[Pitch] Safe loading of integer values from `RawSpan`

[glessard (Guillaume Lessard)]

I have started a second pitch thread, after having significantly reworked the proposal.

[Pitch 2] Safe loading of values from `RawSpan`

This is a second pitch thread for this feature, after it was significantly reworked. The first pitch thread was [Pitch] Safe loading of integer values from `RawSpan` . The most significant change is the introduction of a new layout constraint, FullyInhabited. The safe API are now constrained by this protocol, or by this protocol in combination with FixedWidthInteger. Safe loading API for RawSpan Introduction We propose the introduction of a set of safe API to load values of certain safe types …

[grynspan (Jonathan Grynspan)]

In terms of what the OS will accept, true. In terms of a non-trapping (in C parlance) bit pattern, any will do.

(I think we're perhaps talking past each other.)

[scanon (Steve Canon)]

(I think we're perhaps talking past each other.)

Indeed; “fully inhabited” in the sense Guillaume has been using it here does not mean “does not have a trap representation” (in C standardese), but rather “loading an arbitrary sequence of bytes interpreted as T and then using it cannot violate program invariants and result in UB.”

[grynspan (Jonathan Grynspan)]

Understood! Sorry for derailing the conversation—I think we need to be clear in our terminology here (see my previous reply to @John_McCall) but I get that we're not talking about "inhabited" the same way we do when e.g. filling out enum bits.

I'll go back to the… cave… that I inhabit.