Re: [fpc-devel] Type Compatibility: dynarray <=> Pointer
That compiles as well because Pointer(0) is converted by the compiler to nil. There is even a dedicated warning for this when used in a const: http://docwiki.embarcadero.com/RADStudio/Tokyo/en/W1013_Constant_0_converted_to_NIL_(Delphi) Am 17.04.2018 um 13:24 schrieb Martok: Am 17.04.2018 um 11:52 schrieb Stefan Glienke: FWIW this has been changed in Delphi 10.2 and does not compile anymore but gives: E2010 Incompatible types: 'Dynamic array' and 'Pointer' That is what I would have expected. Could you please test what the following does in D10.2? var arr: array of byte; begin arr:= Pointer(0); end. What I'd like to know: do they check the "nil" literal, or pointers of value nil? --- Diese E-Mail wurde von Avast Antivirus-Software auf Viren geprüft. https://www.avast.com/antivirus ___ fpc-devel maillist - fpc-devel@lists.freepascal.org http://lists.freepascal.org/cgi-bin/mailman/listinfo/fpc-devel
Re: [fpc-devel] Type Compatibility: dynarray <=> Pointer
Am 17.04.2018 um 11:52 schrieb Stefan Glienke: > FWIW this has been changed in Delphi 10.2 and does not compile anymore but > gives: > E2010 Incompatible types: 'Dynamic array' and 'Pointer' That is what I would have expected. Could you please test what the following does in D10.2? var arr: array of byte; begin arr:= Pointer(0); end. What I'd like to know: do they check the "nil" literal, or pointers of value nil? -- Regards, Martok ___ fpc-devel maillist - fpc-devel@lists.freepascal.org http://lists.freepascal.org/cgi-bin/mailman/listinfo/fpc-devel
Re: [fpc-devel] Type Compatibility: dynarray <=> Pointer
FWIW this has been changed in Delphi 10.2 and does not compile anymore but gives: E2010 Incompatible types: 'Dynamic array' and 'Pointer' > On 16 April 2018 at 17:21 Martok wrote: > > > Hi all, > > I have started debugging 0031215, and discovered something slightly unrelated, > but odd. I hope someone can clear that up. > While testing, I found out that the following compiles, and becomes a call to > fpc_dynarray_assign: > > var > arr: array of byte; > begin > arr:= Pointer(42); > end. > > This eventually happens because of the conversion case arraydef<=pointerdef in > defcmp.pas:1151, where a comment says: "nil and voidpointers are compatible > with > dyn. arrays". This comment was there since the very first SVN import. > > My question: why *are* voidpointers assignment compatible to dynarrays? It > does > seem to be Delphi compatible, but I couldn't find any mention in either > documentation that this is possible - only the reserved/constant "nil" is > compatible, and handled elsewhere. > > -- > Regards, > Martok > > > ___ > fpc-devel maillist - fpc-devel@lists.freepascal.org > http://lists.freepascal.org/cgi-bin/mailman/listinfo/fpc-devel ___ fpc-devel maillist - fpc-devel@lists.freepascal.org http://lists.freepascal.org/cgi-bin/mailman/listinfo/fpc-devel
Re: [fpc-devel] Type Compatibility: dynarray <=> Pointer
Am 17.04.2018 um 01:51 schrieb Thorsten Engler: > And the nil assignment variant is pretty much ubiquitous in any code > involving dynamic arrays that I'm aware of. Yes. I know ;-) >> only the reserved/constant "nil" is compatible, and handled elsewhere I asked specifically about assigning arbitrary untyped pointers. ___ fpc-devel maillist - fpc-devel@lists.freepascal.org http://lists.freepascal.org/cgi-bin/mailman/listinfo/fpc-devel
Re: [fpc-devel] Type Compatibility: dynarray <=> Pointer
A zero length dynamic array is represented by a nil pointer instead of a pointer to the heap with the information that the length of the array is 0. arr := nil; is equivalent to: SetLength(arr, 0); And the nil assignment variant is pretty much ubiquitous in any code involving dynamic arrays that I'm aware of. > -Original Message- > From: fpc-devel On Behalf > Of Martok > Sent: Tuesday, 17 April 2018 01:21 > To: fpc-devel@lists.freepascal.org > Subject: [fpc-devel] Type Compatibility: dynarray <=> Pointer > > Hi all, > > I have started debugging 0031215, and discovered something slightly > unrelated, but odd. I hope someone can clear that up. > While testing, I found out that the following compiles, and becomes > a call to > fpc_dynarray_assign: > > var > arr: array of byte; > begin > arr:= Pointer(42); > end. > > This eventually happens because of the conversion case > arraydef<=pointerdef in defcmp.pas:1151, where a comment says: "nil > and voidpointers are compatible with dyn. arrays". This comment was > there since the very first SVN import. > > My question: why *are* voidpointers assignment compatible to > dynarrays? It does seem to be Delphi compatible, but I couldn't > find any mention in either documentation that this is possible - > only the reserved/constant "nil" is compatible, and handled > elsewhere. > > -- > Regards, > Martok > > > ___ > fpc-devel maillist - fpc-devel@lists.freepascal.org > http://lists.freepascal.org/cgi-bin/mailman/listinfo/fpc-devel ___ fpc-devel maillist - fpc-devel@lists.freepascal.org http://lists.freepascal.org/cgi-bin/mailman/listinfo/fpc-devel
