On Mon, Jul 27, 2020 at 09:53:31AM -0600, Martin Sebor via Gcc-patches wrote:
> Return a pointer P to a NUL-terminated string containing
> the sequence of bytes corresponding to the representation
> of the object referred to by SRC (or a subsequence of such
> bytes within it if SRC is a reference to an initialized
> constant array plus some constant offset).
>
> I.e., c_getstr returns a STRING_CST for arbitrary non-string
> constants. This enables optimizations like the by-pieces
> expansion of calls to raw memory functions like memcpy, or
> the folding of other raw memory calls like memchr with non-
> string arguments.
>
> c_getstr relies on string_constant for that. Restricting
> the latter function to just character types prevents these
> optimizations for zero-initialized constants of other types.
> A test case that shows the difference to the by-pieces
> expansion goes something like this:
Having STRING_CST in the compiler with arbitrary array type is IMHO a very
bad idea, so if you want something like that, you should come up with a
different representation for that, not STRING_CSTs.
Because most of the compiler assumes STRING_CSTs are what it says, string
literals where elements are some kind of characters, don't have to be
narrow, but better should be integral.
Maybe returning a CONSTRUCTOR with no elements with the right type is a
better idea for that, that in the compiler stands for zero initialized
aggregate.
Jakub
