FreeBSD + Strings --> crash - Gpc

2 Nov 1996


      Hello folks,
perhaps somebody can help me with a strange error which occurs
when using Strings under FreeBSD.  (It does not occur on DJGPP,
EMX, or Linux.)
The error is triggered by the program
Program Crash;
Type
      WrkString = String ( 80 );
Var
      S: WrkString;
begin
      S:= 'A';
      if S = 'A' then
        writeln ( 'Hurra!' );
    end.
It compiles fine, the assembly code looks nice, but it gets a signal
"iot" (whatever that means) when running.  The error happens in the
RTS function _p_string() (see rts/rts-string.c):
/* First arg is always a string or char */
    if (argument_mask & P_STR_FIRST_IS_CHAR)
      {
        c1   = va_arg (p, char);
        s1   = &c1;
        len1 = 1;
      }
    else
      {
        /* It's a string */
        s1   = va_arg (p, char *);
        len1 = va_arg (p, int);             /* <------ SIGIOT */
      }
When examining the variables with gdb, everything looks nice, too.
*p == 'A', etc.
A similar error happens when running the following variant:
Program Crash;
uses
      CPtr;
Var
      C: Char value 'A';
      P: CharPtr;
begin
      P:= @C;
      if P^ = 'A' then
        writeln ( 'Hurra!' );
    end.
It is essential that the type "CharPtr = ^Char" is exported by a
Unit, not declared in the program.
First, we get a warning about assignment of incompatible pointers for
"P:= @C" which is, of course, nonsense, but I can explain it with the
mechanism of forward references in pointer declarations.
Again, the assembler code looks fine, but when running the program,
I get a signal. :(
And again, the error does not occur with DJGPP, EMX, or Linux - only
with FreeBSD.
DOES ANYBODY HAVE AN IDEA?
Yours,
Peter
e-mail:  peter.gerwinski@uni-essen.de
home address:  D"usseldorfer Str. 35, 45145 Essen, Germany
         WWW:  http://agnes.dida.physik.uni-essen.de/~peter/