Interesting. However, I wonder if this truncation is valid. Looking at ISO-10206, it states in section <6.4.6 Assignment-compatibility> : "At any place where the rule of assignment-compatibility is used ... c) it shall be an error if T1 and T2 are compatible, T1 is a string-type or the char-type, and the length of the value of T2 is greater than the capacity of T1;" My interpretation of this, is that in this situation, the statement <AString:=AString+'ML'> should have resulted in an error, since the compiler only allocated a capacity of 1 to AString, yet such a concatenation can never fit within this capacity. Joe.

-----Original Message----- From: Frank Heckenbach [SMTP:frank@g-n-u.de] Sent: Monday, March 18, 2002 8:42 AM To: gpc@gnu.de Subject: Re: Problem with gpc 2.1 RC 3

Prof Abimbola Olowofoyeku wrote:

...

On 17 Mar 2002 at 13:16, Martin Liddle wrote:

...

I have just moved to RC 3. Looking at the list of fixed bugs it is obvious that a lot of work has been done in the last few months; thanks to all concerned. The stricter type checking required a lot of effort to get our code to compile but in fairness did highlight a number of problems in our code; so I think it was time well spent. However I am now stuck because of the following problem:

Program WriteTest;

Procedure ZWriteln(AString:String); Begin AString:=AString+'ML'; Writeln('String [',AString,'] Length is ',Length(AString)); End;

Begin ZWriteln(' '); End.

What I see is that length is reported as 1 i.e. the string concatenation is failing. Is this expected behaviour or a bug?

It is a bug alright. If you pass a string variable rather than a literal to 'ZWriteln', the concatentation is successful. So, something seems to have gone awry somewhere.

No, it's not a bug. `AString' is a formal parameter of undiscriminated schema type. This means it assumes the discriminants (in case of String: Capacity) of the actual parameter. In the example, the actual parameter is a string constant of length 1. It also has capacity 1, since constants can't change, anyway.

So also the parameter has capacity 1 during the execution of `ZWriteln'. Assigning ` ML' (the result of concatenation) to a capacity 1 string results in truncation to ` '. This behaviour is not new, BTW.

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