dangling_pointers_from_temporaries lint is imprecise (false positives and false negatives) #78691
Description
I tried this code:
use std::ffi::CString; extern "C" { fn gecko_profiler_register_thread(foo: *const std::os::raw::c_char); } pub fn main() { unsafe { gecko_profiler_register_thread(CString::new("foo").unwrap().as_ptr()); } }I get:
warning: getting the inner pointer of a temporary `CString` --> <source>:9:69 | 9 | gecko_profiler_register_thread(CString::new("foo").unwrap().as_ptr()); | ---------------------------- ^^^^^^ this pointer will be invalid | | | this `CString` is deallocated at the end of the statement, bind it to a variable to extend its lifetime | = note: `#[warn(temporary_cstring_as_ptr)]` on by default = note: pointers do not have a lifetime; when calling `as_ptr` the `CString` will be deallocated at the end of the statement because nothing is referencing it as far as the type system is concerned = help: for more information, see https://doc.rust-lang.org/reference/destructors.html warning: 1 warning emitted Compiler returned: 0 However since the CString is not deallocated until after the function call the code is fine and the warning should not trigger.
See https://rust.godbolt.org/z/vjrvGn for the assembly.