On Thu, 22 Feb 2024, Martin Frb via fpc-devel wrote:
https://www.freepascal.org/docs-html/rtl/system/default.html
Default is a compiler intrinsic: it returns for every type T a default
value. In essence, this is a block of memory that is zeroed out. It can be
used to correctly initialize any type, and more importantly, a managed
type. It also works using a generic type template.
But zero isn't always a valid value => so how can it be used to initialize a
type where that is invalid.
The below will runtime error "invalid enum value".
(And also, in the past, I saw it pointed out countless times, that setting an
enum to an ordinal value that is not matching any of its members does not
have a defined behaviour).
So is that a bug in Default?
Or is the documentation wrong "any type"? (it contradicts itself anyway
"zeroed" <> "any type")
I have amended the documentation to say that a block of zeroes is not
necessarily a correct value, and have given 3 examples of types where it can
go wrong.
Michael.
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