bjoernager/rust
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Rollup merge of #103061 - Amanieu:rewrite_alloc_error_handler, r=bjorn3

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Rewrite implementation of `#[alloc_error_handler]`

The new implementation doesn't use weak lang items and instead changes `#[alloc_error_handler]` to an attribute macro just like `#[global_allocator]`.

The attribute will generate the `__rg_oom` function which is called by the compiler-generated `__rust_alloc_error_handler`. If no `__rg_oom` function is defined in any crate then the compiler shim will call `__rdl_oom` in the alloc crate which will simply panic.

This also fixes link errors with `-C link-dead-code` with `default_alloc_error_handler`: `__rg_oom` was previously defined in the alloc crate and would attempt to reference the `oom` lang item, even if it didn't exist. This worked as long as `__rg_oom` was excluded from linking since it was not called.

This is a prerequisite for the stabilization of `default_alloc_error_handler` (#102318).
This commit is contained in:
Dylan DPC 2022-11-01 14:12:25 +05:30 • committed by GitHub
commit 43634675f6
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40 changed files with 441 additions and 166 deletions
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5
compiler/rustc_hir/src/lang_items.rs
View file

@ -126,14 +126,12 @@ impl<CTX> HashStable<CTX> for LangItem {
}
/// Extracts the first `lang = "$name"` out of a list of attributes.
/// The attributes `#[panic_handler]` and `#[alloc_error_handler]`
/// are also extracted out when found.
/// The `#[panic_handler]` attribute is also extracted out when found.
pub fn extract(attrs: &[ast::Attribute]) -> Option<(Symbol, Span)> {
attrs.iter().find_map(|attr| {
Some(match attr {
_ if attr.has_name(sym::lang) => (attr.value_str()?, attr.span),
_ if attr.has_name(sym::panic_handler) => (sym::panic_impl, attr.span),
_ if attr.has_name(sym::alloc_error_handler) => (sym::oom, attr.span),
_ => return None,
})
})
@ -240,7 +238,6 @@ language_item_table! {
ExchangeMalloc, sym::exchange_malloc, exchange_malloc_fn, Target::Fn, GenericRequirement::None;
BoxFree, sym::box_free, box_free_fn, Target::Fn, GenericRequirement::Minimum(1);
DropInPlace, sym::drop_in_place, drop_in_place_fn, Target::Fn, GenericRequirement::Minimum(1);
Oom, sym::oom, oom, Target::Fn, GenericRequirement::None;
AllocLayout, sym::alloc_layout, alloc_layout, Target::Struct, GenericRequirement::None;
Start, sym::start, start_fn, Target::Fn, GenericRequirement::Exact(1);

1
compiler/rustc_hir/src/weak_lang_items.rs
View file

@ -27,5 +27,4 @@ weak_lang_items! {
PanicImpl, rust_begin_unwind;
EhPersonality, rust_eh_personality;
EhCatchTypeinfo, rust_eh_catch_typeinfo;
Oom, rust_oom;
}