bjoernager/rust
bjoernager/rust
1
Fork 0
Code Activity

implement unwinding abi's (RFC 2945)

Browse source 
### Changes

    This commit implements unwind ABI's, specified in RFC 2945.

    We adjust the `rustc_middle::ty::layout::fn_can_unwind` function,
    used to compute whether or not a `FnAbi` object represents a
    function that should be able to unwind when `panic=unwind` is in
    use.

    Changes are also made to
    `rustc_mir_build::build::should_abort_on_panic` so that the
    function ABI is used to determind whether it should abort, assuming
    that the `panic=unwind` strategy is being used, and no explicit
    unwind attribute was provided.

 ### Tests

    Unit tests, checking that the behavior is correct for `C-unwind`,
    `stdcall-unwind`, `system-unwind`, and `thiscall-unwind`, are
    included. These alternative `unwind` ABI strings are specified in
    RFC 2945, in the "_Other `unwind` ABI strings_" section.

    Additionally, a test case is included to assert that the LLVM IR
    generated for an external function defined with the `C-unwind` ABI
    will be appropriately labeled with the `nounwind` LLVM attribute
    when the `panic=abort` compilation flag is used.

 ### Ignore Directives

    This commit uses `ignore-*` directives in two of our `*-unwind` ABI
    test cases.

    Specifically, the `stdcall-unwind` and `thiscall-unwind` test cases
    ignore architectures that do not support `stdcall` and `thiscall`,
    respectively.

    These directives are cribbed from
    `src/test/ui/c-variadic/variadic-ffi-1.rs` for `stdcall`, and
    `src/test/ui/extern/extern-thiscall.rs` for `thiscall`.
This commit is contained in:
katelyn a. martin 2020-09-10 13:38:39 -04:00
parent df45c579de
commit 0f33e9f281
7 changed files with 176 additions and 16 deletions
Download patch file Download diff file Expand all files Collapse all files

29
compiler/rustc_middle/src/ty/layout.rs
View file

@ -2562,6 +2562,7 @@ fn fn_can_unwind(
panic_strategy: PanicStrategy,
codegen_fn_attr_flags: CodegenFnAttrFlags,
call_conv: Conv,
abi: SpecAbi,
) -> bool {
if panic_strategy != PanicStrategy::Unwind {
// In panic=abort mode we assume nothing can unwind anywhere, so
@ -2586,17 +2587,16 @@ fn fn_can_unwind(
//
// 2. A Rust item using a non-Rust ABI (like `extern "C" fn foo() { ... }`).
//
// Foreign items (case 1) are assumed to not unwind; it is
// UB otherwise. (At least for now; see also
// rust-lang/rust#63909 and Rust RFC 2753.)
//
// Items defined in Rust with non-Rust ABIs (case 2) are also
// not supposed to unwind. Whether this should be enforced
// (versus stating it is UB) and *how* it would be enforced
// is currently under discussion; see rust-lang/rust#58794.
//
// In either case, we mark item as explicitly nounwind.
false
// In both of these cases, we should refer to the ABI to determine whether or not we
// should unwind. See Rust RFC 2945 for more information on this behavior, here:
// https://github.com/rust-lang/rfcs/blob/master/text/2945-c-unwind-abi.md
use SpecAbi::*;
match abi {
C { unwind } | Stdcall { unwind } | System { unwind } | Thiscall { unwind } => {
unwind
}
_ => false,
}
}
}
}
@ -2823,7 +2823,12 @@ where
c_variadic: sig.c_variadic,
fixed_count: inputs.len(),
conv,
can_unwind: fn_can_unwind(cx.tcx().sess.panic_strategy(), codegen_fn_attr_flags, conv),
can_unwind: fn_can_unwind(
cx.tcx().sess.panic_strategy(),
codegen_fn_attr_flags,
conv,
sig.abi,
),
};
fn_abi.adjust_for_abi(cx, sig.abi);
debug!("FnAbi::new_internal = {:?}", fn_abi);