[fpc-devel] mising ansi string ref increase

[Martin]

Ok I reproduced it. (compiled  with -gh -gt -O1 => but I am not sure it 
matters

Question: Is it some wrong doing of me? or shall i report it as bug?

In Foo, "s" is supposed to be a copy of "x" => the string should have a 
ref count of 2, and the modification of x, should make a copy of the 
string.
afaik the output should be "a" => but it is "X"

You can also set x:='' => which will be random in output

program Project1;

{$mode objfpc}{$H+}

var
   x: String;

procedure Foo(const s: String);
begin
   x[1]:='X';  //  x:='';
   writeln(s);
end;

procedure Bar;
begin
   SetLength(x,1);
   x[1]:= 'a';
end;

{$R *.res}

begin
   Bar;
   Foo(x);
   readln;
end.


On 22/07/2010 03:10, Martin wrote:
> I have an odd case (bug ?)
> But I am unable to reproduce on a simple example.
>
> Debugger output, and assembler both suggests it's in the compilation.
> fpc from trunk a few weeks ago. using -OpPENTIUMM   -O1
>
> one procedure is declared as
>     procedure SetFoldState(const AValue: String);
>
> another one calls this as follows
>     if FPendingFoldState <> '' then
>       SetFoldState(FPendingFoldState);
>
> FPendingFoldState is a variable (String) of the object (both methods 
> belong to the same object too)
>
> Now in SetFoldstate is a line:
>   FPendingFoldState:='';
>
> and after this AValue becomes corrupt
>
> The assembler of the calling code (from -al)
> # [6541] if FPendingFoldState <> '' then
>     movl    -4(%ebp),%eax
>     movl    1352(%eax),%eax
>     testl    %eax,%eax
>     je    .Lj12594
> .Ll3371:
> # [6542] SetFoldState(FPendingFoldState);
>     movl    -4(%ebp),%eax
>     movl    1352(%eax),%edx
>     movl    -4(%ebp),%eax
>     call    SYNEDIT_TCUSTOMSYNEDIT_$__SETFOLDSTATE$ANSISTRING
> .Lj12594:
>
> There is no ansistring inc ref (both methods are in the same file, and 
> yes {$H+}
>
> Trying to reproduce in a smaller example did not bring results....
>
> Anyone any idea, if there s any code that could cause such an 
> "optimization" ?
>
> Martin
>
>
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