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2012, Tuesday April 10

How function results are allocated

By A.Bouchez on 2012, Tuesday April 10, 11:53 - Pascal Programing

One potential issue with Delphi coding, is about how the result of a functions are implemented.

If you forget to set a result value to a function, you'll get a compiler warning.
Never underestimate such warning: IMHO this is not a warning, but an error.

And you should better be aware of the handling of reference-counted types (e.g. string) in a function results: those are passed the stack as var parameters, so the result of a function may be set even if an exception is raised during function execution!

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2012, Thursday February 9

Using SetLength or SetString

By A.Bouchez on 2012, Thursday February 9, 10:54 - Pascal Programing

Some Delphi users even do not know the existence of the SetString function.

As stated by the official documentation:

procedure SetString(var S: String; Buffer: PChar; Length: Integer);

For a long string variable, SetString sets S to reference a newly allocated string of the given length. If the Buffer parameter is not nil, SetString then copies Len characters from Buffer into the string; otherwise, the content of the new string is left uninitialized. If there is not enough memory available to create the string, an EOutOfMemory exception is raised. Following a call to SetString, S is guaranteed to reference a unique string (a string with a reference count of one).

Some have noticed that in our libraries, I sometimes use SetString instead of SetLength.
When the string is already allocated, it could be faster to use SetString, if you are sure that you will overwrite the string content.

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