[fpc-pascal] Weird string behavior

Jonas Maebe jonas.maebe at elis.ugent.be
Mon Jul 25 23:23:23 CEST 2016

On 25/07/16 23:07, Mattias Gaertner wrote:
> DefaultSystemCodePage = 1252
> s3 = "abcdef" cp = 65001

Thanks. So the rule for concatenation appears to be:
* the dynamic code page of the result of a string concatenation is that 
of the left operand (except if it's an empty string, then it's that of 
the right operand)
* the declared code page of the final concatenation result is that of 
the left operand

You then process the assignment as if you are assigning a string with 
the above declared/dynamic code page to whatever you are assigning the 
result of the concatenation to (which means no code page conversion in 
case the declared code pages match, like in the above case).

That's indeed not what FPC does currently. It's mainly complicated by 
the fact that FPC contains optimised helpers to avoid the final 
assignment if possible and directly concatenate into the destination 
when possible (those helpers right now only get passed the declared code 
page of the final destination, and not that of the concatenation, and 
hence virtually always convert the result to the dynamic code page of 
the destination at this time -- there are some exceptions for rawbytestring)


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