check_expr_struct_fields: taint context with errors if struct definition is malformed #125947

olafes · 2024-06-04T00:39:26Z

Make sure we don't create instances of structs with ambiguous layout in const/static context, as this can lead to ICE's. Fragment below is a reduced version of both #125842 and #124464. With this change, the body of static initializer is tainted and we don't evaluate it at compile-time.

struct Struct { 
    field: Option<u8>,
    field: u8,
}

static STATIC: Struct = Struct { 
    field: 1,
};

pub fn main() {}

fixes #125842, fixes #124464, fixes #124552

rustbot · 2024-06-04T00:39:33Z

Thanks for the pull request, and welcome! The Rust team is excited to review your changes, and you should hear from @davidtwco (or someone else) some time within the next two weeks.

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compiler-errors · 2024-06-04T00:49:50Z

compiler/rustc_hir_typeck/src/expr.rs

+        let mut error_happened = if variant.fields.len() > remaining_fields.len() {
+            // Some field is defined more than once. Make sure we don't try to
+            // instantiate this struct in static/const context.
+            let guar = self.dcx().span_delayed_bug(expr.span, "struct fields have non-unique names");


No need to delay a bug here. Please taint the infcx below when we emit FieldMultiplySpecifiedInInitializer or report_unknown_field.

Here? I'm not sure this else branch is executed.

rust/compiler/rustc_hir_typeck/src/expr.rs

Lines 1703 to 1723 in e2c12b4

} else {

error_happened = true;

let guar = if let Some(prev_span) = seen_fields.get(&ident) {

tcx.dcx().emit_err(FieldMultiplySpecifiedInInitializer {

span: field.ident.span,

prev_span: *prev_span,

ident,

})

} else {

self.report_unknown_field(

adt_ty,

variant,

expr,

field,

hir_fields,

adt.variant_descr(),

)

};

Ty::new_error(tcx, guar)

};

Should I move my checking and tainting code to this line after the for loop?

rust/compiler/rustc_hir_typeck/src/expr.rs

Lines 1742 to 1744 in e2c12b4

}

// Make sure the programmer specified correct number of fields.

Actually, I guess I misread the issue. You probably want to do this instead on line 1874 where we call report_missing_fields?

I think none of the checks in check_expr_struct_fields really catch what this ICE is about. remaining_fields is a map that has field names as keys and duplicated fields just get overwritten. If we try to compile code given as an example in this PR, at 1873 remaining_fields will be empty and this branch will not be taken as well.

rust/compiler/rustc_hir_typeck/src/expr.rs

Lines 1873 to 1874 in e2c12b4

} else if adt_kind != AdtKind::Union && !remaining_fields.is_empty() {

debug!(?remaining_fields);

I could make remaining_fields distinguish between fields with the same name. I didn't feel confident in changing that much just to cover this, because error about struct definition is always there anyway.

compiler/rustc_hir_typeck/src/expr.rs

olafes · 2024-06-04T03:20:36Z

possibly related #123917

compiler-errors

Ok, sorry, yeah, I understand what the issue here is. I do wonder if there is a better place to do this tainting -- like rustc_mir_build -- rather than tangling it up with typeck 🤔.

Please squash this into one commit and then I can approve.

compiler-errors · 2024-06-04T19:52:07Z

compiler/rustc_hir_typeck/src/expr.rs

+        let mut error_happened = if variant.fields.len() > remaining_fields.len() {
+            // Some field is defined more than once. Make sure we don't try to
+            // instantiate this struct in static/const context.
+            let guar =
+                self.dcx().span_delayed_bug(expr.span, "struct fields have non-unique names");
+            self.set_tainted_by_errors(guar);
+
+            true
+        } else {
+            false
+        };


Can you split this up like so:

Suggested change

let mut error_happened = if variant.fields.len() > remaining_fields.len() {

// Some field is defined more than once. Make sure we don't try to

// instantiate this struct in static/const context.

let guar =

self.dcx().span_delayed_bug(expr.span, "struct fields have non-unique names");

self.set_tainted_by_errors(guar);

true

} else {

false

};

let mut error_happened = false;

if variant.fields.len() != remaining_fields.len() {

// Some field is defined more than once. Make sure we don't try to

// instantiate this struct in static/const context.

let guar =

self.dcx().span_delayed_bug(expr.span, "struct fields have non-unique names");

self.set_tainted_by_errors(guar);

error_happened = true;

}

rustbot · 2024-06-05T17:19:49Z

There are merge commits (commits with multiple parents) in your changes. We have a no merge policy so these commits will need to be removed for this pull request to be merged.

You can start a rebase with the following commands:

$ # rebase
$ git pull --rebase https://github.com/rust-lang/rust.git master
$ git push --force-with-lease

The following commits are merge commits:

a8faccf

…ion is malformed

rustbot · 2024-06-05T18:59:54Z

Some changes occurred in run-make tests.

cc @jieyouxu

The run-make-support library was changed

cc @jieyouxu

check_expr_struct_fields: taint context with errors if struct definit… Taint errors while checking `struct { field: 1 }` below if struct definition has duplicated fields so that we don't pass it to const eval. fixes rust-lang#125842, fixes rust-lang#124464, fixes rust-lang#124552 ```rust struct Struct { field: Option<u8>, field: u8, } static STATIC: Struct = Struct { field: 1, }; pub fn main() {} ``` (This was rust-lang#125947 but i messed something up, sorry) r? `@compiler-errors`

check_expr_struct_fields: taint context with errors if struct definit… Taint errors while checking `struct { field: 1 }` below if struct definition has duplicated fields so that we don't pass it to const eval. fixes rust-lang#125842, fixes rust-lang#124464, fixes rust-lang#124552 ```rust struct Struct { field: Option<u8>, field: u8, } static STATIC: Struct = Struct { field: 1, }; pub fn main() {} ``` (This was rust-lang#125947 but i messed something up, sorry) r? ``@compiler-errors``

Rollup merge of rust-lang#126045 - olafes:master, r=compiler-errors check_expr_struct_fields: taint context with errors if struct definit… Taint errors while checking `struct { field: 1 }` below if struct definition has duplicated fields so that we don't pass it to const eval. fixes rust-lang#125842, fixes rust-lang#124464, fixes rust-lang#124552 ```rust struct Struct { field: Option<u8>, field: u8, } static STATIC: Struct = Struct { field: 1, }; pub fn main() {} ``` (This was rust-lang#125947 but i messed something up, sorry) r? ``@compiler-errors``

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Oneirical and others added 5 commits June 5, 2024 20:55

rewrite emit test

46f8e86

rewrite bare-outfile test

98e1cbd

rewrite mixing-formats test

9fadfbd

Remove some allowed-makefiles

bc511a5

check_expr_struct_fields: taint context with errors if struct definit…

a73e140

…ion is malformed

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rustbot removed has-merge-commits PR has merge commits, merge with caution. S-waiting-on-author Status: This is awaiting some action (such as code changes or more information) from the author. labels Jun 5, 2024

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check_expr_struct_fields: taint context with errors if struct definit… #126045

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check_expr_struct_fields: taint context with errors if struct definition is malformed #125947

check_expr_struct_fields: taint context with errors if struct definition is malformed #125947

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rustbot commented Jun 5, 2024

	} else {
	error_happened = true;
	let guar = if let Some(prev_span) = seen_fields.get(&ident) {
	tcx.dcx().emit_err(FieldMultiplySpecifiedInInitializer {
	span: field.ident.span,
	prev_span: *prev_span,
	ident,
	})
	} else {
	self.report_unknown_field(
	adt_ty,
	variant,
	expr,
	field,
	hir_fields,
	adt.variant_descr(),
	)
	};

	Ty::new_error(tcx, guar)
	};

	}

	// Make sure the programmer specified correct number of fields.

	} else if adt_kind != AdtKind::Union && !remaining_fields.is_empty() {
	debug!(?remaining_fields);

check_expr_struct_fields: taint context with errors if struct definition is malformed #125947

check_expr_struct_fields: taint context with errors if struct definition is malformed #125947

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