Change the syntax of the internal weak! macro

madsmtm · madsmtm · commit a7bafc0afc3d · 2025-03-26T16:25:05.000+01:00
Change the syntax to include parameter names and a trailing semicolon.

Motivation:
- Mirror the `syscall!` macro.
- Allow rustfmt to format it (when wrapped in parentheses).
- For better documentation (having the parameter names available in
  the source code is a bit nicer).
- Allow future improvements to this macro where we can sometimes use the
  symbol directly when it's statically known to be available.
diff --git a/library/std/src/sys/fs/unix.rs b/library/std/src/sys/fs/unix.rs
@@ -155,15 +155,15 @@ cfg_has_statx! {{
         enum STATX_STATE{ Unknown = 0, Present, Unavailable }
         static STATX_SAVED_STATE: AtomicU8 = AtomicU8::new(STATX_STATE::Unknown as u8);
 
-        syscall! {
+        syscall!(
             fn statx(
                 fd: c_int,
                 pathname: *const c_char,
                 flags: c_int,
                 mask: libc::c_uint,
-                statxbuf: *mut libc::statx
-            ) -> c_int
-        }
+                statxbuf: *mut libc::statx,
+            ) -> c_int;
+        );
 
         let statx_availability = STATX_SAVED_STATE.load(Ordering::Relaxed);
         if statx_availability == STATX_STATE::Unavailable as u8 {
@@ -1540,7 +1540,9 @@ impl File {
                 let times = [to_timespec(times.accessed)?, to_timespec(times.modified)?];
                 // futimens requires Android API level 19
                 cvt(unsafe {
-                    weak!(fn futimens(c_int, *const libc::timespec) -> c_int);
+                    weak!(
+                        fn futimens(fd: c_int, times: *const libc::timespec) -> c_int;
+                    );
                     match futimens.get() {
                         Some(futimens) => futimens(self.as_raw_fd(), times.as_ptr()),
                         None => return Err(io::const_error!(
@@ -1556,7 +1558,9 @@ impl File {
                     use crate::sys::{time::__timespec64, weak::weak};
 
                     // Added in glibc 2.34
-                    weak!(fn __futimens64(libc::c_int, *const __timespec64) -> libc::c_int);
+                    weak!(
+                        fn __futimens64(fd: c_int, times: *const __timespec64) -> c_int;
+                    );
 
                     if let Some(futimens64) = __futimens64.get() {
                         let to_timespec = |time: Option<SystemTime>| time.map(|time| time.t.to_timespec64())
diff --git a/library/std/src/sys/pal/unix/fd.rs b/library/std/src/sys/pal/unix/fd.rs
@@ -232,14 +232,14 @@ impl FileDesc {
     // implementation if `preadv` is not available.
     #[cfg(all(target_os = "android", target_pointer_width = "64"))]
     pub fn read_vectored_at(&self, bufs: &mut [IoSliceMut<'_>], offset: u64) -> io::Result<usize> {
-        super::weak::syscall! {
+        super::weak::syscall!(
             fn preadv(
                 fd: libc::c_int,
                 iovec: *const libc::iovec,
                 n_iovec: libc::c_int,
-                offset: off64_t
-            ) -> isize
-        }
+                offset: off64_t,
+            ) -> isize;
+        );
 
         let ret = cvt(unsafe {
             preadv(
@@ -257,7 +257,14 @@ impl FileDesc {
     // and its metadata from LLVM IR.
     #[no_sanitize(cfi)]
     pub fn read_vectored_at(&self, bufs: &mut [IoSliceMut<'_>], offset: u64) -> io::Result<usize> {
-        super::weak::weak!(fn preadv64(libc::c_int, *const libc::iovec, libc::c_int, off64_t) -> isize);
+        super::weak::weak!(
+            fn preadv64(
+                fd: libc::c_int,
+                iovec: *const libc::iovec,
+                n_iovec: libc::c_int,
+                offset: off64_t,
+            ) -> isize;
+        );
 
         match preadv64.get() {
             Some(preadv) => {
@@ -286,7 +293,14 @@ impl FileDesc {
     // use "weak" linking.
     #[cfg(target_vendor = "apple")]
     pub fn read_vectored_at(&self, bufs: &mut [IoSliceMut<'_>], offset: u64) -> io::Result<usize> {
-        super::weak::weak!(fn preadv(libc::c_int, *const libc::iovec, libc::c_int, off64_t) -> isize);
+        super::weak::weak!(
+            fn preadv(
+                fd: libc::c_int,
+                iovec: *const libc::iovec,
+                n_iovec: libc::c_int,
+                offset: off64_t,
+            ) -> isize;
+        );
 
         match preadv.get() {
             Some(preadv) => {
@@ -428,14 +442,14 @@ impl FileDesc {
     // implementation if `pwritev` is not available.
     #[cfg(all(target_os = "android", target_pointer_width = "64"))]
     pub fn write_vectored_at(&self, bufs: &[IoSlice<'_>], offset: u64) -> io::Result<usize> {
-        super::weak::syscall! {
+        super::weak::syscall!(
             fn pwritev(
                 fd: libc::c_int,
                 iovec: *const libc::iovec,
                 n_iovec: libc::c_int,
-                offset: off64_t
-            ) -> isize
-        }
+                offset: off64_t,
+            ) -> isize;
+        );
 
         let ret = cvt(unsafe {
             pwritev(
@@ -450,7 +464,14 @@ impl FileDesc {
 
     #[cfg(all(target_os = "android", target_pointer_width = "32"))]
     pub fn write_vectored_at(&self, bufs: &[IoSlice<'_>], offset: u64) -> io::Result<usize> {
-        super::weak::weak!(fn pwritev64(libc::c_int, *const libc::iovec, libc::c_int, off64_t) -> isize);
+        super::weak::weak!(
+            fn pwritev64(
+                fd: libc::c_int,
+                iovec: *const libc::iovec,
+                n_iovec: libc::c_int,
+                offset: off64_t,
+            ) -> isize;
+        );
 
         match pwritev64.get() {
             Some(pwritev) => {
@@ -479,7 +500,14 @@ impl FileDesc {
     // use "weak" linking.
     #[cfg(target_vendor = "apple")]
     pub fn write_vectored_at(&self, bufs: &[IoSlice<'_>], offset: u64) -> io::Result<usize> {
-        super::weak::weak!(fn pwritev(libc::c_int, *const libc::iovec, libc::c_int, off64_t) -> isize);
+        super::weak::weak!(
+            fn pwritev(
+                fd: libc::c_int,
+                iovec: *const libc::iovec,
+                n_iovec: libc::c_int,
+                offset: off64_t,
+            ) -> isize;
+        );
 
         match pwritev.get() {
             Some(pwritev) => {
diff --git a/library/std/src/sys/pal/unix/kernel_copy.rs b/library/std/src/sys/pal/unix/kernel_copy.rs
@@ -604,16 +604,16 @@ pub(super) fn copy_regular_files(reader: RawFd, writer: RawFd, max_len: u64) ->
         _ => true,
     };
 
-    syscall! {
+    syscall!(
         fn copy_file_range(
             fd_in: libc::c_int,
             off_in: *mut libc::loff_t,
             fd_out: libc::c_int,
             off_out: *mut libc::loff_t,
             len: libc::size_t,
-            flags: libc::c_uint
-        ) -> libc::ssize_t
-    }
+            flags: libc::c_uint,
+        ) -> libc::ssize_t;
+    );
 
     fn probe_copy_file_range_support() -> u8 {
         // In some cases, we cannot determine availability from the first
@@ -727,16 +727,16 @@ fn sendfile_splice(mode: SpliceMode, reader: RawFd, writer: RawFd, len: u64) ->
     // Android builds use feature level 14, but the libc wrapper for splice is
     // gated on feature level 21+, so we have to invoke the syscall directly.
     #[cfg(target_os = "android")]
-    syscall! {
+    syscall!(
         fn splice(
             srcfd: libc::c_int,
             src_offset: *const i64,
             dstfd: libc::c_int,
             dst_offset: *const i64,
             len: libc::size_t,
-            flags: libc::c_int
-        ) -> libc::ssize_t
-    }
+            flags: libc::c_int,
+        ) -> libc::ssize_t;
+    );
 
     #[cfg(target_os = "linux")]
     use libc::splice;
diff --git a/library/std/src/sys/pal/unix/stack_overflow.rs b/library/std/src/sys/pal/unix/stack_overflow.rs
@@ -424,18 +424,32 @@ mod imp {
 
         let pages = PAGES.get_or_init(|| {
             use crate::sys::weak::dlsym;
-            dlsym!(fn sysctlbyname(*const libc::c_char, *mut libc::c_void, *mut libc::size_t, *const libc::c_void, libc::size_t) -> libc::c_int);
+            dlsym!(
+                fn sysctlbyname(
+                    name: *const libc::c_char,
+                    oldp: *mut libc::c_void,
+                    oldlenp: *mut libc::size_t,
+                    newp: *const libc::c_void,
+                    newlen: libc::size_t,
+                ) -> libc::c_int;
+            );
             let mut guard: usize = 0;
             let mut size = size_of_val(&guard);
             let oid = c"security.bsd.stack_guard_page";
             match sysctlbyname.get() {
-                Some(fcn) if unsafe {
-                    fcn(oid.as_ptr(),
-                        (&raw mut guard).cast(),
-                        &raw mut size,
-                        ptr::null_mut(),
-                        0) == 0
-                } => guard,
+                Some(fcn)
+                    if unsafe {
+                        fcn(
+                            oid.as_ptr(),
+                            (&raw mut guard).cast(),
+                            &raw mut size,
+                            ptr::null_mut(),
+                            0,
+                        ) == 0
+                    } =>
+                {
+                    guard
+                }
                 _ => 1,
             }
         });
diff --git a/library/std/src/sys/pal/unix/thread.rs b/library/std/src/sys/pal/unix/thread.rs
@@ -193,11 +193,12 @@ impl Thread {
     // and its metadata from LLVM IR.
     #[no_sanitize(cfi)]
     pub fn set_name(name: &CStr) {
-        weak! {
+        weak!(
             fn pthread_setname_np(
-                libc::pthread_t, *const libc::c_char
-            ) -> libc::c_int
-        }
+                thread: libc::pthread_t,
+                name: *const libc::c_char,
+            ) -> libc::c_int;
+        );
 
         if let Some(f) = pthread_setname_np.get() {
             #[cfg(target_os = "nto")]
@@ -762,7 +763,9 @@ unsafe fn min_stack_size(attr: *const libc::pthread_attr_t) -> usize {
     // We use dlsym to avoid an ELF version dependency on GLIBC_PRIVATE. (#23628)
     // We shouldn't really be using such an internal symbol, but there's currently
     // no other way to account for the TLS size.
-    dlsym!(fn __pthread_get_minstack(*const libc::pthread_attr_t) -> libc::size_t);
+    dlsym!(
+        fn __pthread_get_minstack(attr: *const libc::pthread_attr_t) -> libc::size_t;
+    );
 
     match __pthread_get_minstack.get() {
         None => libc::PTHREAD_STACK_MIN,
diff --git a/library/std/src/sys/pal/unix/time.rs b/library/std/src/sys/pal/unix/time.rs
@@ -123,7 +123,12 @@ impl Timespec {
 
             // __clock_gettime64 was added to 32-bit arches in glibc 2.34,
             // and it handles both vDSO calls and ENOSYS fallbacks itself.
-            weak!(fn __clock_gettime64(libc::clockid_t, *mut __timespec64) -> libc::c_int);
+            weak!(
+                fn __clock_gettime64(
+                    clockid: libc::clockid_t,
+                    tp: *mut __timespec64,
+                ) -> libc::c_int;
+            );
 
             if let Some(clock_gettime64) = __clock_gettime64.get() {
                 let mut t = MaybeUninit::uninit();
diff --git a/library/std/src/sys/pal/unix/weak.rs b/library/std/src/sys/pal/unix/weak.rs
@@ -29,7 +29,7 @@ use crate::{mem, ptr};
 // We can use true weak linkage on ELF targets.
 #[cfg(all(unix, not(target_vendor = "apple")))]
 pub(crate) macro weak {
-    (fn $name:ident($($t:ty),*) -> $ret:ty) => (
+    (fn $name:ident($($param:ident : $t:ty),* $(,)?) -> $ret:ty;) => (
         let ref $name: ExternWeak<unsafe extern "C" fn($($t),*) -> $ret> = {
             unsafe extern "C" {
                 #[linkage = "extern_weak"]
@@ -62,10 +62,16 @@ impl<F: Copy> ExternWeak<F> {
 }
 
 pub(crate) macro dlsym {
-    (fn $name:ident($($t:ty),*) -> $ret:ty) => (
-         dlsym!(fn $name($($t),*) -> $ret, stringify!($name));
+    (fn $name:ident($($param:ident : $t:ty),* $(,)?) -> $ret:ty;) => (
+         dlsym!(
+            #[link_name = stringify!($name)]
+            fn $name($($param : $t),*) -> $ret;
+        );
     ),
-    (fn $name:ident($($t:ty),*) -> $ret:ty, $sym:expr) => (
+    (
+        #[link_name = $sym:expr]
+        fn $name:ident($($param:ident : $t:ty),* $(,)?) -> $ret:ty;
+    ) => (
         static DLSYM: DlsymWeak<unsafe extern "C" fn($($t),*) -> $ret> =
             DlsymWeak::new(concat!($sym, '\0'));
         let $name = &DLSYM;
@@ -143,15 +149,15 @@ unsafe fn fetch(name: &str) -> *mut libc::c_void {
 
 #[cfg(not(any(target_os = "linux", target_os = "android")))]
 pub(crate) macro syscall {
-    (fn $name:ident($($arg_name:ident: $t:ty),*) -> $ret:ty) => (
+    (fn $name:ident($($param:ident : $t:ty),* $(,)?) -> $ret:ty;) => (
         // FIXME(#115199): Rust currently omits weak function definitions
         // and its metadata from LLVM IR.
         #[no_sanitize(cfi)]
-        unsafe fn $name($($arg_name: $t),*) -> $ret {
-            weak! { fn $name($($t),*) -> $ret }
+        unsafe fn $name($($param: $t),*) -> $ret {
+            weak!(fn $name($($param: $t),*) -> $ret;);
 
             if let Some(fun) = $name.get() {
-                fun($($arg_name),*)
+                fun($($param),*)
             } else {
                 super::os::set_errno(libc::ENOSYS);
                 -1
@@ -162,26 +168,28 @@ pub(crate) macro syscall {
 
 #[cfg(any(target_os = "linux", target_os = "android"))]
 pub(crate) macro syscall {
-    (fn $name:ident($($arg_name:ident: $t:ty),*) -> $ret:ty) => (
-        unsafe fn $name($($arg_name:$t),*) -> $ret {
-            weak! { fn $name($($t),*) -> $ret }
+    (
+        fn $name:ident($($param:ident : $t:ty),* $(,)?) -> $ret:ty;
+    ) => (
+        unsafe fn $name($($param: $t),*) -> $ret {
+            weak!(fn $name($($param: $t),*) -> $ret;);
 
             // Use a weak symbol from libc when possible, allowing `LD_PRELOAD`
             // interposition, but if it's not found just use a raw syscall.
             if let Some(fun) = $name.get() {
-                fun($($arg_name),*)
+                fun($($param),*)
             } else {
-                libc::syscall(libc::${concat(SYS_, $name)}, $($arg_name),*) as $ret
+                libc::syscall(libc::${concat(SYS_, $name)}, $($param),*) as $ret
             }
         }
     )
 }
 
 #[cfg(any(target_os = "linux", target_os = "android"))]
 pub(crate) macro raw_syscall {
-    (fn $name:ident($($arg_name:ident: $t:ty),*) -> $ret:ty) => (
-        unsafe fn $name($($arg_name:$t),*) -> $ret {
-            libc::syscall(libc::${concat(SYS_, $name)}, $($arg_name),*) as $ret
+    (fn $name:ident($($param:ident : $t:ty),* $(,)?) -> $ret:ty;) => (
+        unsafe fn $name($($param: $t),*) -> $ret {
+            libc::syscall(libc::${concat(SYS_, $name)}, $($param),*) as $ret
         }
     )
 }
diff --git a/library/std/src/sys/process/unix/unix.rs b/library/std/src/sys/process/unix/unix.rs
diff --git a/library/std/src/sys/random/linux.rs b/library/std/src/sys/random/linux.rs
