The explicit include is needed for clangd to not get confused somehow,
which is also what threw me off initially and made me pick the wrong
constructor.
The (pointer, number, number) constructor first constructs a C string
and then takes a substring from that, but we didn't specify that the
buffer needs to be NUL-terminated, and then what would be the point of
the size argument anyway...
basic_string.h:
> basic_string(const _Tp& __t, size_type __pos, size_type __n,
> const _Alloc& __a = _Alloc())
> : basic_string(_S_to_string_view(__t).substr(__pos, __n), __a) { }
Valgrind on nixops4/rust/nix-flake tests:
==1344422== Conditional jump or move depends on uninitialised value(s)
==1344422== at 0x48513E8: strlen (vg_replace_strmem.c:505)
==1344422== by 0x488E941: UnknownInlinedFun (char_traits.h:391)
==1344422== by 0x488E941: UnknownInlinedFun (string_view:141)
==1344422== by 0x488E941: UnknownInlinedFun (basic_string.h:790)
==1344422== by 0x488E941: nix_flake_reference_and_fragment_from_string (nix_api_flake.cc:81)
==1344422== by 0x127332: nix_flake::FlakeReference::parse_with_fragment (lib.rs:123)
The short answer for why we need to do this is so we can consistently do
`#include "nix/..."`. Without this change, there are ways to still make
that work, but they are hacky, and they have downsides such as making it
harder to make sure headers from the wrong Nix library (e..g.
`libnixexpr` headers in `libnixutil`) aren't being used.
The C API alraedy used `nix_api_*`, so its headers are *not* put in
subdirectories accordingly.
Progress on #7876
We resisted doing this for a while because it would be annoying to not
have the header source file pairs close by / easy to change file
path/name from one to the other. But I am ameliorating that with
symlinks in the next commit.
