Hi everyone,

So I reported this morning that Lazarus no longer builds as of r43826.  Ondrej was quick to update the Lazarus sources to allow it to build again and marking the issue as fixed, but the underlying regression in the Free Pascal Compiler still exists.

Basically, the compiler failed on constructs like this

   with
InputHistories.HistoryLists.GetList('BuildExecBefore',true,rltCaseSensitive)
do begin
     Assign(ExecuteBeforeCommandComboBox.Items);
     Push(Options.ExecuteBefore.Command);
   end;

The fix was to replace it with the following
(ide/frames/compiler_compilation_options.pas - line 394):

   HL :=
InputHistories.HistoryLists.GetList('BuildExecBefore',true,rltCaseSensitive);
   HL.Assign(ExecuteBeforeCommandComboBox.Items);
   HL.Push(Options.ExecuteBefore.Command);

Given the "illegal qualifier" errors that appeared, I'm guessing the issue is that "Options" is also a property of the THistoryList class as well as a local variable.  Technically speaking though, this is a regression unless it's to be documented (and hence break backward compatibility) that if you have a property and a local variable of the same name, the property takes precedence.

Gareth aka. Kit

P.S. The issue can be found here:
https://bugs.freepascal.org/view.php?id=36507

Nonsense.

That would mean that adding any new property in any object is a breaking change because the same name can be used in any possible with-statement at any place in any program or any local variable etc.

Short: every new property introduces a risk of clashes.

Ondrej

This was not a new property or a recent change to the Lazarus sources though.  I was using an old revision of Lazarus to test optimisations on, and had been doing fine with it until I discovered last night that it would no longer build.  Updating to the latest repository didn't change the file in question. Something in the compiler was changed recently that caused it to break when it was able to handle the clash before.

Gareth aka. Kit

J. Gareth Moreton schrieb am Fr., 3. Jan. 2020,
10:45:

This is simply how "with" works and one of the reasons why it is not considered good or safe by many.

Regards,
Sven

I seriously doubt this. You probably updated the RTL when updating the compiler.

Michael.

J. Gareth Moreton wrote

This was not a new property or a recent change to the Lazarus sources though.

It was a recent change in FPC RTL sources: r43841.

There was no clash before. The Options property was introduced yesterday in r43841.

FPC trunk is supported only in Lazarus trunk (and Lazarus stable branch if not forgotten :) ).

Ondrej

Oh right, okay.  That explains things then.  I would have thought though that it would have been test-compiled before being pushed to the main repository.  Sorry for the confusion - I assumed that Lazarus was guaranteed to build from the trunk.

Gareth aka. Kit

Sorry, and I'm also misunderstanding that the class belongs to the RTL, not Lazarus.  Not a good start to the day!

Gareth aka. Kit

AM J. Gareth Moreton wrote

Oh right, okay. That explains things then. I would have thought though that it would have been test-compiled before being pushed to the main repository.

No, the fpc devels are not responsible for Lazarus. The adding of TStrings.Options was mandatory (Delphi has it, so we must as well).

Sorry for the confusion - I assumed that Lazarus was guaranteed to build from the trunk.

This happens rather frequently, and cannot be really avoided, and if it happens we fix it in Lazarus trunk (and sometimes in Lazarus fixes as well).
It's not a big deal.