- localtime_r: Ensure string deduplication with a single buffer allocation

    - tests: Add additional scenarios for libc::localtime_r validation

Signed-off-by: shamb0 <[email protected]>

Author: shamb0

src/shims/time.rs

@@ -1,10 +1,13 @@
 use std::ffi::{OsStr, OsString};
 use std::fmt::Write;
 use std::str::FromStr;
+use std::sync::OnceLock;
 use std::time::{Duration, SystemTime};
 
 use chrono::{DateTime, Datelike, Offset, Timelike, Utc};
 use chrono_tz::Tz;
+use rustc_middle::ty::Ty;
+use rustc_middle::ty::layout::LayoutOf;
 
 use crate::*;
 
@@ -180,6 +183,9 @@ pub trait EvalContextExt<'tcx>: crate::MiriInterpCxExt<'tcx> {
         if !matches!(&*this.tcx.sess.target.os, "solaris" | "illumos") {
             // tm_zone represents the timezone value in the form of: +0730, +08, -0730 or -08.
             // This may not be consistent with libc::localtime_r's result.
+            const TZ_MAX_LEN: u64 = 6; // 5 chars max + null terminator
+            static TIMEZONE_PTR: OnceLock<Pointer> = OnceLock::new();
+
             let offset_in_seconds = dt.offset().fix().local_minus_utc();
             let tm_gmtoff = offset_in_seconds;
             let mut tm_zone = String::new();
@@ -195,12 +201,23 @@ pub trait EvalContextExt<'tcx>: crate::MiriInterpCxExt<'tcx> {
                 write!(tm_zone, "{:02}", offset_min).unwrap();
             }
 
-            // FIXME: String de-duplication is needed so that we only allocate this string only once
-            // even when there are multiple calls to this function.
-            let tm_zone_ptr = this
-                .alloc_os_str_as_c_str(&OsString::from(tm_zone), MiriMemoryKind::Machine.into())?;
-
-            this.write_pointer(tm_zone_ptr, &this.project_field_named(&result, "tm_zone")?)?;
+            // Ensure string deduplication by allocating the buffer only once,
+            // even if the function is called multiple times.
+            let tm_zone_ptr = TIMEZONE_PTR.get_or_init(|| {
+                let arg_type = Ty::new_array(this.tcx.tcx, this.tcx.types.u8, TZ_MAX_LEN);
+                let arg_place = this
+                    .allocate(this.layout_of(arg_type).unwrap(), MiriMemoryKind::Machine.into())
+                    .expect("timezone buffer allocation failed");
+                arg_place.ptr()
+            });
+
+            // Write the `tm_zone` string into the allocated buffer.
+            let (written, _) =
+                this.write_os_str_to_c_str(&OsString::from(tm_zone), *tm_zone_ptr, TZ_MAX_LEN)?;
+            assert!(written);
+
+            // Write the timezone pointer and offset into the result structure.
+            this.write_pointer(*tm_zone_ptr, &this.project_field_named(&result, "tm_zone")?)?;
             this.write_int_fields_named(&[("tm_gmtoff", tm_gmtoff.into())], &result)?;
         }
         interp_ok(result.ptr())

tests/pass-dep/libc/libc-time.rs

@@ -5,7 +5,10 @@ use std::{env, mem, ptr};
 fn main() {
     test_clocks();
     test_posix_gettimeofday();
-    test_localtime_r();
+    test_localtime_r_gmt();
+    test_localtime_r_pst();
+    test_localtime_r_epoch();
+    test_localtime_r_future();
 }
 
 /// Tests whether clock support exists at all
@@ -46,14 +49,9 @@ fn test_posix_gettimeofday() {
     assert_eq!(is_error, -1);
 }
 
-fn test_localtime_r() {
-    // Set timezone to GMT.
-    let key = "TZ";
-    env::set_var(key, "GMT");
-
-    const TIME_SINCE_EPOCH: libc::time_t = 1712475836;
-    let custom_time_ptr = &TIME_SINCE_EPOCH;
-    let mut tm = libc::tm {
+// Helper function to create an empty tm struct
+fn create_empty_tm() -> libc::tm {
+    libc::tm {
         tm_sec: 0,
         tm_min: 0,
         tm_hour: 0,
@@ -77,7 +75,17 @@ fn test_localtime_r() {
             target_os = "android"
         ))]
         tm_zone: std::ptr::null_mut::<libc::c_char>(),
-    };
+    }
+}
+
+// Original GMT test
+fn test_localtime_r_gmt() {
+    // Set timezone to GMT.
+    let key = "TZ";
+    env::set_var(key, "GMT");
+    const TIME_SINCE_EPOCH: libc::time_t = 1712475836; // 2024-04-07 07:43:56 GMT
+    let custom_time_ptr = &TIME_SINCE_EPOCH;
+    let mut tm = create_empty_tm();
     let res = unsafe { libc::localtime_r(custom_time_ptr, &mut tm) };
 
     assert_eq!(tm.tm_sec, 56);
@@ -95,20 +103,127 @@ fn test_localtime_r() {
         target_os = "freebsd",
         target_os = "android"
     ))]
-    assert_eq!(tm.tm_gmtoff, 0);
+    {
+        assert_eq!(tm.tm_gmtoff, 0);
+        unsafe {
+            assert_eq!(std::ffi::CStr::from_ptr(tm.tm_zone).to_str().unwrap(), "+00");
+        }
+    }
+
+    // The returned value is the pointer passed in.
+    assert!(ptr::eq(res, &mut tm));
+
+    // Remove timezone setting.
+    env::remove_var(key);
+}
+
+// PST timezone test (testing different timezone handling)
+fn test_localtime_r_pst() {
+    let key = "TZ";
+    env::set_var(key, "PST8PDT");
+    const TIME_SINCE_EPOCH: libc::time_t = 1712475836;
+    let custom_time_ptr = &TIME_SINCE_EPOCH;
+    let mut tm = create_empty_tm();
+
+    let res = unsafe { libc::localtime_r(custom_time_ptr, &mut tm) };
+
+    assert_eq!(tm.tm_sec, 56);
+    assert_eq!(tm.tm_min, 43);
+    assert_eq!(tm.tm_hour, 0); // 7 - 7 = 0 (PDT offset)
+    assert_eq!(tm.tm_mday, 7);
+    assert_eq!(tm.tm_mon, 3);
+    assert_eq!(tm.tm_year, 124);
+    assert_eq!(tm.tm_wday, 0);
+    assert_eq!(tm.tm_yday, 97);
+    assert_eq!(tm.tm_isdst, -1); // DST information unavailable
+
     #[cfg(any(
         target_os = "linux",
         target_os = "macos",
         target_os = "freebsd",
         target_os = "android"
     ))]
-    unsafe {
-        assert_eq!(std::ffi::CStr::from_ptr(tm.tm_zone).to_str().unwrap(), "+00")
-    };
+    {
+        assert_eq!(tm.tm_gmtoff, -25200); // -7 hours in seconds
+        unsafe {
+            assert_eq!(std::ffi::CStr::from_ptr(tm.tm_zone).to_str().unwrap(), "-07");
+        }
+    }
+
+    assert!(ptr::eq(res, &mut tm));
+    env::remove_var(key);
+}
+
+// Unix epoch test (edge case testing)
+fn test_localtime_r_epoch() {
+    let key = "TZ";
+    env::set_var(key, "GMT");
+    const TIME_SINCE_EPOCH: libc::time_t = 0; // 1970-01-01 00:00:00
+    let custom_time_ptr = &TIME_SINCE_EPOCH;
+    let mut tm = create_empty_tm();
+
+    let res = unsafe { libc::localtime_r(custom_time_ptr, &mut tm) };
+
+    assert_eq!(tm.tm_sec, 0);
+    assert_eq!(tm.tm_min, 0);
+    assert_eq!(tm.tm_hour, 0);
+    assert_eq!(tm.tm_mday, 1);
+    assert_eq!(tm.tm_mon, 0);
+    assert_eq!(tm.tm_year, 70);
+    assert_eq!(tm.tm_wday, 4); // Thursday
+    assert_eq!(tm.tm_yday, 0);
+    assert_eq!(tm.tm_isdst, -1);
+
+    #[cfg(any(
+        target_os = "linux",
+        target_os = "macos",
+        target_os = "freebsd",
+        target_os = "android"
+    ))]
+    {
+        assert_eq!(tm.tm_gmtoff, 0);
+        unsafe {
+            assert_eq!(std::ffi::CStr::from_ptr(tm.tm_zone).to_str().unwrap(), "+00");
+        }
+    }
 
-    // The returned value is the pointer passed in.
     assert!(ptr::eq(res, &mut tm));
+    env::remove_var(key);
+}
 
-    // Remove timezone setting.
+// Future date test (testing large values)
+fn test_localtime_r_future() {
+    let key = "TZ";
+    env::set_var(key, "GMT");
+    const TIME_SINCE_EPOCH: libc::time_t = 2524608000; // 2050-01-01 00:00:00
+    let custom_time_ptr = &TIME_SINCE_EPOCH;
+    let mut tm = create_empty_tm();
+
+    let res = unsafe { libc::localtime_r(custom_time_ptr, &mut tm) };
+
+    assert_eq!(tm.tm_sec, 0);
+    assert_eq!(tm.tm_min, 0);
+    assert_eq!(tm.tm_hour, 0);
+    assert_eq!(tm.tm_mday, 1);
+    assert_eq!(tm.tm_mon, 0);
+    assert_eq!(tm.tm_year, 150);
+    assert_eq!(tm.tm_wday, 6); // Saturday
+    assert_eq!(tm.tm_yday, 0);
+    assert_eq!(tm.tm_isdst, -1);
+
+    #[cfg(any(
+        target_os = "linux",
+        target_os = "macos",
+        target_os = "freebsd",
+        target_os = "android"
+    ))]
+    {
+        assert_eq!(tm.tm_gmtoff, 0);
+        unsafe {
+            assert_eq!(std::ffi::CStr::from_ptr(tm.tm_zone).to_str().unwrap(), "+00");
+        }
+    }
+
+    assert!(ptr::eq(res, &mut tm));
     env::remove_var(key);
 }