Why does Str() give "W1057 Implicit string cast from 'ShortString' to 'string'"?

Question

Consider:

function x_StrZero(N: Double; W: Integer; D: Integer = 0): String;
var S : String;
begin
  Str(N:W:D,S);   
  S := Trim(S);

This gives W1057 Implicit string cast from 'ShortString' to 'string'

The online doc says:

procedure Str(const X [: Width [:Decimals]]; var S: String);

but also

Notes: However, on using this procedure, the compiler may issue a warning: W1057 Implicit string cast from '%s' to '%s' (Delphi).

Why would this be?

I would like to prevent this ugly workaround:

function x_StrZero(N: Double; W: Integer; D: Integer = 0): String;
var
  S : String;
  SS : ShortString;
begin
  Str(N:W:D,SS);
  S := Trim(String(SS));

I have read Why does Delphi warn when assigning ShortString to string? but that does not answer this.

just a wild guess, did you tried S:Ansistring and {$O-} ? Str is ancient function from TurboPascal, probably asm implementation over TP strings. While IntToStr lacks that functionality, i'd anyway avoid those ancient procedures. — Arioch 'The, Sep 19 '12 at 10:47
TJclNumericFormat and function IntToStrZeroPad(Value, Count: Integer): string; may be feasible replacements too — Arioch 'The, Sep 19 '12 at 10:49
DOS-era Turbo-pascal compatibility syntax. You can't add your own functions with func(a:b:c,d) syntax. :-) — Warren P, Sep 20 '12 at 00:36

score 9 · Accepted Answer · answered Sep 19 '12 at 11:02

Str(N:W:D,S);

gets compiled as

S := System._Str2Ext(N, W, D);

where System._Str2Ext is a function with a return type of ShortString. It gets converted to string in the assignment to S. The warning, while not easily readable, is correct, there is an implicit conversion at that point. So either rework the code to not have an implicit conversion there by avoiding Str, or turn off the warning, or ignore the warning.

Thanks, I did not find that in System – Jan Doggen Sep 19 '12 at 14:51 — Jan Doggen, Sep 19 '12 at 14:51

iMan Biglari · Answer 2 · 2012-09-19T11:12:07.787

0

You can turn that specific warning off. It's just a reminder, and most of the time your program works fine. I guess the compiler still sees String as ShortString in the functions which are built into it like Str() and Writeln().

edited Sep 19 '12 at 11:12

answered Sep 19 '12 at 10:46

iMan Biglari

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You meant Shortstring rather than AnsiStirng probably ? And WriteLn finely works with string==UnicodeString – Arioch 'The Sep 19 '12 at 11:11
Yes my mistake. I meant routines which are replaced by the compiler directly – iMan Biglari Sep 19 '12 at 11:11

Why does Str() give "W1057 Implicit string cast from 'ShortString' to 'string'"?

2 Answers2