Make sNaN removal code tolerate different sNaN encodings
IEEE 754-1985 specifies the encoding of NaN floating point numbers,
but while it mentions that NaNs can be subdivided into signaling
and quiet ones, it doesn't fix the encoding of signaling NaNs in binary
formats. This led to different implementations (CPUs) having different
encodings. IEEE 754-2008 finally specified the encoding of signaling NaNs
but some architectures are compatible with it, while others aren't.
Certain MIPS and PA-RISC CPUs have different encodings for signaling
NaNs.
In order to have the float <-> binary cast feature of the std library be
portable to them, we don't mask any quiet NaNs like we did before (only
being compliant to IEEE 754-2008 and nothing else), but instead we
simply pass a known good NaN instead.
Note that in the code removed there was a bug; the 64 bit mask for quiet
NaNs should have been `0x0008000000000000` instead of the specified
`0x0001000000000000`.
Delete deprecated & unstable range-specific `step_by`
Using the new one is annoying while this one exists, since the inherent method hides the one on iterator.
Tracking issue: #27741
Replacement: #41439
Deprecation: #42310 for 1.19
Fixes#41477
When trying to use dedup_by to merge some auxiliary information from
removed elements into kept elements, I was surprised to observe that
vec.dedup_by(same_bucket) calls same_bucket(a, b) where b appears
before a in the vector, and discards a when true is returned. This
argument order is probably a bug, but since it has already been
stabilized, I guess we should document it as a feature and move on.
(Vec::dedup also uses == with this unexpected argument order, but I
figure that’s not important since == is expected to be symmetric with
no side effects.)
Signed-off-by: Anders Kaseorg <andersk@mit.edu>
IEEE 754-1985 specifies the encoding of NaN floating point numbers,
but while it mentions that NaNs can be subdivided into signaling
and quiet ones, it doesn't fix the encoding of signaling NaNs in binary
formats. This led to different implementations (CPUs) having different
encodings. IEEE 754-2008 finally specified the encoding of signaling NaNs
but some architectures are compatible with it, while others aren't.
Certain MIPS and PA-RISC CPUs have different encodings for signaling
NaNs.
In order to have the float <-> binary cast feature of the std library be
portable to them, we don't mask any quiet NaNs like we did before (only
being compliant to IEEE 754-2008 and nothing else), but instead we
simply pass a known good NaN instead.
Note that in the code removed there was a bug; the 64 bit mask for quiet
NaNs should have been `0x0008000000000000` instead of the specified
`0x0001000000000000`.
This adds docs for the Debug* structs as well as examples from the
Formatter::debug_* methods, so that a user knows how to construct them.
I added these examples as the builders module is not public and hence
the debug_*_new() functions are not available to a user.
r? @steveklabnik
Review comments.
Mainly adding in the links for all of the structs and functions.
Remove rust tag on code blocks.
Output column number info when panicking
Outputs the column number when panicking. Useful when you e.g. have code like `foo[i] = bar[k] + bar[l]` and you get a panic with index out of bounds, or when you have an expression like `a = b + c + d + e` and the addition overflows. Now you know which operation to blame!
The format is `file:line:column`, just like for compiler errors. Example output with the patch:
```
thread 'main' panicked at 'index out of bounds: the len is 5 but the index is 8', src/main.rs:3:8
```
As some of the API between the compiler and the library landscape gets broken, this is a bit hackier than I'd originally wanted it to be.
* `panic` and `panic_bounds_check` lang items got an additional column param, on stage0 I still have to use the previous version. After a SNAP this should be resolved.
* For `#[derive(RustcDeserialze)]`, stage0 requires a fixed signature for `std::rt::begin_panic`, so we can't change it right away. What we need to do instead is to keep the signature, and add a `begin_panic_new` function that we use in later stages instead. After a SNAP we can change the `begin_panic` function and rely on it instead of `begin_panic_new`, and one SNAP later we can remove `begin_panic_new`.
* Fortunately I didn't have to break anything about the panic hook API, I could easily extend it.
Note that debuginfo remains unchanged, so RUST_BACKTRACE output won't contain any column info. See issue #42921 for discussion on including the column in debuginfo.
report the total number of errors on compilation failure
Prior to this PR, when we aborted because a "critical pass" failed, we displayed the number of errors from that critical pass. While that's the number of errors that caused compilation to abort in *that place*, that's not what people really want to know. Instead, always report the total number of errors, and don't bother to track the number of errors from the last pass that failed.
This changes the compiler driver API to handle errors more smoothly, therefore is a compiler-api-[breaking-change].
Fixes#42793.
r? @eddyb
Prior to this PR, when we aborted because a "critical pass" failed, we
displayed the number of errors from that critical pass. While that's the
number of errors that caused compilation to abort in *that place*,
that's not what people really want to know. Instead, always report the
total number of errors, and don't bother to track the number of errors
from the last pass that failed.
This changes the compiler driver API to handle errors more smoothly,
and therefore is a compiler-api-[breaking-change].
Fixes#42793.
bootstrap: Fix all the pep-8 issues reported by flake8
This commit also adds a few missing docstrings.
Today, after reading this [article](https://blog.rust-lang.org/2017/06/27/Increasing-Rusts-Reach.html), I downloaded this project and started building from source. In the meantime, I began to read the `bootstrap.py`, to know more about the building process, and I made a few changes, this is my first contribution to the project, hope you like it.
BTW, I have a few doubts about the `bootstrap.py`, any guidance is more than welcome:
* Where can I find the unit tests for this script? In case it doesn't exist yet, do you like to include some unit tests with pytest?
* Some methods like `fix_executable`, `get_string`, and `exe_suffix` in the `RustBuild` class should be converted to a function because it doesn't use `self` anywhere. What do you think?
