Apply weak attributes to all intrinsics

Removed the `weak-intrinsics` feature, so that all functions
will have the `weak` linkage attribute.

Also this fixed the bug in
rust-lang/rust#124042.

Before this commit, generated code will be
```rust
pub extern "C" fn <name>(...) -> ... {
        // code...
}
pub mod <name> {
    #[linkage = "weak"]
    #[no_mangle]
    pub extern "C" fn <name>(...) -> ... {
        super::<name>(...)
    }
}
```

The issue is that there is 2 `weak` linkage, the first one is not required.
Along refactoring `weak` attributes, this was fixed.

Author: Amjad50

src/arm.rs

@@ -20,7 +20,6 @@ macro_rules! bl {
 intrinsics! {
     // NOTE This function and the ones below are implemented using assembly because they are using a
     // custom calling convention which can't be implemented using a normal Rust function.
-    #[cfg_attr(all(not(windows), not(target_vendor="apple")), weak)]
     #[naked]
     #[cfg(not(target_env = "msvc"))]
     pub unsafe extern "C" fn __aeabi_uidivmod() {
@@ -36,7 +35,6 @@ intrinsics! {
         );
     }
 
-    #[cfg_attr(all(not(windows), not(target_vendor="apple")), weak)]
     #[naked]
     pub unsafe extern "C" fn __aeabi_uldivmod() {
         core::arch::asm!(
@@ -53,7 +51,6 @@ intrinsics! {
         );
     }
 
-    #[cfg_attr(all(not(windows), not(target_vendor="apple")), weak)]
     #[naked]
     pub unsafe extern "C" fn __aeabi_idivmod() {
         core::arch::asm!(
@@ -67,7 +64,6 @@ intrinsics! {
         );
     }
 
-    #[cfg_attr(all(not(windows), not(target_vendor="apple")), weak)]
     #[naked]
     pub unsafe extern "C" fn __aeabi_ldivmod() {
         core::arch::asm!(
@@ -84,17 +80,13 @@ intrinsics! {
         );
     }
 
-    // The following functions use weak linkage to allow users to override
-    // with custom implementation.
     // FIXME: The `*4` and `*8` variants should be defined as aliases.
 
-    #[weak]
     #[cfg(not(target_os = "ios"))]
     pub unsafe extern "aapcs" fn __aeabi_memcpy(dest: *mut u8, src: *const u8, n: usize) {
         crate::mem::memcpy(dest, src, n);
     }
 
-    #[weak]
     #[cfg(not(target_os = "ios"))]
     pub unsafe extern "aapcs" fn __aeabi_memcpy4(dest: *mut u8, src: *const u8, n: usize) {
         // We are guaranteed 4-alignment, so accessing at u32 is okay.
@@ -112,38 +104,32 @@ intrinsics! {
         __aeabi_memcpy(dest as *mut u8, src as *const u8, n);
     }
 
-    #[weak]
     #[cfg(not(target_os = "ios"))]
     pub unsafe extern "aapcs" fn __aeabi_memcpy8(dest: *mut u8, src: *const u8, n: usize) {
         __aeabi_memcpy4(dest, src, n);
     }
 
-    #[weak]
     #[cfg(not(target_os = "ios"))]
     pub unsafe extern "aapcs" fn __aeabi_memmove(dest: *mut u8, src: *const u8, n: usize) {
         crate::mem::memmove(dest, src, n);
     }
 
-    #[weak]
     #[cfg(not(any(target_os = "ios", target_env = "msvc")))]
     pub unsafe extern "aapcs" fn __aeabi_memmove4(dest: *mut u8, src: *const u8, n: usize) {
         __aeabi_memmove(dest, src, n);
     }
 
-    #[weak]
     #[cfg(not(any(target_os = "ios", target_env = "msvc")))]
     pub unsafe extern "aapcs" fn __aeabi_memmove8(dest: *mut u8, src: *const u8, n: usize) {
         __aeabi_memmove(dest, src, n);
     }
 
-    #[weak]
     #[cfg(not(target_os = "ios"))]
     pub unsafe extern "aapcs" fn __aeabi_memset(dest: *mut u8, n: usize, c: i32) {
         // Note the different argument order
         crate::mem::memset(dest, c, n);
     }
 
-    #[weak]
     #[cfg(not(target_os = "ios"))]
     pub unsafe extern "aapcs" fn __aeabi_memset4(dest: *mut u8, n: usize, c: i32) {
         let mut dest = dest as *mut u32;
@@ -161,25 +147,21 @@ intrinsics! {
         __aeabi_memset(dest as *mut u8, n, byte as i32);
     }
 
-    #[weak]
     #[cfg(not(target_os = "ios"))]
     pub unsafe extern "aapcs" fn __aeabi_memset8(dest: *mut u8, n: usize, c: i32) {
         __aeabi_memset4(dest, n, c);
     }
 
-    #[weak]
     #[cfg(not(target_os = "ios"))]
     pub unsafe extern "aapcs" fn __aeabi_memclr(dest: *mut u8, n: usize) {
         __aeabi_memset(dest, n, 0);
     }
 
-    #[weak]
     #[cfg(not(any(target_os = "ios", target_env = "msvc")))]
     pub unsafe extern "aapcs" fn __aeabi_memclr4(dest: *mut u8, n: usize) {
         __aeabi_memset4(dest, n, 0);
     }
 
-    #[weak]
     #[cfg(not(any(target_os = "ios", target_env = "msvc")))]
     pub unsafe extern "aapcs" fn __aeabi_memclr8(dest: *mut u8, n: usize) {
         __aeabi_memset4(dest, n, 0);

src/macros.rs

@@ -25,11 +25,14 @@ macro_rules! public_test_dep {
 /// platforms need and elsewhere in this library it just looks like normal Rust
 /// code.
 ///
-/// When the weak-intrinsics feature is enabled, all intrinsics functions are
-/// marked with #[linkage = "weak"] so that they can be replaced by another
-/// implementation at link time. This is particularly useful for mixed Rust/C++
-/// binaries that want to use the C++ intrinsics, otherwise linking against the
-/// Rust stdlib will replace those from the compiler-rt library.
+/// All intrinsics functions are marked with #[linkage = "weak"] when
+/// `not(windows) and not(target_vendor = "apple")` except `mem` intrinsics, which
+/// will only have the `#[linkage = "weak"]` attribute when the `mem-weak-intrinsics`
+/// feature is enabled.
+/// `weak` linkage attribute is used so that these functions can be replaced
+/// by another implementation at link time. This is particularly useful for mixed
+/// Rust/C++ binaries that want to use the C++ intrinsics, otherwise linking against
+/// the Rust stdlib will replace those from the compiler-rt library.
 ///
 /// This macro is structured to be invoked with a bunch of functions that looks
 /// like:
@@ -53,10 +56,6 @@ macro_rules! public_test_dep {
 ///
 /// A quick overview of attributes supported right now are:
 ///
-/// * `weak` - indicates that the function should always be given weak linkage.
-///   This attribute must come before other attributes, as the other attributes
-///   will generate the final output function and need to have `weak` modify
-///   them.
 /// * `maybe_use_optimized_c_shim` - indicates that the Rust implementation is
 ///   ignored if an optimized C version was compiled.
 /// * `aapcs_on_arm` - forces the ABI of the function to be `"aapcs"` on ARM and
@@ -128,67 +127,6 @@ macro_rules! intrinsics {
         intrinsics!($($rest)*);
     );
 
-    // Explicit weak linkage gets dropped when weak-intrinsics is on since it
-    // will be added unconditionally to all intrinsics and would conflict
-    // otherwise.
-    (
-        #[weak]
-        $(#[$($attr:tt)*])*
-        pub extern $abi:tt fn $name:ident( $($argname:ident:  $ty:ty),* ) $(-> $ret:ty)? {
-            $($body:tt)*
-        }
-
-        $($rest:tt)*
-    ) => (
-        #[cfg(feature = "weak-intrinsics")]
-        intrinsics! {
-            $(#[$($attr)*])*
-            pub extern $abi fn $name( $($argname: $ty),* ) $(-> $ret)? {
-                $($body)*
-            }
-        }
-
-        #[cfg(not(feature = "weak-intrinsics"))]
-        intrinsics! {
-            $(#[$($attr)*])*
-            #[linkage = "weak"]
-            pub extern $abi fn $name( $($argname: $ty),* ) $(-> $ret)? {
-                $($body)*
-            }
-        }
-
-        intrinsics!($($rest)*);
-    );
-    // Same as above but for unsafe.
-    (
-        #[weak]
-        $(#[$($attr:tt)*])*
-        pub unsafe extern $abi:tt fn $name:ident( $($argname:ident:  $ty:ty),* ) $(-> $ret:ty)? {
-            $($body:tt)*
-        }
-
-        $($rest:tt)*
-    ) => (
-        #[cfg(feature = "weak-intrinsics")]
-        intrinsics! {
-            $(#[$($attr)*])*
-            pub unsafe extern $abi fn $name( $($argname: $ty),* ) $(-> $ret)? {
-                $($body)*
-            }
-        }
-
-        #[cfg(not(feature = "weak-intrinsics"))]
-        intrinsics! {
-            $(#[$($attr)*])*
-            #[linkage = "weak"]
-            pub unsafe extern $abi fn $name( $($argname: $ty),* ) $(-> $ret)? {
-                $($body)*
-            }
-        }
-
-        intrinsics!($($rest)*);
-    );
-
     // Right now there's a bunch of architecture-optimized intrinsics in the
     // stock compiler-rt implementation. Not all of these have been ported over
     // to Rust yet so when the `c` feature of this crate is enabled we fall back
@@ -211,7 +149,7 @@ macro_rules! intrinsics {
         $($rest:tt)*
     ) => (
         #[cfg($name = "optimized-c")]
-        #[cfg_attr(feature = "weak-intrinsics", linkage = "weak")]
+        #[cfg_attr(all(not(windows), not(target_vendor = "apple")), linkage = "weak")]
         pub $(unsafe $($empty)? )? extern $abi fn $name( $($argname: $ty),* ) $(-> $ret)? {
             extern $abi {
                 fn $name($($argname: $ty),*) $(-> $ret)?;
@@ -311,15 +249,14 @@ macro_rules! intrinsics {
     ) => (
         #[cfg(all(any(windows, target_os = "uefi"), target_arch = "x86_64"))]
         $(#[$($attr)*])*
-        #[cfg_attr(feature = "weak-intrinsics", linkage = "weak")]
         pub extern $abi fn $name( $($argname: $ty),* ) $(-> $ret)? {
             $($body)*
         }
 
         #[cfg(all(any(windows, target_os = "uefi"), target_arch = "x86_64"))]
         pub mod $name {
             #[cfg_attr(not(feature = "mangled-names"), no_mangle)]
-            #[cfg_attr(feature = "weak-intrinsics", linkage = "weak")]
+            #[cfg_attr(all(not(windows), not(target_vendor = "apple")), linkage = "weak")]
             pub extern $abi fn $name( $($argname: $ty),* )
                 -> $crate::macros::win64_128bit_abi_hack::U64x2
             {
@@ -360,7 +297,7 @@ macro_rules! intrinsics {
         #[cfg(target_arch = "arm")]
         pub mod $name {
             #[cfg_attr(not(feature = "mangled-names"), no_mangle)]
-            #[cfg_attr(feature = "weak-intrinsics", linkage = "weak")]
+            #[cfg_attr(all(not(windows), not(target_vendor = "apple")), linkage = "weak")]
             pub extern $abi fn $name( $($argname: $ty),* ) $(-> $ret)? {
                 super::$name($($argname),*)
             }
@@ -369,7 +306,7 @@ macro_rules! intrinsics {
         #[cfg(target_arch = "arm")]
         pub mod $alias {
             #[cfg_attr(not(feature = "mangled-names"), no_mangle)]
-            #[cfg_attr(any(all(not(windows), not(target_vendor="apple")), feature = "weak-intrinsics"), linkage = "weak")]
+            #[cfg_attr(all(not(windows), not(target_vendor="apple")), linkage = "weak")]
             pub extern "aapcs" fn $alias( $($argname: $ty),* ) $(-> $ret)? {
                 super::$name($($argname),*)
             }
@@ -405,7 +342,7 @@ macro_rules! intrinsics {
         pub mod $name {
             $(#[$($attr)*])*
             #[cfg_attr(not(feature = "mangled-names"), no_mangle)]
-            #[cfg_attr(feature = "weak-intrinsics", linkage = "weak")]
+            #[cfg_attr(all(not(windows), not(target_vendor = "apple"), not(target_env = "gnu"), feature = "mem-weak-intrinsics"), linkage = "weak")]
             pub unsafe extern $abi fn $name( $($argname: $ty),* ) $(-> $ret)? {
                 super::$name($($argname),*)
             }
@@ -429,7 +366,7 @@ macro_rules! intrinsics {
             #[naked]
             $(#[$($attr)*])*
             #[cfg_attr(not(feature = "mangled-names"), no_mangle)]
-            #[cfg_attr(feature = "weak-intrinsics", linkage = "weak")]
+            #[cfg_attr(all(not(windows), not(target_vendor = "apple")), linkage = "weak")]
             pub unsafe extern $abi fn $name( $($argname: $ty),* ) $(-> $ret)? {
                 $($body)*
             }
@@ -495,7 +432,7 @@ macro_rules! intrinsics {
         pub mod $name {
             $(#[$($attr)*])*
             #[cfg_attr(not(feature = "mangled-names"), no_mangle)]
-            #[cfg_attr(feature = "weak-intrinsics", linkage = "weak")]
+            #[cfg_attr(all(not(windows), not(target_vendor = "apple")), linkage = "weak")]
             pub extern $abi fn $name( $($argname: $ty),* ) $(-> $ret)? {
                 super::$name($($argname),*)
             }
@@ -521,7 +458,7 @@ macro_rules! intrinsics {
         pub mod $name {
             $(#[$($attr)*])*
             #[cfg_attr(not(feature = "mangled-names"), no_mangle)]
-            #[cfg_attr(feature = "weak-intrinsics", linkage = "weak")]
+            #[cfg_attr(all(not(windows), not(target_vendor = "apple")), linkage = "weak")]
             pub unsafe extern $abi fn $name( $($argname: $ty),* ) $(-> $ret)? {
                 super::$name($($argname),*)
             }

src/math.rs

@@ -7,7 +7,6 @@ macro_rules! no_mangle {
     ($(fn $fun:ident($($iid:ident : $ity:ty),+) -> $oty:ty;)+) => {
         intrinsics! {
             $(
-                #[cfg_attr(all(not(windows), not(target_vendor = "apple")), weak)]
                 pub extern "C" fn $fun($($iid: $ity),+) -> $oty {
                     self::libm::$fun($($iid),+)
                 }
@@ -92,14 +91,12 @@ no_mangle! {
 }
 
 intrinsics! {
-    #[cfg_attr(all(not(windows), not(target_vendor = "apple")), weak)]
     pub extern "C" fn lgamma_r(x: f64, s: &mut i32) -> f64 {
         let r = self::libm::lgamma_r(x);
         *s = r.1;
         r.0
     }
 
-    #[cfg_attr(all(not(windows), not(target_vendor = "apple")), weak)]
     pub extern "C" fn lgammaf_r(x: f32, s: &mut i32) -> f32 {
         let r = self::libm::lgammaf_r(x);
         *s = r.1;

src/mem/mod.rs

@@ -20,14 +20,12 @@ use core::ops::{BitOr, Shl};
 mod impls;
 
 intrinsics! {
-    #[cfg_attr(not(all(target_os = "windows", target_env = "gnu")), weak)]
     #[mem_builtin]
     pub unsafe extern "C" fn memcpy(dest: *mut u8, src: *const u8, n: usize) -> *mut u8 {
         impls::copy_forward(dest, src, n);
         dest
     }
 
-    #[cfg_attr(not(all(target_os = "windows", target_env = "gnu")), weak)]
     #[mem_builtin]
     pub unsafe extern "C" fn memmove(dest: *mut u8, src: *const u8, n: usize) -> *mut u8 {
         let delta = (dest as usize).wrapping_sub(src as usize);
@@ -41,26 +39,22 @@ intrinsics! {
         dest
     }
 
-    #[cfg_attr(not(all(target_os = "windows", target_env = "gnu")), weak)]
     #[mem_builtin]
     pub unsafe extern "C" fn memset(s: *mut u8, c: crate::mem::c_int, n: usize) -> *mut u8 {
         impls::set_bytes(s, c as u8, n);
         s
     }
 
-    #[cfg_attr(not(all(target_os = "windows", target_env = "gnu")), weak)]
     #[mem_builtin]
     pub unsafe extern "C" fn memcmp(s1: *const u8, s2: *const u8, n: usize) -> i32 {
         impls::compare_bytes(s1, s2, n)
     }
 
-    #[cfg_attr(not(all(target_os = "windows", target_env = "gnu")), weak)]
     #[mem_builtin]
     pub unsafe extern "C" fn bcmp(s1: *const u8, s2: *const u8, n: usize) -> i32 {
         memcmp(s1, s2, n)
     }
 
-    #[cfg_attr(not(all(target_os = "windows", target_env = "gnu")), weak)]
     #[mem_builtin]
     pub unsafe extern "C" fn strlen(s: *const core::ffi::c_char) -> usize {
         impls::c_string_length(s)