warning: `malloc2` redeclares `malloc` with a different signature
  --> $DIR/issue-5791.rs:9:5
   |
LL | /     #[link_name = "malloc"]
LL | |     fn malloc1(len: i32) -> *const u8;
   | |______________________________________- `malloc` previously declared here
LL | /     #[link_name = "malloc"]
LL | |
LL | |     fn malloc2(len: i32, foo: i32) -> *const u8;
   | |________________________________________________^ this signature doesn't match the previous declaration
   |
note: the lint level is defined here
  --> $DIR/issue-5791.rs:3:9
   |
LL | #![warn(clashing_extern_declarations)]
   |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
   = note: expected `unsafe extern "C" fn(i32) -> *const u8`
              found `unsafe extern "C" fn(i32, i32) -> *const u8`

warning: 1 warning emitted