move IOV_MAX to limits header

src/header/limits/mod.rs

@@ -12,6 +12,13 @@ pub const PASS_MAX: usize = 128;
 pub const PATH_MAX: usize = 4096;
 pub const NGROUPS_MAX: usize = 65536;
 
+/// Maximum number of `iovec` structures that one process has available for
+/// use with `readv()` or `writev()`.
+pub const IOV_MAX: c_int = 1024;
+
+/// Minimum required value for `IOV_MAX`.
+pub const _XOPEN_IOV_MAX: c_int = 16;
+
 pub const CHAR_BIT: u32 = 8;
 pub const WORD_BIT: u32 = 32;
 #[cfg(target_pointer_width = "32")]

src/header/sys_uio/mod.rs

@@ -5,7 +5,7 @@
 use core::slice;
 
 use crate::{
-    header::{errno, unistd},
+    header::{errno, limits::IOV_MAX, unistd},
     platform::{
         self,
         types::{c_int, c_void, off_t, ssize_t},
@@ -14,8 +14,6 @@ use crate::{
 
 pub use crate::header::bits_iovec::{gather, iovec, scatter};
 
-pub const IOV_MAX: c_int = 1024;
-
 /// Non-POSIX, see <https://man7.org/linux/man-pages/man2/readv.2.html>.
 #[unsafe(no_mangle)]
 pub unsafe extern "C" fn preadv(

src/header/unistd/sysconf/linux.rs

@@ -10,7 +10,6 @@ use crate::{
     platform,
 };
 
-pub const _XOPEN_IOV_MAX: c_long = 16;
 pub const _XOPEN_NAME_MAX: c_long = 255;
 pub const _XOPEN_PATH_MAX: c_long = 1024;
 
@@ -192,7 +191,7 @@ pub(super) fn sysconf_impl(name: c_int) -> c_long {
         _SC_2_FORT_RUN => -1,
         _SC_2_SW_DEV => -1,
         _SC_2_LOCALEDEF => -1,
-        _SC_IOV_MAX => _XOPEN_IOV_MAX,
+        _SC_IOV_MAX => _XOPEN_IOV_MAX.into(),
         _SC_THREADS => _POSIX_VERSION,
         _SC_THREAD_SAFE_FUNCTIONS => _POSIX_VERSION,
         _SC_GETGR_R_SIZE_MAX => -1,