Reattach all grandchildren when constructing specialization graph.
Specialization graphs are constructed by incrementally adding impls in the order of declaration. If the impl being added has its specializations in the graph already, they should be reattached under the impl. However, the current implementation only reattaches the one found first. Therefore, in the following specialization graph,
```
Tr1
|
I3
/ \
I1 I2
```
If `I1`, `I2`, and `I3` are declared in this order, the compiler mistakenly constructs the following graph:
```
Tr1
/ \
I3 I2
|
I1
```
This patch fixes the reattach procedure to include all specializing grandchildren-to-be.
Fixes#50452.
`concurrent_recv_timeout_and_upgrade` reproduces a problem 100%
times on my MacBook with command:
```
./x.py test --stage 0 ./src/test/run-pass/mpsc_stress.rs
```
Thus it is commented out.
Other tests cases were useful for catching another test cases
which may arise during the fix.
This diff is a part of my previous rewrite attempt: #42883
CC #39364
std: Synchronize access to global env during `exec`
This commit, after reverting #55359, applies a different fix for #46775
while also fixing #55775. The basic idea was to go back to pre-#55359
libstd, and then fix#46775 in a way that doesn't expose #55775.
The issue described in #46775 boils down to two problems:
* First, the global environment is reset during `exec` but, but if the
`exec` call fails then the global environment was a dangling pointer
into free'd memory as the block of memory was deallocated when
`Command` is dropped. This is fixed in this commit by installing a
`Drop` stack object which ensures that the `environ` pointer is
preserved on a failing `exec`.
* Second, the global environment was accessed in an unsynchronized
fashion during `exec`. This was fixed by ensuring that the
Rust-specific environment lock is acquired for these system-level
operations.
Thanks to Alex Gaynor for pioneering the solution here!
Closes#55775
This commit, after reverting #55359, applies a different fix for #46775
while also fixing #55775. The basic idea was to go back to pre-#55359
libstd, and then fix#46775 in a way that doesn't expose #55775.
The issue described in #46775 boils down to two problems:
* First, the global environment is reset during `exec` but, but if the
`exec` call fails then the global environment was a dangling pointer
into free'd memory as the block of memory was deallocated when
`Command` is dropped. This is fixed in this commit by installing a
`Drop` stack object which ensures that the `environ` pointer is
preserved on a failing `exec`.
* Second, the global environment was accessed in an unsynchronized
fashion during `exec`. This was fixed by ensuring that the
Rust-specific environment lock is acquired for these system-level
operations.
Thanks to Alex Gaynor for pioneering the solution here!
Closes#55775
Co-authored-by: Alex Gaynor <alex.gaynor@gmail.com>
xLTO: Don't pass --plugin-opt=thin to LLD. That's not supported anymore.
It seems that `-plugin-opt=thin` is not needed anymore when invoking LLD for ThinLTO. Unfortunately, still passing the option makes LLD crash instead of giving a deprecation warning or something.
This commit changes the test code to compare against easier-to-read, static values instead of relying on the result of `wrapping_add()` which may or may not result in the value that we expect.
Check for negative impls when finding auto traits
Fixes#55321
When AutoTraitFinder begins examining a type, it checks for an explicit
negative impl. However, it wasn't checking for negative impls found when
calling 'select' on predicates found from nested obligations.
This commit makes AutoTraitFinder check for negative impls whenever it
makes a call to 'select'. If a negative impl is found, it immediately
bails out.
Normal users of SelectioContext don't need to worry about this, since
they stop as soon as an Unimplemented error is encountered. However, we
add predicates to our ParamEnv when we encounter this error, so we need
to handle negative impls specially (so that we don't try adding them to
our ParamEnv).
