fpc-devel] StrPos giving a access violation

Jonas Maebe jonas.maebe at elis.ugent.be
Mon Dec 12 13:45:36 CET 2005

On 12 dec 2005, at 13:30, Micha Nelissen wrote:

>> Taken from Delphi 7 help:
>> Mixing Delphi strings and null-terminated strings
>> * You can also use Pointer(S) to cast a long string to an untyped  
>> pointer. But if S is empty, the typecast returns nil.
>> * PChar(S) always returns a pointer to a memory block; if S is  
>> empty, a pointer to #0 is returned.
> Thanks, that is very ugly. That means that PChar(Pointer(MyStr)) is  
> not the same as PChar(MyStr) which is not very pascalish IMHO, but ok.

It happens in more in Pascal. For example, single(longint_var) is  
also not the same as single(pointer(longint_var)) (let's assume a  
32bit system). In the former case, the longint is convert to a  
floating point number with the same value. In the latter case, you  
get a floating point number with the same bit pattern as that  
original longint (which may be a valid or invalid floating point  
number, and whose value is almost certainly different from the  
longint's value, except in case of 0).


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