I have encountered a couple problems with strings in the most recent GPC beta version. Most of the problems are due to missing range checks, e.g. when assigning a string to a shorter string, or passing a string to a procedure with a shorter string as formal parameter.

1) The program below illustrates some of these problems:

program Test5;

var s1 : string [500]; s2 : string [10];

type str5 = string [5];

procedure p1 (s : str5); begin Writeln (s.capacity, ' ', Length (s)); end;

begin s1 := 'This is a relatively long string';

s2 := s1; { Copies all of s1 to s2; not just the first 10 characters }

p1 (s1); { Passes all of s1 to procedure p1 } p1 (s2); end.

Before exiting with a SIGSEGV exception (under DJGPP), the program prints

5 32 5 32

2) Another facet of the problem occurs when reading strings from a text file with Read[ln] (F, stringVar).

If you call Readln, the program will read from the file until the next CR/LF, no matter the size (length) of stringVar, and try to copy the entire line to the variables stringVar (which will almost surely crash the program somehow; but not necessarily in the call to Readln. The SIGSEGV exception could come later, and with a stack trace which makes no sense).

On the other hand, Read (F, stringVar) only reads a maximum of Length(stringVar) characters [as it should].

Jesper Lund