Re[2]: [fpc-devel] Found two Delphi incompatibilities
Op Thu, 31 Aug 2006, schreef Sergei Gorelkin: > What makes a difference is actually TStrings.SetTextStr implementation. > Delphi accesses the argument as null-terminated string, so it works perfectly > well even without conversion. FPC implementation treats argument as > AnsiString, accesses its Length field and eventually segfaults... I think FPC's implementation is correct, because, as I read the documentation, it isn't specified that the string cannot contain #0. So, you need to use the actual length of the string. Daniël___ fpc-devel maillist - fpc-devel@lists.freepascal.org http://lists.freepascal.org/mailman/listinfo/fpc-devel
Re[2]: [fpc-devel] Found two Delphi incompatibilities
On Thu, 31 Aug 2006, Sergei Gorelkin wrote:
Thursday, August 31, 2006, 12:35:33 PM, Michael wrote:
MVC> On Thu, 31 Aug 2006, Sergei Gorelkin wrote:
Hello,
While porting some Delphi code, I found the following two
incomatibility issues. Should I report them as bugs?
Sample 1: It compiles both in Delphi and FPC, but FPC executable fails
at runtime. Delphi inserts temporary string variable and conversion
(array of char -> string), but FPC treats the pointer literally.
MVC> Did you check the '@ returns typed pointer' setting in FPC ?
Oops... That was a false alarm - FPC compiler behaves the same way as
Delphi here. They both generate conversion code in {$T+} and do not
generate it in {$T-}.
So my sample appears to be legal only in {$T+}, which isn't a default.
What makes a difference is actually TStrings.SetTextStr implementation.
Delphi accesses the argument as null-terminated string, so it works perfectly
well even without conversion. FPC implementation treats argument as
AnsiString, accesses its Length field and eventually segfaults...
We should check that.
-
const
TestData: array[0..7] of Char = 'abc'#10'def'#0;
procedure Test1;
var
sl: TStringList;
begin
sl := TStringList.Create;
sl.Text := string(@TestData[0]); // <- fails here
sl.Free;
end;
-
Sample 2: This one compiles with Delphi (again, it inserts necessary
conversion Wide -> Ansi), but does not compile with FPC, neither in
objfpc nor in Delphi mode.
-
function Test2: string;
var
buf: array[0..255] of char;
len: Integer;
begin
{ (skipped) I read USB string descriptor into buf. After that,
buf[0] contains length of descriptor in bytes, buf[1] = 3,
and rest is filled with Unicode chars. Now I want to convert it into
ASCII...
}
len := Integer(buf[0]) shr 1;
SetString(result, PWideChar(@buf[2]), len-1);
end;
MVC> What is the error ?
It is 'Incompatible type for arg no.2: Got "PWideChar", expected
"PChar"'.
Seems like a missing overloaded version of SetString()
Michael.
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Re[2]: [fpc-devel] Found two Delphi incompatibilities
Thursday, August 31, 2006, 12:35:33 PM, Michael wrote:
MVC> On Thu, 31 Aug 2006, Sergei Gorelkin wrote:
>> Hello,
>>
>> While porting some Delphi code, I found the following two
>> incomatibility issues. Should I report them as bugs?
>>
>> Sample 1: It compiles both in Delphi and FPC, but FPC executable fails
>> at runtime. Delphi inserts temporary string variable and conversion
>> (array of char -> string), but FPC treats the pointer literally.
MVC> Did you check the '@ returns typed pointer' setting in FPC ?
Oops... That was a false alarm - FPC compiler behaves the same way as
Delphi here. They both generate conversion code in {$T+} and do not
generate it in {$T-}.
So my sample appears to be legal only in {$T+}, which isn't a default.
What makes a difference is actually TStrings.SetTextStr implementation.
Delphi accesses the argument as null-terminated string, so it works perfectly
well even without conversion. FPC implementation treats argument as
AnsiString, accesses its Length field and eventually segfaults...
>> -
>> const
>> TestData: array[0..7] of Char = 'abc'#10'def'#0;
>>
>> procedure Test1;
>> var
>> sl: TStringList;
>> begin
>> sl := TStringList.Create;
>> sl.Text := string(@TestData[0]); // <- fails here
>> sl.Free;
>> end;
>> -
>>
>> Sample 2: This one compiles with Delphi (again, it inserts necessary
>> conversion Wide -> Ansi), but does not compile with FPC, neither in
>> objfpc nor in Delphi mode.
>>
>> -
>> function Test2: string;
>> var
>> buf: array[0..255] of char;
>> len: Integer;
>> begin
>> { (skipped) I read USB string descriptor into buf. After that,
>> buf[0] contains length of descriptor in bytes, buf[1] = 3,
>> and rest is filled with Unicode chars. Now I want to convert it into
>> ASCII...
>> }
>> len := Integer(buf[0]) shr 1;
>> SetString(result, PWideChar(@buf[2]), len-1);
>> end;
MVC> What is the error ?
It is 'Incompatible type for arg no.2: Got "PWideChar", expected
"PChar"'.
MVC> Michael.
MVC> ___
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MVC> http://lists.freepascal.org/mailman/listinfo/fpc-devel
--
Best regards,
Sergeimailto:[EMAIL PROTECTED]
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