fix: fix differing bitwidth routines in win x86 gnu

Until #5032, whenever `libc` was running under Windows x86
with GNU, the default bit-width of `time_t` values was 32-bits. This
doesn't quite align with the defaults in MSVC and `mingw`, but that's
been addressed in that PR.

This PR is a quick patch for stable, as the changes in
#5032 are not backwards-compatible. It separates the
routines that under Windows use `time_t` values and changes their
link-time symbols to the 32-bit variants exposed in both MSVC and
`mingw`, for the affected target platform/environment.

It also adds a test, akin to the one in #5032, that should
ensure the correct bit-widths are in use for both the types and the
linked routine symbols.

Author: dybucc

libc-test/tests/windows_time.rs

@@ -0,0 +1,26 @@
+//! Ensures Windows `time`-related routines align with `libc`'s interface. By
+//! default, both MSVC and GNU (under `mingw`) expose 64-bit symbols, but in
+//! stable we need to cope with a 32-bit `time-t`, so the routines should link
+//! to their 32-bit variants.
+
+#![cfg(windows)]
+
+/// Ensures a 64-bit write is performed on values that should always be 64 bits,
+/// and that a corresponding 32-bit write is performed on values that should be
+/// 32 bits. This basically makes sure `time_t`'s bit-width aligns with those of
+/// functions that expect it as a parameter.
+#[test]
+fn test_bitwidth_store() {
+    #[cfg(all(target_arch = "x86", target_env = "gnu"))]
+    assert_eq!(size_of::<libc::time_t>(), 4);
+    #[cfg(not(all(target_arch = "x86", target_env = "gnu")))]
+    assert_eq!(size_of::<libc::time_t>(), 8);
+
+    let mut time_values: [libc::time_t; 2] = [123, 456];
+    let ptr = time_values.as_mut_ptr();
+
+    unsafe { libc::time(ptr) };
+
+    assert_ne!(time_values[0], 123);
+    assert_eq!(time_values[1], 456);
+}

src/windows/mod.rs

@@ -389,11 +389,36 @@ extern "C" {
     pub fn signal(signum: c_int, handler: sighandler_t) -> sighandler_t;
     pub fn raise(signum: c_int) -> c_int;
 
+    // By default, the following link to 64-bit variants where the expected
+    // `time_t` is also 64-bits.
+    //
+    // Under Windows x86 with GNU, `time_t` is still 32-bit wide on stable, so
+    // these routines have to link with their 32-bit variants.
+    //
+    // FIXME(#5062): once that PR gets merged, add `not(windows_gnu_time64)` to
+    // the below predicate, within the `all()` clause.
+    cfg_if! {
+        if #[cfg(all(target_arch = "x86", target_env = "gnu"))] {
+            #[link_name = "_ctime32"]
+            pub fn ctime(sourceTime: *const time_t) -> *mut c_char;
+            #[link_name = "_difftime32"]
+            pub fn difftime(timeEnd: time_t, timeStart: time_t) -> c_double;
+            #[link_name = "_gmtime32_s"]
+            pub fn gmtime_s(destTime: *mut tm, srcTime: *const time_t) -> c_int;
+            #[link_name = "_localtime32_s"]
+            pub fn localtime_s(tmDest: *mut tm, sourceTime: *const time_t) -> crate::errno_t;
+            #[link_name = "_time32"]
+            pub fn time(destTime: *mut time_t) -> time_t;
+        } else {
+            pub fn ctime(sourceTime: *const time_t) -> *mut c_char;
+            pub fn difftime(timeEnd: time_t, timeStart: time_t) -> c_double;
+            pub fn gmtime_s(destTime: *mut tm, srcTime: *const time_t) -> c_int;
+            pub fn localtime_s(tmDest: *mut tm, sourceTime: *const time_t) -> crate::errno_t;
+            pub fn time(destTime: *mut time_t) -> time_t;
+        }
+    }
+
     pub fn clock() -> clock_t;
-    pub fn ctime(sourceTime: *const time_t) -> *mut c_char;
-    pub fn difftime(timeEnd: time_t, timeStart: time_t) -> c_double;
-    #[link_name = "_gmtime64_s"]
-    pub fn gmtime_s(destTime: *mut tm, srcTime: *const time_t) -> c_int;
     #[link_name = "_get_daylight"]
     pub fn get_daylight(hours: *mut c_int) -> errno_t;
     #[link_name = "_get_dstbias"]
@@ -407,10 +432,6 @@ extern "C" {
         size_in_bytes: size_t,
         index: c_int,
     ) -> errno_t;
-    #[link_name = "_localtime64_s"]
-    pub fn localtime_s(tmDest: *mut tm, sourceTime: *const time_t) -> crate::errno_t;
-    #[link_name = "_time64"]
-    pub fn time(destTime: *mut time_t) -> time_t;
     #[link_name = "_tzset"]
     pub fn tzset();
     #[link_name = "_chmod"]