Previous Stacked Borrows diagnostics were missing a lot of information
about the state of the interpreter, and it was difficult to add
additional state because it was threaded through all the intervening
function signatures.
This change factors a lot of the arguments which used to be passed
individually to many stacked borrows functions into a single
`DiagnosticCx`, which is built in `Stacks::for_each`, and since it
wraps a handle to `AllocHistory`, we can now handle more nuanced
things like heterogeneous borrow of `!Freeze` types.
Breaking posix_memalign precondition is not UB
The `size==0` test here might be overtesting, but I figured might as well test it and leave a comment saying it is fine to remove it if the implementation changes.
Fixes#2099
fix RUSTC_BACKTRACE always being set
I kept wondering why Miri programs, whenever isolation is disabled, behave as if RUSTC_BACKTRACE was set. Finally I realized it's because some early rustc setup code sets that env var, and that is then propagated to the interpreted program.
So fix that by taking a copy of the environment before any rustc setup, and use that copy as the basis for what is provided to the interpreted program.
implement some missing float functions
With this we support the entire float API surface of the standard library. :)
Also fixes https://github.com/rust-lang/miri/issues/2468 by using host floats to implement FMA.
fix build.rs invoking RUSTC to do check builds
This makes the Miri driver, when invokved via the RUSTC env var from inside a build script, behave almost entirely like rustc. I had to redo how we propagate sysroot information for this (which is actually back to how we used to do sysroot propagation many years ago).
Fixes https://github.com/rust-lang/miri/issues/2431
this requires a change in sysroot handling: miri driver now requires
MIRI_SYSROOT to be set when it is in 'target' mode, rather than relying on
`--sysroot` always being present.
