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Improve miri comments

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This commit is contained in:
bjorn3 2023-02-12 17:14:28 +00:00
parent efb9c30ed2
commit 568deb7ece
1 changed files with 14 additions and 1 deletions
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15
src/tools/miri/src/shims/foreign_items.rs
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@ -358,7 +358,11 @@ pub trait EvalContextExt<'mir, 'tcx: 'mir>: crate::MiriInterpCxExt<'mir, 'tcx> {
match allocator_kind {
AllocatorKind::Global => {
// `__rust_*` is defined by `#[global_allocator]` if `#[global_allocator]` is used
// When `#[global_allocator]` is used, `__rust_*` is defined by the macro expansion
// of this attribute rather than generated by the allocator shim. As such we have
// to call the definition produced by `#[global_allocator]` instead of the shim like
// in the case of `#[global_allocator]` not existing. Somewhat unintuitively doing
// so is done by returning `NotSupported`.
return Ok(EmulateByNameResult::NotSupported);
}
AllocatorKind::Default => {
@ -555,6 +559,9 @@ pub trait EvalContextExt<'mir, 'tcx: 'mir>: crate::MiriInterpCxExt<'mir, 'tcx> {
// Rust allocation
"__rust_alloc" | "miri_alloc" => {
let default = |this: &mut MiriInterpCx<'mir, 'tcx>| {
// Only call `check_shim` when `#[global_allocator]` isn't used. The macro
// expansion of `#[global_allocator]` defines this symbol and `check_shim`
// checks that there exists no definition of a shim.
let [size, align] = this.check_shim(abi, Abi::Rust, link_name, args)?;
let size = this.read_target_usize(size)?;
let align = this.read_target_usize(align)?;
@ -587,6 +594,8 @@ pub trait EvalContextExt<'mir, 'tcx: 'mir>: crate::MiriInterpCxExt<'mir, 'tcx> {
}
"__rust_alloc_zeroed" => {
return this.emulate_allocator(|this| {
// See the comment for `__rust_alloc` why `check_shim` is only called in the
// default case.
let [size, align] = this.check_shim(abi, Abi::Rust, link_name, args)?;
let size = this.read_target_usize(size)?;
let align = this.read_target_usize(align)?;
@ -610,6 +619,8 @@ pub trait EvalContextExt<'mir, 'tcx: 'mir>: crate::MiriInterpCxExt<'mir, 'tcx> {
}
"__rust_dealloc" | "miri_dealloc" => {
let default = |this: &mut MiriInterpCx<'mir, 'tcx>| {
// See the comment for `__rust_alloc` why `check_shim` is only called in the
// default case.
let [ptr, old_size, align] =
this.check_shim(abi, Abi::Rust, link_name, args)?;
let ptr = this.read_pointer(ptr)?;
@ -643,6 +654,8 @@ pub trait EvalContextExt<'mir, 'tcx: 'mir>: crate::MiriInterpCxExt<'mir, 'tcx> {
}
"__rust_realloc" => {
return this.emulate_allocator(|this| {
// See the comment for `__rust_alloc` why `check_shim` is only called in the
// default case.
let [ptr, old_size, align, new_size] =
this.check_shim(abi, Abi::Rust, link_name, args)?;
let ptr = this.read_pointer(ptr)?;