[fpc-devel] Error compiling trunk on FreeBSD
Hi, I'm trying to compile the r17057 on FreeBSD x86_64 and I'm getting this error: fpc/rtl/units/x86_64-freebsd/cpu.s:40: Error: no such instruction: `cmpxchg16b (%r8) Any hint? ___ fpc-devel maillist - fpc-devel@lists.freepascal.org http://lists.freepascal.org/mailman/listinfo/fpc-devel
[fpc-devel] Error compiling trunk on FreeBSD
Hi, I'm trying to compile the r17057 on FreeBSD x86_64 and I'm getting this error: fpc/rtl/units/x86_64-freebsd/cpu.s:40: Error: no such instruction: `cmpxchg16b (%r8) Any hint? ___ fpc-devel maillist - fpc-devel@lists.freepascal.org http://lists.freepascal.org/mailman/listinfo/fpc-devel
[fpc-devel] GetMem(SomePointer, 0) nil
Hello, FPC developers' list. I noticed today that if I want to allocate 0 bytes I get not a nil but a valid pointer. Why? This is incompatible with delphi. And I suppose cause crashes and memory leaks not only in my delphi code which I'm porting to FPC/Lazarus. -- Best regards, Paul Ishenin. ___ fpc-devel maillist - fpc-devel@lists.freepascal.org http://lists.freepascal.org/mailman/listinfo/fpc-devel
Re: [fpc-devel] GetMem(SomePointer, 0) nil
On Tue, 1 Mar 2011, Paul Ishenin wrote: Hello, FPC developers' list. I noticed today that if I want to allocate 0 bytes I get not a nil but a valid pointer. Why? This is incompatible with delphi. And I suppose cause crashes and memory leaks not only in my delphi code which I'm porting to FPC/Lazarus. Well, in all these years, you're the first to notice, so I'm not inclined to think it is a big problem. Does it say in the Delphi docs that Nil is returned if Size=0 ? Michael. ___ fpc-devel maillist - fpc-devel@lists.freepascal.org http://lists.freepascal.org/mailman/listinfo/fpc-devel
Re: [fpc-devel] GetMem(SomePointer, 0) nil
On Tue, Mar 1, 2011 at 1:20 PM, Michael Van Canneyt mich...@freepascal.org wrote: Does it say in the Delphi docs that Nil is returned if Size=0 ? Not in the online ones: http://docwiki.embarcadero.com/VCL/en/System.GetMem -- Felipe Monteiro de Carvalho ___ fpc-devel maillist - fpc-devel@lists.freepascal.org http://lists.freepascal.org/mailman/listinfo/fpc-devel
Re: [fpc-devel] GetMem(SomePointer, 0) nil
On 01 Mar 2011, at 07:32, Paul Ishenin wrote: I noticed today that if I want to allocate 0 bytes I get not a nil but a valid pointer. Why? The current code that causes this comes from this (cvs) revision: revision 1.16 date: 1999-09-17 19:14:12 +0200; author: peter; state: Exp; lines: +284 -966; + new heap manager supporting delphi freemem(pointer) I guess the reason was to be able to a) give a run time error if someone tries to do freemem(nil) b) nevertheless allow freeing all pointers that have been allocated using getmem() (even if the size was 0 bytes), for backwards compatibility with FPC code from before that revision (FPC also returned a non-nil pointer in that case) This is incompatible with delphi. If it is changed, it will also require changes in cmem (and probably also in heaptrc), because at least on Mac OS X libc also returns a valid pointer for malloc(0). And I suppose cause crashes and memory leaks not only in my delphi code which I'm porting to FPC/Lazarus. That sounds very much like badly written code. Jonas ___ fpc-devel maillist - fpc-devel@lists.freepascal.org http://lists.freepascal.org/mailman/listinfo/fpc-devel
Re: [fpc-devel] GetMem(SomePointer, 0) nil
01.03.2011 19:20, Michael Van Canneyt wrote: Well, in all these years, you're the first to notice, so I'm not inclined to think it is a big problem. Does it say in the Delphi docs that Nil is returned if Size=0 ? I don't know but a simple test shows this. Best regards, Paul Ishenin ___ fpc-devel maillist - fpc-devel@lists.freepascal.org http://lists.freepascal.org/mailman/listinfo/fpc-devel
Re: [fpc-devel] GetMem(SomePointer, 0) nil
01.03.2011 19:29, Jonas Maebe wrote: That sounds very much like badly written code. For simplicity we had the next code: GetMem(SomeArray, Count * SizeOf(ArrayCell)) if SomeArray nil then DoSomeLogic; Best regards, Paul Ishenin ___ fpc-devel maillist - fpc-devel@lists.freepascal.org http://lists.freepascal.org/mailman/listinfo/fpc-devel
Re: [fpc-devel] GetMem(SomePointer, 0) nil
Jonas Maebe пишет: On 01 Mar 2011, at 07:32, Paul Ishenin wrote: I noticed today that if I want to allocate 0 bytes I get not a nil but a valid pointer. Why? The current code that causes this comes from this (cvs) revision: revision 1.16 date: 1999-09-17 19:14:12 +0200; author: peter; state: Exp; lines: +284 -966; + new heap manager supporting delphi freemem(pointer) I guess the reason was to be able to a) give a run time error if someone tries to do freemem(nil) Delphi allows freemem(nil) without error, consistent with TObject.Free b) nevertheless allow freeing all pointers that have been allocated using getmem() (even if the size was 0 bytes), for backwards compatibility with FPC code from before that revision (FPC also returned a non-nil pointer in that case) This is incompatible with delphi. I remember a discussion some time ago, the conclusion was it's compatible with TP rather than with Delphi. If it is changed, it will also require changes in cmem (and probably also in heaptrc), because at least on Mac OS X libc also returns a valid pointer for malloc(0). Not necessary, if we have only one GetMem function (currently we have several - getmem, fpc_getmem, getmemory and maybe something else, each calling MemoryManager independently) and write it like this: if size=0 then result := nil else result := MemoryManager.GetMem(size); And I suppose cause crashes and memory leaks not only in my delphi code which I'm porting to FPC/Lazarus. That sounds very much like badly written code. Fully agree. Sergei ___ fpc-devel maillist - fpc-devel@lists.freepascal.org http://lists.freepascal.org/mailman/listinfo/fpc-devel
Re: [fpc-devel] GetMem(SomePointer, 0) nil
Paul Ishenin schrieb: I noticed today that if I want to allocate 0 bytes I get not a nil but a valid pointer. Why? This will allow for a following Realloc. Even in Delphi the behaviour may be subject to the installed memory manager. DoDi ___ fpc-devel maillist - fpc-devel@lists.freepascal.org http://lists.freepascal.org/mailman/listinfo/fpc-devel
Re: [fpc-devel] GetMem(SomePointer, 0) nil
On 01 Mar 2011, at 15:25, Sergei Gorelkin wrote: Jonas Maebe пишет: a) give a run time error if someone tries to do freemem(nil) Delphi allows freemem(nil) without error, consistent with TObject.Free I don't think TObject.Free and freemem are really comparable. TObject.Free is much more high level. I remember a discussion some time ago, the conclusion was it's compatible with TP rather than with Delphi. TP also returns nil for getmem(0) (and allows freemem(nil,0) -- TP doesn't have a freemem() function without a separate size parameter). I guess it's one of the ways in which the FPC version was intended to be cleaner than the TP and Delphi versions of the same functions (and since they're RTL functions, they cannot simply be changed based on the compilation mode of the current unit). Since it's also consistent with how other memory allocators work (e.g., the libc ones), I don't think that was a bad decision. If it is changed, it will also require changes in cmem (and probably also in heaptrc), because at least on Mac OS X libc also returns a valid pointer for malloc(0). Not necessary, if we have only one GetMem function It's true, that way it could also be changed. Jonas___ fpc-devel maillist - fpc-devel@lists.freepascal.org http://lists.freepascal.org/mailman/listinfo/fpc-devel
Re: [fpc-devel] GetMem(SomePointer, 0) nil
Paul Ishenin wrote: 01.03.2011 19:29, Jonas Maebe wrote: That sounds very much like badly written code. For simplicity we had the next code: GetMem(SomeArray, Count * SizeOf(ArrayCell)) if SomeArray nil then DoSomeLogic; DoSomeLogic ... with a Count = 0, right? or was Sizeof(...) = 0? :-) Micha ___ fpc-devel maillist - fpc-devel@lists.freepascal.org http://lists.freepascal.org/mailman/listinfo/fpc-devel
Re: [fpc-devel] GetMem(SomePointer, 0) nil
On Tue, 01 Mar 2011 22:19:38 +0100, Micha Nelissen mi...@neli.hopto.org wrote: Paul Ishenin wrote: 01.03.2011 19:29, Jonas Maebe wrote: That sounds very much like badly written code. For simplicity we had the next code: GetMem(SomeArray, Count * SizeOf(ArrayCell)) if SomeArray nil then DoSomeLogic; DoSomeLogic ... with a Count = 0, right? or was Sizeof(...) = 0? :-) What I wonder is, if GetMem returns a non-NIL, valid pointer for a request of zero bytes of memory, where does this pointer actually point to? ;) Vinzent. ___ fpc-devel maillist - fpc-devel@lists.freepascal.org http://lists.freepascal.org/mailman/listinfo/fpc-devel
Re: [fpc-devel] GetMem(SomePointer, 0) nil
On 01 Mar 2011, at 22:58, Vinzent Höfler wrote: What I wonder is, if GetMem returns a non-NIL, valid pointer for a request of zero bytes of memory, where does this pointer actually point to? ;) To a small, non-zero sized memory block. Jonas___ fpc-devel maillist - fpc-devel@lists.freepascal.org http://lists.freepascal.org/mailman/listinfo/fpc-devel
Re: [fpc-devel] Error compiling trunk on FreeBSD
On Tue, Mar 1, 2011 at 03:07, Leonardo M. Ramé martinr...@yahoo.com wrote: Hi, I'm trying to compile the r17057 on FreeBSD x86_64 and I'm getting this error: fpc/rtl/units/x86_64-freebsd/cpu.s:40: Error: no such instruction: `cmpxchg16b (%r8) Any hint? It seems you should upgrade your assembler/binutils? (No idea how to to do that on BSD). -- Alexander S. Klenin ___ fpc-devel maillist - fpc-devel@lists.freepascal.org http://lists.freepascal.org/mailman/listinfo/fpc-devel
Re: [fpc-devel] GetMem(SomePointer, 0) nil
On Wed, Mar 2, 2011 at 01:01, Hans-Peter Diettrich drdiettri...@aol.com wrote:
Paul Ishenin schrieb:
I noticed today that if I want to allocate 0 bytes I get not a nil but a
valid pointer. Why?
This will allow for a following Realloc.
Even in Delphi the behaviour may be subject to the installed memory manager.
Maybe {$mode delphi} should by default install dephi-compatible memory manager?
--
Alexander S. Klenin
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Re: [fpc-devel] GetMem(SomePointer, 0) nil
02.03.2011 7:23, Alexander Klenin wrote:
Maybe {$mode delphi} should by default install dephi-compatible memory
manager?
No. Different units cannot install different memory managers. This will
be even more dangerous than to be just incompatible with delphi.
Best regards,
Paul Ishenin
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Re: [fpc-devel] GetMem(SomePointer, 0) nil
On Wed, Mar 2, 2011 at 10:28, Paul Ishenin webpi...@mail.ru wrote:
02.03.2011 7:23, Alexander Klenin wrote:
Maybe {$mode delphi} should by default install dephi-compatible memory
manager?
No. Different units cannot install different memory managers. This will be
even more dangerous than to be just incompatible with delphi.
Indeed. I was not thinking. But surely you can install such a manager
for your project?
--
Alexander S. Klenin
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Re: [fpc-devel] GetMem(SomePointer, 0) nil
02.03.2011 5:24, Jonas Maebe wrote: To a small, non-zero sized memory block. Memory allocation is time cost. Either user code should compare that for the zero bytes it should not call a GetMem or GetMem can compare this for user. Since GetMem already has a condition which compares for 0 - it is be the best place for doing this. Therefore FPC GetMem is not only incompatible with delphi GetMem but also can slowdown an application if it relies on GetMem logic and does not have a special checks for Count = 0 case. Best regards, Paul Ishenin ___ fpc-devel maillist - fpc-devel@lists.freepascal.org http://lists.freepascal.org/mailman/listinfo/fpc-devel
