On Sun, 21 May 2023, Hairy Pixels via fpc-pascal wrote:
I've never really used exceptions myself in Pascal (with the exception of
breaking out of deeply recursive function calls) so I don't know all the rules.
In this example lets say you call Test() which allocates some memory and
then calls out to another function in another unit which raises (the
programmer doesn't know this because FPC doesn't mark the function as
throwing exceptions). Now the Test() function will exit early before
freeing the memory.
What are you supposed to do here? The only thing I can think of is to
wrap every function in try..finally which COULD raise an exception but
that's a huge mess because literally any function could raise.
====================================
procedure DoThis;
begin
raise Exception.Create('dead');
end;
procedure Test;
begin
TObject.Create;
// call some code in other unit which raise an exception
DoThis;
end;
Your example will leak memory in any case, even if there is no exception,
since you're not freeing the object anywhere..
Assuming the result of A is not used outside of Test, the following is the
only solution:
procedure Test;
var
A : TObject;
begin
A:=TObject.Create;
Try
// call some code in other unit which raise an exception
DoThis;
finally
A.Free
end;
end;
You can try to use interfaces, they will be managed by the compiler.
Alternatively, using generics and management operators you can
create a record that will automatically free the object at the
end of the procedure.
Michael.
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