Re: [fpc-pascal] SetLength warnings - request
Surely the point of a hint/warning is to point out a potential issue that the programmer may wish to correct. It should therefore be possible to change your code such a way that the hint/warning can be resolved so that it is no longer printed. This should not entail redundant or unnecessary code. The Wiki still indicates that SetLength only allocates the space, but it does not initialized the memory. Although this is probably incorrect for "array of string" to prevent memory leaks. I agree that SetLength should be a var parameter, as it can be used to reassign the size of a dynamic array, not just creating them. This must mean that the value passed is used, even for an assumably uninitialized array, so it must be initialized. Readability of the code is not enhanced by doing an unnecessary static initialization, you could do an equally ugly "pointer(var) := nil" Would it not be simpler to have the compiler initialize all dynamic array variables to nil, like for string variables, which should prevent the uninitialized warning/hint without requiring special treatment for handling the SetLength function. It does require that the compiler recognizes its own initialization of dynamic array variables. Derek On Sun, 30 Dec 2018 4:35 am Yuriy Sydorov On 29.12.2018 16:19, Benito van der Zander wrote: > > Hi, > > > >> even if there's closed issue > https://bugs.freepascal.org/view.php?id=34169 I would like to ask if it > can be reconsidered. > >> > >> The subject is that SetLength now gives warning: Variable "dynamic > array" of a managed type does not seem to be > >> initialized > >> > >> in 3.3.1 and 3.1.1 while it doesn't give any warning in stable 3.0.4 > >> > > > > seriously that is such a bullshit warning. > > > > SetLength is called to initialize the variable, of course the variable > is not initialized before. If it was initialized, > > we might not even need to call SetLength > > The current FPC trunk issues only a hint for the SetLength(). > > Yuriy. > ___ > fpc-pascal maillist - fpc-pascal@lists.freepascal.org > http://lists.freepascal.org/cgi-bin/mailman/listinfo/fpc-pascal ___ fpc-pascal maillist - fpc-pascal@lists.freepascal.org http://lists.freepascal.org/cgi-bin/mailman/listinfo/fpc-pascal
Re: [fpc-pascal] Question about System.Move()
re you'd > definitely need to use constref instead of const. > > And when you use IsManagedType, it does not distinguish standard strings >> with such weird managed types. >> > > You can additionally use GetTypeKind as well. Unlike TypeInfo it directly > returns the TTypeKind (which for this case is enough) and is considered > constant. > > And perhaps there could be a special attribute to mark which kind of >> moving is needed, e.g.. >> type [moveable] TA = record >> type [referencecounted] TA = record >> type [nonmoveable] TA = record >> > > No, thank you. > > Regards, > Sven > > ___ > fpc-pascal maillist - > fpc-pascal@lists.freepascal.orghttps://lists.freepascal.org/cgi-bin/mailman/listinfo/fpc-pascal > > ___ > fpc-pascal maillist - fpc-pascal@lists.freepascal.org > https://lists.freepascal.org/cgi-bin/mailman/listinfo/fpc-pascal > -- Derek Edson ___ fpc-pascal maillist - fpc-pascal@lists.freepascal.org https://lists.freepascal.org/cgi-bin/mailman/listinfo/fpc-pascal
Re: [fpc-pascal] Question about System.Move()
The reference count is only updated if the variable "A" was assigned to
another variable. However, if "A" was global, it may still be changed by a
second thread without changing its value.
program SwapTest;
uses
Classes, SysUtils;
type
{ MyThread }
MyThread = class(TThread)
protected
procedure Execute; override;
end;
type
PAnsiRec = ^TAnsiRec;
TAnsiRec = Record
CodePage: TSystemCodePage;
ElementSize : Word;
{$ifdef CPU64}
{ align fields }
Dummy : DWord;
{$endif CPU64}
Ref : SizeInt;
Len : SizeInt;
end;
var
AStr: string;
BStr: string;
LThread: TThread;
function SRefCount(P : Pointer) : integer;
begin
if P=Nil then
Result:=0
else
Result:=PAnsiRec(P-SizeOf(TAnsiRec))^.Ref;
end;
procedure stringSwap(var a, b: string);
var
t: string;
begin
writeln('RefCount of A before assign to T=', SRefCount(pointer(a)));
t := a;
writeln('RefCount of A after assign to T=', SRefCount(pointer(a)));
a := b;
b := t;
writeln('RefCount of A after at exit of stringSwap=',
SRefCount(pointer(a)));
writeln('RefCount of B after at exit of stringSwap=',
SRefCount(pointer(B)));
end;
{ MyThread }
procedure MyThread.Execute;
begin
AStr := '';
end;
begin
LThread := MyThread.Create(false);
writeln('Multi-threading=', IsMultiThread);
AStr := IntToStr(123);
UniqueString(AStr);
BStr := IntToHex(123, 3);
UniqueString(BStr);
writeln('AStr="', AStr, '", Reference count before call=',
SRefCount(pointer(AStr)));
writeln('BStr="', BStr, '", Reference count before call=',
SRefCount(pointer(BStr)));
stringSwap(AStr, BStr);
writeln('AStr="', AStr, '", Reference count after call=',
SRefCount(pointer(AStr)));
writeln('BStr="', BStr, '", Reference count after call=',
SRefCount(pointer(BStr)));
LThread.WaitFor;
LThread.Free;
end.
The output is dependent on the the timing of the two threads, but in this
case it occurred after the return of stringSwap, but you can still see the
affect of the variable being cleared by the second thread. This global
value could be assigned a new value, and that could also cause an issue as
the reference in your simplified code could still reference the old value
which may have been deleted.
Multi-threading=TRUE
AStr="123", Reference count before call=1
BStr="07B", Reference count before call=1
RefCount of A before assign to T=1
RefCount of A after assign to T=2
RefCount of A after on exit of stringSwap=1
RefCount of B after at exit of stringSwap=2
AStr="", Reference count after call=0
BStr="123", Reference count after call=1
Derek
On Sat, Jan 30, 2021 at 12:24 AM Benito van der Zander via fpc-pascal <
fpc-pascal@lists.freepascal.org> wrote:
> Hi,
>
>
> Should "A" have a reference count of 1, and it is assigned a new value on
> another thread, its reference count will decrease to zero and the string
> and its descriptor are both freed. The value of "A" will be set to nil.
>
>
> If the reference count is 1, there is no other thread involved.
> If there was another thread, there would be a reference in this thread and
> in the other thread, so the reference count would be at least 2
>
>
> It is exactly as thread safe as the unoptimized function. If the reference
> count was 1, the unoptimized function would not work either, since the
> thread swap might occur just before the first instruction, and the strings
> are freed before the function can do anyhting
>
>
> Bye,
> Benito
> On 28.01.21 08:08, Derek Edson via fpc-pascal wrote:
>
> Your simplified code would not be thread safe. A thread swap after the
> first instruction of
>
> mov (%rdi), %rax
>
> could potentially cause a problem. RAX (A) contains the pointer to the
> string descriptor, which includes the pointer to the actual string data and
> the reference count.
>
> Should "A" have a reference count of 1, and it is assigned a new value on
> another thread, its reference count will decrease to zero and the string
> and its descriptor are both freed. The value of "A" will be set to nil.
>
> RAX will not have been updated, so after
>
> mov %rax, (%rsi)
>
> "B" will be pointing to an invalid location. Its content is now dependent
> on memory reallocation.
>
> In this situation, changing "B" after the return from stringSwap procedure
> might again cause the string to be freed (assuming the memory was not
> reallocated), causing a double free error.
>
> Use of the internal procedures to increment the string reference count of
> both strings before your code and
Re: [fpc-pascal] Signing applications, how?
I have been using signtool for a number of years for apps built with Delphi and/or FPC. The question of whether you need a expensive CA based certification will depend on your IT department. Any certificate from any certification authority will work to sign an app, but it needs to be trusted by Windows for it to be used. Microsoft include a number of CA root certificates in the Windows distribution/updates, which may vary between Windows version. Use MMC, add/remove snapin, and select Certificates for the Local Computer. You can then see the supported root and intermediate certificates on your computer. Your IT department can add another CA root certificate by using group policy. This will also be push it to all computers on the network. https://docs.omnissa.com/bundle/Horizon8InstallUpgrade/page/AddtheRootCertificatetoTrustedRootCertificationAuthorities.html Derek On Sun, 11 Aug 2024, 1:33 am Bo Berglund via fpc-pascal, < fpc-pascal@lists.freepascal.org> wrote: > On Sat, 10 Aug 2024 13:32:12 +0200, Luca Olivetti via fpc-pascal > wrote: > > >El 10/8/24 a les 11:28, Jeppe Johansen via fpc-pascal ha escrit: > > > >> It's fairly straight-forward to use this on executables. You point it > at > >> the EXE and the code signing certificate you will use. > > > >I guess you'll have to get ($$$) a valid signing certificate too. > > > > Can I use LetsEncrypt certificates or must I cash out big to get a working > one? > > > -- > Bo Berglund > Developer in Sweden > > ___ > fpc-pascal maillist - fpc-pascal@lists.freepascal.org > https://lists.freepascal.org/cgi-bin/mailman/listinfo/fpc-pascal > ___ fpc-pascal maillist - fpc-pascal@lists.freepascal.org https://lists.freepascal.org/cgi-bin/mailman/listinfo/fpc-pascal
