fix: don't lint null as UB for volatile

Also remove a now-unneeded `allow` line.

Author: LuigiPiucco

compiler/rustc_lint/src/ptr_nulls.rs

@@ -160,12 +160,10 @@ impl<'tcx> LateLintPass<'tcx> for PtrNullChecks {
                 let (arg_indices, are_zsts_allowed): (&[_], _) = match diag_name {
                     sym::ptr_read
                     | sym::ptr_read_unaligned
-                    | sym::ptr_read_volatile
                     | sym::ptr_replace
                     | sym::ptr_write
                     | sym::ptr_write_bytes
-                    | sym::ptr_write_unaligned
-                    | sym::ptr_write_volatile => (&[0], true),
+                    | sym::ptr_write_unaligned => (&[0], true),
                     sym::slice_from_raw_parts | sym::slice_from_raw_parts_mut => (&[0], false),
                     sym::ptr_copy
                     | sym::ptr_copy_nonoverlapping

tests/ui/lint/invalid_null_args.rs

@@ -58,10 +58,9 @@ unsafe fn null_ptr() {
     let _a: A = ptr::read_unaligned(ptr::null_mut());
     //~^ ERROR calling this function with a null pointer is undefined behavior
 
+    // These two should *not* fire the lint.
     let _a: A = ptr::read_volatile(ptr::null());
-    //~^ ERROR calling this function with a null pointer is undefined behavior
     let _a: A = ptr::read_volatile(ptr::null_mut());
-    //~^ ERROR calling this function with a null pointer is undefined behavior
 
     let _a: A = ptr::replace(ptr::null_mut(), v);
     //~^ ERROR calling this function with a null pointer is undefined behavior
@@ -82,8 +81,8 @@ unsafe fn null_ptr() {
     ptr::write_unaligned(ptr::null_mut(), v);
     //~^ ERROR calling this function with a null pointer is undefined behavior
 
+    // This one should *not* fire the lint.
     ptr::write_volatile(ptr::null_mut(), v);
-    //~^ ERROR calling this function with a null pointer is undefined behavior
 
     ptr::write_bytes::<usize>(ptr::null_mut(), 42, 0);
     //~^ ERROR calling this function with a null pointer is undefined behavior

tests/ui/lint/invalid_null_args.stderr

@@ -164,27 +164,7 @@ LL |     let _a: A = ptr::read_unaligned(ptr::null_mut());
    = help: for more information, visit <https://doc.rust-lang.org/std/ptr/index.html> and <https://doc.rust-lang.org/reference/behavior-considered-undefined.html>
 
 error: calling this function with a null pointer is undefined behavior, even if the result of the function is unused
-  --> $DIR/invalid_null_args.rs:61:17
-   |
-LL |     let _a: A = ptr::read_volatile(ptr::null());
-   |                 ^^^^^^^^^^^^^^^^^^^-----------^
-   |                                    |
-   |                                    null pointer originates from here
-   |
-   = help: for more information, visit <https://doc.rust-lang.org/std/ptr/index.html> and <https://doc.rust-lang.org/reference/behavior-considered-undefined.html>
-
-error: calling this function with a null pointer is undefined behavior, even if the result of the function is unused
-  --> $DIR/invalid_null_args.rs:63:17
-   |
-LL |     let _a: A = ptr::read_volatile(ptr::null_mut());
-   |                 ^^^^^^^^^^^^^^^^^^^---------------^
-   |                                    |
-   |                                    null pointer originates from here
-   |
-   = help: for more information, visit <https://doc.rust-lang.org/std/ptr/index.html> and <https://doc.rust-lang.org/reference/behavior-considered-undefined.html>
-
-error: calling this function with a null pointer is undefined behavior, even if the result of the function is unused
-  --> $DIR/invalid_null_args.rs:66:17
+  --> $DIR/invalid_null_args.rs:65:17
    |
 LL |     let _a: A = ptr::replace(ptr::null_mut(), v);
    |                 ^^^^^^^^^^^^^---------------^^^^
@@ -194,7 +174,7 @@ LL |     let _a: A = ptr::replace(ptr::null_mut(), v);
    = help: for more information, visit <https://doc.rust-lang.org/std/ptr/index.html> and <https://doc.rust-lang.org/reference/behavior-considered-undefined.html>
 
 error: calling this function with a null pointer is undefined behavior, even if the result of the function is unused
-  --> $DIR/invalid_null_args.rs:69:5
+  --> $DIR/invalid_null_args.rs:68:5
    |
 LL |     ptr::swap::<A>(ptr::null_mut(), &mut v);
    |     ^^^^^^^^^^^^^^^---------------^^^^^^^^^
@@ -204,7 +184,7 @@ LL |     ptr::swap::<A>(ptr::null_mut(), &mut v);
    = help: for more information, visit <https://doc.rust-lang.org/std/ptr/index.html> and <https://doc.rust-lang.org/reference/behavior-considered-undefined.html>
 
 error: calling this function with a null pointer is undefined behavior, even if the result of the function is unused
-  --> $DIR/invalid_null_args.rs:71:5
+  --> $DIR/invalid_null_args.rs:70:5
    |
 LL |     ptr::swap::<A>(&mut v, ptr::null_mut());
    |     ^^^^^^^^^^^^^^^^^^^^^^^---------------^
@@ -214,7 +194,7 @@ LL |     ptr::swap::<A>(&mut v, ptr::null_mut());
    = help: for more information, visit <https://doc.rust-lang.org/std/ptr/index.html> and <https://doc.rust-lang.org/reference/behavior-considered-undefined.html>
 
 error: calling this function with a null pointer is undefined behavior, even if the result of the function is unused
-  --> $DIR/invalid_null_args.rs:74:5
+  --> $DIR/invalid_null_args.rs:73:5
    |
 LL |     ptr::swap_nonoverlapping::<A>(ptr::null_mut(), &mut v, 0);
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^---------------^^^^^^^^^^^^
@@ -224,7 +204,7 @@ LL |     ptr::swap_nonoverlapping::<A>(ptr::null_mut(), &mut v, 0);
    = help: for more information, visit <https://doc.rust-lang.org/std/ptr/index.html> and <https://doc.rust-lang.org/reference/behavior-considered-undefined.html>
 
 error: calling this function with a null pointer is undefined behavior, even if the result of the function is unused
-  --> $DIR/invalid_null_args.rs:76:5
+  --> $DIR/invalid_null_args.rs:75:5
    |
 LL |     ptr::swap_nonoverlapping::<A>(&mut v, ptr::null_mut(), 0);
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^---------------^^^^
@@ -234,7 +214,7 @@ LL |     ptr::swap_nonoverlapping::<A>(&mut v, ptr::null_mut(), 0);
    = help: for more information, visit <https://doc.rust-lang.org/std/ptr/index.html> and <https://doc.rust-lang.org/reference/behavior-considered-undefined.html>
 
 error: calling this function with a null pointer is undefined behavior, even if the result of the function is unused
-  --> $DIR/invalid_null_args.rs:79:5
+  --> $DIR/invalid_null_args.rs:78:5
    |
 LL |     ptr::write(ptr::null_mut(), v);
    |     ^^^^^^^^^^^---------------^^^^
@@ -244,7 +224,7 @@ LL |     ptr::write(ptr::null_mut(), v);
    = help: for more information, visit <https://doc.rust-lang.org/std/ptr/index.html> and <https://doc.rust-lang.org/reference/behavior-considered-undefined.html>
 
 error: calling this function with a null pointer is undefined behavior, even if the result of the function is unused
-  --> $DIR/invalid_null_args.rs:82:5
+  --> $DIR/invalid_null_args.rs:81:5
    |
 LL |     ptr::write_unaligned(ptr::null_mut(), v);
    |     ^^^^^^^^^^^^^^^^^^^^^---------------^^^^
@@ -254,17 +234,7 @@ LL |     ptr::write_unaligned(ptr::null_mut(), v);
    = help: for more information, visit <https://doc.rust-lang.org/std/ptr/index.html> and <https://doc.rust-lang.org/reference/behavior-considered-undefined.html>
 
 error: calling this function with a null pointer is undefined behavior, even if the result of the function is unused
-  --> $DIR/invalid_null_args.rs:85:5
-   |
-LL |     ptr::write_volatile(ptr::null_mut(), v);
-   |     ^^^^^^^^^^^^^^^^^^^^---------------^^^^
-   |                         |
-   |                         null pointer originates from here
-   |
-   = help: for more information, visit <https://doc.rust-lang.org/std/ptr/index.html> and <https://doc.rust-lang.org/reference/behavior-considered-undefined.html>
-
-error: calling this function with a null pointer is undefined behavior, even if the result of the function is unused
-  --> $DIR/invalid_null_args.rs:88:5
+  --> $DIR/invalid_null_args.rs:87:5
    |
 LL |     ptr::write_bytes::<usize>(ptr::null_mut(), 42, 0);
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^---------------^^^^^^^^
@@ -274,7 +244,7 @@ LL |     ptr::write_bytes::<usize>(ptr::null_mut(), 42, 0);
    = help: for more information, visit <https://doc.rust-lang.org/std/ptr/index.html> and <https://doc.rust-lang.org/reference/behavior-considered-undefined.html>
 
 error: calling this function with a null pointer is undefined behavior, even if the result of the function is unused
-  --> $DIR/invalid_null_args.rs:93:18
+  --> $DIR/invalid_null_args.rs:92:18
    |
 LL |     let _a: u8 = ptr::read(const_ptr);
    |                  ^^^^^^^^^^^^^^^^^^^^
@@ -287,7 +257,7 @@ LL |     let null_ptr = ptr::null_mut();
    |                    ^^^^^^^^^^^^^^^
 
 error: calling this function with a null pointer is undefined behavior, even if the result of the function is unused
-  --> $DIR/invalid_null_args.rs:100:5
+  --> $DIR/invalid_null_args.rs:99:5
    |
 LL |     std::slice::from_raw_parts::<()>(ptr::null(), 0);
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^-----------^^^^
@@ -297,7 +267,7 @@ LL |     std::slice::from_raw_parts::<()>(ptr::null(), 0);
    = help: for more information, visit <https://doc.rust-lang.org/std/ptr/index.html> and <https://doc.rust-lang.org/reference/behavior-considered-undefined.html>
 
 error: calling this function with a null pointer is undefined behavior, even if the result of the function is unused
-  --> $DIR/invalid_null_args.rs:102:5
+  --> $DIR/invalid_null_args.rs:101:5
    |
 LL |     std::slice::from_raw_parts::<Zst>(ptr::null(), 0);
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^-----------^^^^
@@ -307,7 +277,7 @@ LL |     std::slice::from_raw_parts::<Zst>(ptr::null(), 0);
    = help: for more information, visit <https://doc.rust-lang.org/std/ptr/index.html> and <https://doc.rust-lang.org/reference/behavior-considered-undefined.html>
 
 error: calling this function with a null pointer is undefined behavior, even if the result of the function is unused
-  --> $DIR/invalid_null_args.rs:104:5
+  --> $DIR/invalid_null_args.rs:103:5
    |
 LL |     std::slice::from_raw_parts_mut::<()>(ptr::null_mut(), 0);
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^---------------^^^^
@@ -317,7 +287,7 @@ LL |     std::slice::from_raw_parts_mut::<()>(ptr::null_mut(), 0);
    = help: for more information, visit <https://doc.rust-lang.org/std/ptr/index.html> and <https://doc.rust-lang.org/reference/behavior-considered-undefined.html>
 
 error: calling this function with a null pointer is undefined behavior, even if the result of the function is unused
-  --> $DIR/invalid_null_args.rs:106:5
+  --> $DIR/invalid_null_args.rs:105:5
    |
 LL |     std::slice::from_raw_parts_mut::<Zst>(ptr::null_mut(), 0);
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^---------------^^^^
@@ -326,5 +296,5 @@ LL |     std::slice::from_raw_parts_mut::<Zst>(ptr::null_mut(), 0);
    |
    = help: for more information, visit <https://doc.rust-lang.org/std/ptr/index.html> and <https://doc.rust-lang.org/reference/behavior-considered-undefined.html>
 
-error: aborting due to 31 previous errors
+error: aborting due to 28 previous errors
 

tests/ui/precondition-checks/read_volatile.rs

@@ -3,8 +3,6 @@
 //@ error-pattern: unsafe precondition(s) violated: ptr::read_volatile requires
 //@ revisions: misaligned
 
-#![allow(invalid_null_arguments)]
-
 use std::ptr;
 
 fn main() {