[fpc-devel] TypeInfo RTTI / possible inconsistency

Post by Martin Frb via fpc-devel
I was looking at TypeInfo (based on 3.2.2rc)
line 632 unit TypInfo

....
              followed by
                  ResultType : ShortString     // for mkFunction,
mkClassFunction only
                  ResultTypeRef : PPTypeInfo; // for mkFunction,
mkClassFunction only
                  CC : TCallConv;
                  ParamTypeRefs : array[1..ParamCount] of PPTypeInfo;}
              );

To find out about alignment (for any target which needs alignment), I

And just to confirm, if anyone knows....

Those are indeed PPTypeInfo ? (even in 3.0?)

Since a lot of other TypeInfos are:
{$ifdef ver3_0}
{$define TypeInfoPtr := PTypeInfo}
{$else}
{$define TypeInfoPtr := PPTypeInfo}
{$endif}

Rtti.pas in 3.0.0 seems to tread them as PPTypeInfo. So that would
indicate they indeed are PPTypeInfo.
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Michael Van Canneyt via fpc-devel

2021-05-18 14:58:41 UTC

Post by Martin Frb via fpc-devel
I was looking at TypeInfo (based on 3.2.2rc)
line 632Â unit TypInfo

....
Â Â Â Â Â Â Â Â Â Â Â Â Â followed by
Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â ResultType : ShortStringÂ Â Â Â // for mkFunction,
mkClassFunction only
Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â ResultTypeRef : PPTypeInfo;Â // for mkFunction,
mkClassFunction only
Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â CC : TCallConv;
Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â ParamTypeRefs : array[1..ParamCount] of PPTypeInfo;}
Â Â Â Â Â Â Â Â Â Â Â Â Â );

To find out about alignment (for any target which needs alignment), I

And just to confirm, if anyone knows....
Those are indeed PPTypeInfo ? (even in 3.0?)
{$ifdef ver3_0}
{$define TypeInfoPtr := PTypeInfo}
{$else}
{$define TypeInfoPtr := PPTypeInfo}
{$endif}
Rtti.pas in 3.0.0 seems to tread them as PPTypeInfo. So that would
indicate they indeed are PPTypeInfo.

Yes. An additional level of indirection was introduced, for runtime package
support, if I recall correctly. This also makes it Delphi compatible.

But Sven can confirm this, I think he introduced the change.

Michael.

Martin Frb via fpc-devel

2021-05-18 15:33:41 UTC

Post by Martin Frb via fpc-devel
line 632 unit TypInfo

And just to confirm, if anyone knows....
Those are indeed PPTypeInfo ? (even in 3.0?)
{$ifdef ver3_0}
{$define TypeInfoPtr := PTypeInfo}
{$else}
{$define TypeInfoPtr := PPTypeInfo}
{$endif}

I looked at ncgrtti in the compiler.

It looks like ResultTypeRef and ParamTypeRef are TypeInfoPtr and not
PPTypeInfo

Post by Martin Frb via fpc-devel
Rtti.pas in 3.0.0 seems to tread them as PPTypeInfo. So that would
indicate they indeed are PPTypeInfo.

3.0 does not have rtti.pp => I was in the wrong directory
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Sven Barth via fpc-devel

2021-05-19 20:21:34 UTC

Post by Martin Frb via fpc-devel
line 632 unit TypInfo

And just to confirm, if anyone knows....
Those are indeed PPTypeInfo ? (even in 3.0?)
{$ifdef ver3_0}
{$define TypeInfoPtr := PTypeInfo}
{$else}
{$define TypeInfoPtr := PPTypeInfo}
{$endif}

I looked at ncgrtti in the compiler.
It looks like ResultTypeRef and ParamTypeRef are TypeInfoPtr and not
PPTypeInfo

Right, sorry, in 3.0 they're indeed PTypeInfo. In 3.2.0 they were
changed ot indirect references.

Regards,
Sven
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Sven Barth via fpc-devel

2021-05-19 20:13:35 UTC

Post by Martin Frb via fpc-devel
I was looking at TypeInfo (based on 3.2.2rc)
line 632 unit TypInfo

To find out about alignment (for any target which needs alignment), I

They were only introduced in 3.0.0, thus they were introduced as
PPTypeInfo right away as that is required for dynamic packages on
Windows to work correctly (as Michael mentioned).

Regards,
Sven
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Sven Barth via fpc-devel

2021-05-19 20:10:26 UTC

Post by Martin Frb via fpc-devel
I was looking at TypeInfo (based on 3.2.2rc)
line 632 unit TypInfo

To find out about alignment (for any target which needs alignment), I
fpc_3.2.2\source\tests\webtbs\tw12038.pp
line 194 procedure DisplayDetails(Informations : TPropInfo;
const expectedresult: ansistring);
appears to access the data (except for the ParamTypeRefs array)
The testcase does not seem to make any adjustments for alignment.

It does at line 285.

Post by Martin Frb via fpc-devel
fpc_3.2.2\source\packages\rtl-objpas\src\inc\rtti.pp
   line 3341    TRttiMethodType.GetParameters
also appears to access the same typeinfo.
It makes alignments in 3 different places
TParamFlags;   in the ParamList
   ptr := AlignToPtr(PByte(ptr) + ptr^ + SizeOf(Byte));    // ResultTypeRef
   paramtypes := PPPTypeInfo(AlignTypeData(ptr));     // ParamTypeRefs
Which is correct?
Or do they access different structures?

They are for different parts of the structure, cause they have different
alignment requirements (e.g. the param names and flags are aligned to
the TParamFlags (which is 2 Byte) while the ResultType is aligned to a
pointer. Though right now I don't know why the last one uses
AlignTypeData which would align to the QWord fields instead of Pointer
ones...

Post by Martin Frb via fpc-devel
FPC_REQUIRES_PROPER_ALIGNMENT
does not seem to be listed on
https://www.freepascal.org/docs-html/prog/progap7.html

There are a few from TOption.TargetOptions (in options.pas) that are not
yet documented.

Post by Martin Frb via fpc-devel
TypInfo line 1461
in Procedure GetPropInfos(TypeInfo : PTypeInfo;PropList : PPropList);
Why call aligntoptr twice?
The TypeCast in between does not change the alignment. (all the math
is done within the innermost call)

That one is already fixed in trunk.

Regards,
Sven
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Martin Frb via fpc-devel

2021-05-19 20:42:17 UTC

Post by Martin Frb via fpc-devel
I was looking at TypeInfo (based on 3.2.2rc)
.....
fpc_3.2.2\source\tests\webtbs\tw12038.pp
line 194 procedure DisplayDetails(Informations : TPropInfo;
const expectedresult: ansistring);
appears to access the data (except for the ParamTypeRefs array)
The testcase does not seem to make any adjustments for alignment.

It does at line 285.

Ok, now I looked at trunk (should have done before).
In 3.2.2rc the align is not present.

Post by Martin Frb via fpc-devel
It makes alignments in 3 different places
TParamFlags;   in the ParamList
   ptr := AlignToPtr(PByte(ptr) + ptr^ + SizeOf(Byte));    // ResultTypeRef
   paramtypes := PPPTypeInfo(AlignTypeData(ptr));     // ParamTypeRefs
Which is correct?
Or do they access different structures?

They are for different parts of the structure,

Misunderstanding. Not "which of the 3", but "testcase or unit" =>
Solved, the latter (in trunk: both)

Anyway thanks for the feedback.

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Sven Barth via fpc-devel

2021-05-19 21:31:41 UTC

It does at line 285.

Ok, now I looked at trunk (should have done before).
In 3.2.2rc the align is not present.

That is because the alignment requirements changed in trunks with the
addition of the attributes (though I'm not entirely happy with that yet).