Updated the library to Rust 2024.

src/c/errno.rs

@@ -182,7 +182,7 @@ fn set_errno(errnum: i32)
 
 
 // The function to get the errno memory location.
-extern
+unsafe extern "C"
 {
    fn __errno_location() -> *mut CInt;
 }

src/c/math.rs

@@ -3,7 +3,7 @@ use binding::{CFloat, CDouble, CInt};
 
 // Taken from: https://en.wikipedia.org/wiki/C_mathematical_functions
 #[link(name="m")]
-extern
+unsafe extern "C"
 {
    // Basic functions.
    pub fn fabs(arg: CDouble) -> CDouble;

src/c/stdio.rs

@@ -8,7 +8,7 @@ pub enum FILE
 
 
 
-extern
+unsafe extern "C"
 {
    pub fn fileno(stream: *mut FILE) -> CInt;
    pub fn fopen(filename: *const CChar, mode: *const CChar) -> *mut FILE;

src/c/stdlib.rs

@@ -2,7 +2,7 @@ use binding::CVoid;
 
 
 #[link(name="c")]
-extern
+unsafe extern "C"
 {
    pub fn calloc(nobj: usize, size: usize) -> *mut CVoid;
    pub fn malloc(size: usize) -> *mut CVoid;

src/c/string.rs

@@ -5,7 +5,7 @@ use crate::stddef::{size_t, wchar_t};
 
 #[cfg(not(feature="no_mem_manip"))]
 #[link(name="c")]
-extern
+unsafe extern "C"
 {
    /// Copies the values of n bytes from the location pointed to by
    /// src directly to the memory block pointed to by dest.
@@ -56,7 +56,7 @@ extern
 }
 
 #[link(name="c")]
-extern
+unsafe extern "C"
 {
    pub fn strcpy(dst: *mut CChar, src: *const CChar) -> *mut CChar;
    pub fn strncpy(dst: *mut CChar, src: *const CChar,

src/c/time.rs

@@ -46,7 +46,7 @@ pub struct LocalTime
 
 
 #[link(name="c")]
-extern
+unsafe extern "C"
 {
    /// Uses the value pointed by time to fill a LocalTime structure with
    /// the values that represent the corresponding time, expressed