[fpc-devel] RTTI's GetPropValue returns corrupt Boolean value
Hi,
I've included a program that shows the problem. I'm using FPC 2.2.0
under Linux on a Intel P4.
I've got a function PropertyMatch() which returns true or false if a
given property matches a specified value. All very simple.
But for some strange reason TypInfo.GetPropValue returns a boolean
which seems to test ok using VarIsType(), but if I cast it as a
boolean variant using VarIsType() just to be sure, the application
throws the error show below.
Any ideas how to resolve this issue? Is it a FPC bug? This same code
works perfectly with Delphi 7-2007.
[EMAIL PROTECTED]:rtti_bug$ ./project1
Test 1 passed. Integer property matched.
Test 2 passed. String property matched.
An unhandled exception occurred at $0807F54D :
EVariantTypeCastError : Could not convert variant of type (Int64) into
type (Boolean)
$0807F54D
$0807C5EB
$0807D139
$08048467 main, line 85 of project1.lpr
[ Backtrace ]--
(gdb) break fpc_raiseexception
Breakpoint 1 at 0x8054886
(gdb) run
Starting program: /home/graemeg/programming/tests/rtti_bug/project1
Test 1 passed. Integer property matched.
Test 2 passed. String property matched.
Breakpoint 1, 0x08054886 in fpc_raiseexception ()
(gdb) bt
#0 0x08054886 in fpc_raiseexception ()
#1 0x0807f539 in VARIANTS_VARCASTERROR$WORD$WORD ()
#2 0x0807c5cb in VARIANTS_SYSVARCAST$VARIANT$VARIANT$LONGINT ()
#3 0x0807d119 in VARIANTS_VARASTYPE$VARIANT$WORD$$VARIANT ()
#4 0xbfa82934 in ?? ()
#5 0xbfa828d4 in ?? ()
#6 0x08048189 in PROPERTYMATCH (AOBJECT=0xb7f4a100,
PROPNAME=0x80a1ab4, PROPVALUE=void)
at project1.lpr:41
#7 0x08048467 in main () at project1.lpr:82
- end
-[ the program code ]--
program project1;
{$mode objfpc}{$H+}
uses
Classes, typinfo, variants;
type
{$M+}
TMyObject = class(TObject)
private
FBoolProp: Boolean;
FIntProp: Integer;
FStrProp: string;
published
property IntProp: Integer read FIntProp write FIntProp;
property BoolProp: Boolean read FBoolProp write FBoolProp;
property StrProp: string read FStrProp write FStrProp;
end;
{$M-}
// This does a test to see if the property PropName's value
// matches PropValue.
function PropertyMatch(AObject: TObject; PropName: string;
PropValue: variant): boolean;
var
lSearch, lItem: variant;
lVarType: TVarType;
lPropInfo: PPropInfo;
begin
lSearch := PropValue;
lItem := TypInfo.GetPropValue(AObject, PropName);
lVarType := VarType(lItem);
// Just to be sure that I'm comparing the SAME kind of values
if VarIsType(PropValue, varBoolean) then
begin
lItem := VarAsType(lItem, varBoolean); // === EVariantTypeCastError
// lItem := VarAsType(True, varBoolean); // this passes if we
force boolean
end
else
begin
lSearch := VarAsType(lSearch, lVarType);
lItem := VarAsType(lItem, lVarType);
end;
result := (lSearch = lItem);
end;
var
obj: TMyObject;
lBool: Boolean;
begin
obj := TMyObject.Create;
try
obj.IntProp := 123;
obj.BoolProp := True;
obj.StrProp := 'abcd';
// Testing a Integer property
if PropertyMatch(obj, 'IntProp', 123) then
writeln('Test 1 passed. Integer property matched.')
else
writeln('Test 1 failed');
// Testing a String property
if PropertyMatch(obj, 'StrProp', 'abcd') then
writeln('Test 2 passed. String property matched.')
else
writeln('Test 2 failed');
// Testing a Boolean property
// We can also try it with a typed variable
//lBool := True;
//if PropertyMatch(obj, 'BoolProp', lBool) then
if PropertyMatch(obj, 'BoolProp', True) then
writeln('Test 3 passed. Boolean property matched.')
else
writeln('Test 3 failed');
finally
obj.Free;
end;
end.
- end
Regards,
- Graeme -
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Re: [fpc-devel] RTTI's GetPropValue returns corrupt Boolean value
On Tue, 20 Nov 2007, Graeme Geldenhuys wrote: Hi, I've included a program that shows the problem. I'm using FPC 2.2.0 under Linux on a Intel P4. I've got a function PropertyMatch() which returns true or false if a given property matches a specified value. All very simple. But for some strange reason TypInfo.GetPropValue returns a boolean which seems to test ok using VarIsType(), but if I cast it as a boolean variant using VarIsType() just to be sure, the application throws the error show below. Any ideas how to resolve this issue? Is it a FPC bug? This same code works perfectly with Delphi 7-2007. It depends on the choices made when converting variants to native types or vice versa (even more difficult when it occurs in an expression). It's hard to say whether this is an actual error or an incompatibility. Looking at the code and the error, I'd say that somewhere along the line fpc converted a variant to int64 instead of to an integer as delphi seems to do. It's just one of these reasons why it is IMHO better not to use Variants: things happen behind the scenes that are not very clear (and that are not documented ) Michael. ___ fpc-devel maillist - fpc-devel@lists.freepascal.org http://lists.freepascal.org/mailman/listinfo/fpc-devel
Re: [fpc-devel] RTTI's GetPropValue returns corrupt Boolean value
On 20/11/2007, Michael Van Canneyt [EMAIL PROTECTED] wrote: It's hard to say whether this is an actual error or an incompatibility. Well this 'error' has been around in tiOPF since I ported it to FPC (about 3 years) and now it's really bugging me. :) Looking at the code and the error, I'd say that somewhere along the line fpc converted a variant to int64 instead of to an integer as delphi seems to do. No idea, I may not look at the Delphi code remember! ;-) It's just one of these reasons why it is IMHO better not to use Variants: things happen behind the scenes that are not very clear (and that are not documented ) Fair enough. I'm not a fan of Variants either, but how else would I write the PropertyMatch() function then? Yes I could do some extra tests and use GetStrProp, GetIntProp, GetFloatProp etc. but there isn't a GetBooleanProp(). I would imagine I need to use the GetOrdProp for Boolean, but looking at the function definition for GetOrdProp, it outputs a Int64 which is probably what gave me the error in the first place (casting Bool to Int64 or vice-versa). Note that the PropertyMatch() function I have in the example is a scaled down version (just to highlight the issue) of the full one in tiOPF. I need to handle all property types. Regards, - Graeme - ___ fpGUI - a cross-platform Free Pascal GUI toolkit http://opensoft.homeip.net/fpgui/ ___ fpc-devel maillist - fpc-devel@lists.freepascal.org http://lists.freepascal.org/mailman/listinfo/fpc-devel
Re: [fpc-devel] RTTI's GetPropValue returns corrupt Boolean value
On Tue, 20 Nov 2007, Graeme Geldenhuys wrote: On 20/11/2007, Michael Van Canneyt [EMAIL PROTECTED] wrote: It's hard to say whether this is an actual error or an incompatibility. Well this 'error' has been around in tiOPF since I ported it to FPC (about 3 years) and now it's really bugging me. :) Looking at the code and the error, I'd say that somewhere along the line fpc converted a variant to int64 instead of to an integer as delphi seems to do. No idea, I may not look at the Delphi code remember! ;-) Point scored :-) It's just one of these reasons why it is IMHO better not to use Variants: things happen behind the scenes that are not very clear (and that are not documented ) Fair enough. I'm not a fan of Variants either, but how else would I write the PropertyMatch() function then? Yes I could do some extra tests and use GetStrProp, GetIntProp, GetFloatProp etc. This is IMHO the only correct way. but there isn't a GetBooleanProp(). I would imagine I need to use the GetOrdProp for Boolean, but looking at the function definition for GetOrdProp, it outputs a Int64 which is probably what gave me the error in the first place (casting Bool to Int64 or vice-versa). It probably retuns an int(64), and when it's converted to variant - I don't know. I'd have to look at the code. Note that the PropertyMatch() function I have in the example is a scaled down version (just to highlight the issue) of the full one in tiOPF. I need to handle all property types. This is exactly where the easy access to RTTI would come in handy, and which is why I would like to have it. If you want we can always discuss in private the design of such an easy-acces method. Michael. ___ fpc-devel maillist - fpc-devel@lists.freepascal.org http://lists.freepascal.org/mailman/listinfo/fpc-devel
Re: [fpc-devel] RTTI's GetPropValue returns corrupt Boolean value
On 20/11/2007, Michael Van Canneyt [EMAIL PROTECTED] wrote: Fair enough. I'm not a fan of Variants either, but how else would I write the PropertyMatch() function then? Yes I could do some extra tests and use GetStrProp, GetIntProp, GetFloatProp etc. This is IMHO the only correct way. I've extended the PropertyMatch() function to test for tkBool types (no variants) and do a writeln when it finds it. That parts seems to work fine. It probably retuns an int(64), and when it's converted to variant - I don't know. I'd have to look at the code. That would be great. I'm on my way home now, but will continue looking at the code tomorrow. More eyeballs on the code is always better. This is exactly where the easy access to RTTI would come in handy, and which is why I would like to have it. If you want we can always discuss in private the design of such an easy-acces method. I've created a tiRTTI.pas unit in tiOPF, but it's simply wrappers for calling many other functions. It makes it a bit easier to use RTTI though. But yes I wouldn't mind discussion an 'easy-access' method for RTTI. Regards, - Graeme - ___ fpGUI - a cross-platform Free Pascal GUI toolkit http://opensoft.homeip.net/fpgui/ ___ fpc-devel maillist - fpc-devel@lists.freepascal.org http://lists.freepascal.org/mailman/listinfo/fpc-devel
Re: [fpc-devel] RTTI's GetPropValue returns corrupt Boolean value
On 20/11/2007, Graeme Geldenhuys [EMAIL PROTECTED] wrote:
I've extended the PropertyMatch() function to test for tkBool types
(no variants) and do a writeln when it finds it. That parts seems to
work fine.
Here is the debug code I added to PropertyMatch() which successfully
compare the results, but I have to explicitly cast GetOrdProp to a
Boolean. Is that normal???
PropInfo := GetPropInfo(AObject.ClassType, PropName);
if tiGetTypeInfo(PropInfo)^.Kind = tkBool then
begin
writeln('Found rtti bool type');
lbool := Boolean(GetOrdProp(AObject, PropName));
if lSearch = lbool then
writeln('Comparison was a success');
end;
Regards,
- Graeme -
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Re: [fpc-devel] RTTI's GetPropValue returns corrupt Boolean value
On Tue, 20 Nov 2007, Graeme Geldenhuys wrote: On 20/11/2007, Graeme Geldenhuys [EMAIL PROTECTED] wrote: I've extended the PropertyMatch() function to test for tkBool types (no variants) and do a writeln when it finds it. That parts seems to work fine. Here is the debug code I added to PropertyMatch() which successfully compare the results, but I have to explicitly cast GetOrdProp to a Boolean. Is that normal??? Yes. Michael. ___ fpc-devel maillist - fpc-devel@lists.freepascal.org http://lists.freepascal.org/mailman/listinfo/fpc-devel
Re: [fpc-devel] RTTI's GetPropValue returns corrupt Boolean value
Graeme Geldenhuys wrote:
On 20/11/2007, Graeme Geldenhuys [EMAIL PROTECTED] wrote:
I've extended the PropertyMatch() function to test for tkBool types
(no variants) and do a writeln when it finds it. That parts seems to
work fine.
Here is the debug code I added to PropertyMatch() which successfully
compare the results, but I have to explicitly cast GetOrdProp to a
Boolean. Is that normal???
PropInfo := GetPropInfo(AObject.ClassType, PropName);
if tiGetTypeInfo(PropInfo)^.Kind = tkBool then
begin
writeln('Found rtti bool type');
lbool := Boolean(GetOrdProp(AObject, PropName));
if lSearch = lbool then
writeln('Comparison was a success');
end;
Sounds familiar. Here I have:
if UsePublishedGetter then
Result := Boolean(GetOrdProp(Owner, Metadata.Name))
else
Result := Value;
--
Joao Morais
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