uclibc: Replace linux_time_bits64 with a new uclibc32_time64 cfg

build.rs

@@ -54,6 +54,9 @@ enum Cfg {
     /// transition to 64-bit `time_t` and thus need `__*_time64` redirects. Implies `musl_v1_2`
     /// and 32-bit arch.
     MuslRedirTime64,
+    /// Corresponds to the `UCLIBC_USE_TIME64` config / `__UCLIBC_USE_TIME64__` define. Indicates
+    /// that `*time64` syscalls should be used. Implies 32-bit.
+    Uclibc32Time64,
 }
 
 const ALLOWED_CFGS: &[Cfg] = &[
@@ -76,6 +79,7 @@ const ALLOWED_CFGS: &[Cfg] = &[
     Cfg::MuslV1_2,
     Cfg::Musl32Time64,
     Cfg::MuslRedirTime64,
+    Cfg::Uclibc32Time64,
 ];
 
 impl fmt::Display for Cfg {
@@ -100,6 +104,7 @@ impl fmt::Display for Cfg {
             Cfg::MuslV1_2 => "musl_v1_2",
             Cfg::Musl32Time64 => "musl32_time64",
             Cfg::MuslRedirTime64 => "musl_redir_time64",
+            Cfg::Uclibc32Time64 => "uclibc32_time64",
         })
     }
 }
@@ -262,12 +267,6 @@ fn main() {
         }
     }
 
-    let uclibc_time64_env = env_flag("CARGO_CFG_LIBC_UNSTABLE_UCLIBC_TIME64");
-    let uclibc_time64 = target_env == "uclibc" && uclibc_time64_env;
-    if uclibc_time64 {
-        cfgs.push(Cfg::LinuxTimeBits64);
-    }
-
     let mut gnu_tb_env = env::var("CARGO_CFG_LIBC_UNSTABLE_GNU_TIME_BITS");
 
     // FIXME: remove these fallbacks in a few releases
@@ -314,6 +313,17 @@ fn main() {
         cfgs.push(Cfg::GnuTimeBits64);
     }
 
+    let uclibc_time64_env = env_flag("CARGO_CFG_LIBC_UNSTABLE_UCLIBC_TIME64");
+    let uclibc = target_env == "uclibc";
+    let uclibc32_time64 = uclibc && target_ptr_width == "32" && uclibc_time64_env;
+
+    if uclibc32_time64 {
+        if target_os == "linux" {
+            cfgs.push(Cfg::LinuxTimeBits64);
+        }
+        cfgs.push(Cfg::Uclibc32Time64);
+    }
+
     // On CI: deny all warnings
     if libc_ci {
         cfgs.push(Cfg::LibcDenyWarnings);
@@ -492,6 +502,16 @@ fn validate_cfg(list: &[Cfg], target_env: &str, target_os: &str, target_ptr_widt
                     "{cfg:?} set on non-musl1.2 platform"
                 )
             }
+            Cfg::Uclibc32Time64 => {
+                assert_eq!(target_env, "uclibc", "{cfg:?} set on non-gnu platform");
+                assert_eq!(target_ptr_width, "32", "{cfg:?} set on non-32-bit platform");
+                if target_os == "linux" {
+                    assert!(
+                        list.contains(&Cfg::LinuxTimeBits64),
+                        "missing 64-bit time_t Linux config"
+                    )
+                }
+            }
         }
     }
 }

ci/verify-build.py

@@ -420,6 +420,10 @@ def test_target(cfg: Cfg, target: Target) -> TargetResult:
         # Check with breaking changes from musl, including 64-bit time_t on 32-bit
         run(cmd, rustflags=f"{rustflags} --cfg=libc_unstable_musl_v1_2")
 
+    if "uclibc" in target_env:
+        # Equivalent of UCLIBC_USE_TIME64 on 32-bit targets, ignored on 64-bit
+        run(cmd, rustflags=f"{rustflags} --cfg=libc_unstable_uclibc_time64")
+
     # Test again without default features, i.e. without `std`
     run([*cmd, "--no-default-features"], rustflags=rustflags)
     run([*cmd, "--no-default-features", "--features=extra_traits"], rustflags=rustflags)

libc-test/build/main.rs

@@ -3995,10 +3995,14 @@ fn test_linux(t: &Target) {
         }
     }
 
-    let uclibc_use_time64 = env_flag("CARGO_CFG_LIBC_UNSTABLE_UCLIBC_TIME64");
-    if uclibc && uclibc_use_time64 {
+    let uclibc_time64_env = env_flag("CARGO_CFG_LIBC_UNSTABLE_UCLIBC_TIME64");
+    let uclibc32_time64 = uclibc && p32 && uclibc_time64_env;
+
+    if uclibc32_time64 {
         cfg.cfg("linux_time_bits64", None);
+        cfg.cfg("uclibc32_time64", None);
     }
+
     cfg.define("_GNU_SOURCE", None)
         // This macro re-defines fscanf,scanf,sscanf to link to the symbols that are
         // deprecated since glibc >= 2.29. This allows Rust binaries to link against

src/unix/linux_like/linux/uclibc/arm/mod.rs

@@ -220,13 +220,13 @@ s! {
         pub shm_perm: crate::ipc_perm,
         pub shm_segsz: size_t,
         pub shm_atime: crate::time_t,
-        #[cfg(not(linux_time_bits64))]
+        #[cfg(not(uclibc32_time64))]
         __unused1: Padding<c_ulong>,
         pub shm_dtime: crate::time_t,
-        #[cfg(not(linux_time_bits64))]
+        #[cfg(not(uclibc32_time64))]
         __unused2: Padding<c_ulong>,
         pub shm_ctime: crate::time_t,
-        #[cfg(not(linux_time_bits64))]
+        #[cfg(not(uclibc32_time64))]
         __unused3: Padding<c_ulong>,
         pub shm_cpid: crate::pid_t,
         pub shm_lpid: crate::pid_t,

src/unix/linux_like/linux/uclibc/mod.rs

@@ -14,7 +14,7 @@ pub type __priority_which_t = c_uint;
 
 cfg_if! {
     // Set `--cfg=libc_unstable_uclibc_time64` in RUSTFLAGS if your uClibc has 64-bit `time_t`.
-    if #[cfg(linux_time_bits64)] {
+    if #[cfg(uclibc32_time64)] {
         pub type time_t = i64;
         pub type suseconds_t = i64;
     } else {