[vlc-commits] [Git][videolan/vlc][master] linux: use futex_time64 where applicable

[Rémi Denis-Courmont (@Courmisch)]

Rémi Denis-Courmont pushed to branch master at VideoLAN / VLC


Commits:
949fb1d0 by Rémi Denis-Courmont at 2022-01-29T16:26:15+00:00
linux: use futex_time64 where applicable

This adds support for 32-bit RISC-V, which only supports 64-bit time_t,
and thus lacks a plain futex system call. This also adds (future)
support for building with a 64-bit time_t ABI on a 32-bit platform.

- - - - -


1 changed file:

- src/linux/thread.c


Changes:

=====================================
src/linux/thread.c
=====================================
@@ -53,7 +53,27 @@ unsigned long vlc_thread_id(void)
 static int sys_futex(void *addr, int op, unsigned val,
                      const struct timespec *to, void *addr2, int val3)
 {
-    return syscall(__NR_futex, addr, op, val, to, addr2, val3);
+    /* The futex Linux kernel system call exists in two variants:
+     * - the original one for use with long time_t, which suffers from the
+     *   year 2038 problem on 32-bit architectures,
+     * - the "time64" one for use with 64-bit time_t, which lacks backward
+     *   binary compatibility with 32-bit long time_t on 32-bit architectures.
+     */
+    static_assert (sizeof (time_t) == sizeof (long) || sizeof (time_t) == 8,
+                   "Unrecognised time_t type definition");
+
+#if !defined (__NR_futex)
+    /* Recent 32-bit platforms (e.g. riscv32) only support 64-bit time_t. */
+    static_assert (sizeof (time_t) == 8, "Expected 64-bit time_t");
+    const long num = __NR_futex_time64;
+#elif !defined (__NR_futex_time64)
+    static_assert (sizeof (time_t) == sizeof (long), "Expected long time_t");
+    const long num = __NR_futex;
+#else
+    const long num = sizeof (time_t) == sizeof (long)
+                     ? __NR_futex : __NR_futex_time64;
+#endif
+    return syscall(num, addr, op, val, to, addr2, val3);
 }
 
 static int vlc_futex_wake(void *addr, int nr)



View it on GitLab: https://code.videolan.org/videolan/vlc/-/commit/949fb1d03d57d18009e20bb821f9d3e70db17ab8

-- 
View it on GitLab: https://code.videolan.org/videolan/vlc/-/commit/949fb1d03d57d18009e20bb821f9d3e70db17ab8
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