Correct iterator adaptor Chain
The iterator protocol specifies that the iteration ends with the return
value `None` from `.next()` (or `.next_back()`) and it is unspecified
what further calls return. The chain adaptor must account for this in
its DoubleEndedIterator implementation.
It uses three states:
- Both `a` and `b` are valid
- Only the Front iterator (`a`) is valid
- Only the Back iterator (`b`) is valid
The fourth state (neither iterator is valid) only occurs after Chain has
returned None once, so we don't need to store this state.
Fixes#26316
The iterator protocol specifies that the iteration ends with the return
value `None` from `.next()` (or `.next_back()`) and it is unspecified
what further calls return. The chain adaptor must account for this in
its DoubleEndedIterator implementation.
It uses three states:
- Both `a` and `b` are valid
- Only the Front iterator (`a`) is valid
- Only the Back iterator (`b`) is valid
The fourth state (neither iterator is valid) only occurs after Chain has
returned None once, so we don't need to store this state.
Fixes#26316
According to https://msdn.microsoft.com/en-us/library/windows/desktop/ms679351(v=vs.85).aspx:
> If the function succeeds, the return value is the number of TCHARs stored in the output buffer,
> excluding the terminating null character.
_**Completely untested**_… since I have no Windows machine or anything of a sort to test this on.
r? @aturon
Reserving lower_bound bytes was just silly. It’d be perfectly reasonable
to have empty strings in the iterator, which could cause superfluous
reallocation of the string, or to have more than one byte per string,
which could cause additional reallocation (in practice it’ll balance
out). The added complexity of this logic is simply pointless, adding
a little bloat with no demonstrable advantage and slight disadvantage.
On Linux the flag is just ignored if it is not supported:
https://lwn.net/Articles/588444/
Still needs the values of O_CLOEXEC on the BSDs.
Touches #24237.
- All the libstd tests are passing in the optimized build against
a Zenfone2 and the x86 Android emulator.
I haven't tested the other libraries though.
Some hoedown FFI changes:
- `HOEDOWN_EXT_NO_INTRA_EMPHASIS` constant changed.
- Updated/tidied up all callback function signatures.
- All opaque data access has an additional layer of indirection for some reason (`hoedown_renderer_data`).
This also fixes#27862.
This increases regionck performance greatly - type-checking on
librustc decreased from 9.1s to 8.1s. Because of Amdahl's law,
total performance is improved only by about 1.5% (LLVM wizards,
this is your opportunity to shine!).
before:
576.91user 4.26system 7:42.36elapsed 125%CPU (0avgtext+0avgdata 1142192maxresident)k
after:
566.50user 4.84system 7:36.84elapsed 125%CPU (0avgtext+0avgdata 1124304maxresident)k
I am somewhat worried really need to find out why we have this Red Queen's
Race going on here. Originally I suspected it may be a problem from RFC1214's
warnings, but it seems to be an effect from other changes.
However, the increase seems to be mostly in LLVM's time, so I guess
it's the LLVM wizards' problem.
r? @nikomatsakis
Reserving lower_bound bytes was just silly. It’d be perfectly reasonable
to have empty strings in the iterator, which could cause superfluous
reallocation of the string, or to have more than one byte per string,
which could cause additional reallocation (in practice it’ll balance
out). The added complexity of this logic is simply pointless, adding
a little bloat with no demonstrable advantage and slight disadvantage.
The functions is useful for all kinds of fat pointers, but get_len()
just feels so wrong for trait object fat pointers. Let's use get_meta()
because that's rather neutral.
This increases regionck performance greatly - type-checking on
librustc decreased from 9.1s to 8.1s. Because of Amdahl's law,
total performance is improved only by about 1.5% (LLVM wizards,
this is your opportunity to shine!).
before:
576.91user 4.26system 7:42.36elapsed 125%CPU (0avgtext+0avgdata 1142192maxresident)k
after:
566.50user 4.84system 7:36.84elapsed 125%CPU (0avgtext+0avgdata 1124304maxresident)k
I am somewhat worried really need to find out why we have this Red Queen's
Race going on here. Originally I suspected it may be a problem from RFC1214's
warnings, but it seems to be an effect from other changes.
However, the increase seems to be mostly in LLVM's time, so I guess
it's the LLVM wizards' problem.
Since enums are namespaced now, should we also remove the `Fk` prefixes from `FnKind` and remove the reexport? (The reexport must be removed because otherwise it clashes with glob imports containing `ItemFn`). IMO writing `FnKind::Method` is much clearer than `FkMethod`.
It doesn't really make sense for DefId to be in libsyntax -- it is concerned with a single crate only. It is the compiler that understands the idea of many crates. (At some point, there might be a useful intermediate point here.) This is a refactoring in support of incr. compilation, which will be adjusting the notion of a DefId to make it more durable across compilations.
This will probably be a [breaking-change] for every plugin ever. You need to adjust things as follows:
use rustc::middle::def_id::{DefId, LOCAL_CRATE}; // two most common definitions
ast_util::is_local(def_id) => def_id.is_local()
ast_util::local_def(node_id) => DefId::local(node_id)
