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Make deref_nullptr deny by default instead of warn #148122

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Make deref_nullptr deny by default instead of warn #148122

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Make deref_nullptr deny by default instead of warn
saethlin Oct 26, 2025
3b9de6f
Expect compilation failure
saethlin Oct 26, 2025
ab634f5
Don't lint on derefs of null pointers to ZSTs
saethlin Nov 6, 2025
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2 changes: 1 addition & 1 deletion compiler/rustc_lint/src/builtin.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -2716,7 +2716,7 @@ declare_lint! {
///
/// [undefined behavior]: https://doc.rust-lang.org/reference/behavior-considered-undefined.html
pub DEREF_NULLPTR,
Warn,
Deny,
"detects when an null pointer is dereferenced"
}

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2 changes: 1 addition & 1 deletion tests/ui/lint/lint-forbid-internal-unsafe.rs
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Expand Up @@ -13,5 +13,5 @@ macro_rules! evil {

fn main() {
println!("{}", evil!(*(0 as *const u8)));
//~^ WARNING dereferencing a null pointer
//~^ ERROR dereferencing a null pointer
}
6 changes: 3 additions & 3 deletions tests/ui/lint/lint-forbid-internal-unsafe.stderr
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Expand Up @@ -10,13 +10,13 @@ note: the lint level is defined here
LL | #![forbid(unsafe_code)]
| ^^^^^^^^^^^

warning: dereferencing a null pointer
error: dereferencing a null pointer
--> $DIR/lint-forbid-internal-unsafe.rs:15:26
|
LL | println!("{}", evil!(*(0 as *const u8)));
| ^^^^^^^^^^^^^^^^^ this code causes undefined behavior when executed
|
= note: `#[warn(deref_nullptr)]` on by default
= note: `#[deny(deref_nullptr)]` on by default

error: aborting due to 1 previous error; 1 warning emitted
error: aborting due to 2 previous errors

2 changes: 1 addition & 1 deletion tests/ui/unreachable-code/unreachable-bool-read-7246.rs
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Expand Up @@ -5,7 +5,7 @@ use std::ptr;
pub unsafe fn g() {
return;
if *ptr::null() {}; //~ ERROR unreachable
//~| WARNING dereferencing a null pointer
//~| ERROR dereferencing a null pointer
}

pub fn main() {}
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6 changes: 3 additions & 3 deletions tests/ui/unreachable-code/unreachable-bool-read-7246.stderr
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Expand Up @@ -12,13 +12,13 @@ note: the lint level is defined here
LL | #![deny(unreachable_code)]
| ^^^^^^^^^^^^^^^^

warning: dereferencing a null pointer
error: dereferencing a null pointer
--> $DIR/unreachable-bool-read-7246.rs:7:8
|
LL | if *ptr::null() {};
| ^^^^^^^^^^^^ this code causes undefined behavior when executed
|
= note: `#[warn(deref_nullptr)]` on by default
= note: `#[deny(deref_nullptr)]` on by default

error: aborting due to 1 previous error; 1 warning emitted
error: aborting due to 2 previous errors

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