platform: nsync futex: fix build on riscv32

[clementperon]

RISCV glibc has decided to use 64bit time_t from get go unlike other 32bit architecture therefore aliasing __NR_futex to __NR_futex_time64 helps avoid the below errors on rv32

error: '__NR_futex' was not declared in this scope
| 21 | return (syscall (__NR_futex, uaddr, op, val, timeout, uaddr2, val3));
| |

Issue linked to NobuoTsukamoto/meta-onnxruntime#3

@m3bm3b

[m3bm3b]

Hi, thanks for the change.

Two things:

• If we're going to fix things for 64-bit time_t on Linux on 32-bit architectures, it might be good to do it also for builds that can use 64-bit time when _TIME_BITS==64.
• After a few changes involving executable statements inside #if/#endif blocks, code can become unreadable, and test coverage less obvious.

Does the following change work for you? If so, could you use that instead?
I have tried it on x86_64, and on x86_32 with _TIME_BITS==64 and without.

diff --git a/platform/linux/src/nsync_semaphore_futex.c b/platform/linux/src/nsync_semaphore_futex.c
index f54d1c8..b34d1a1 100644
--- a/platform/linux/src/nsync_semaphore_futex.c
+++ b/platform/linux/src/nsync_semaphore_futex.c
@@ -16,9 +16,19 @@

NSYNC_CPP_START_

+/* Linux uses 64-bit time when _TIME_BITS==64; only __NR_futex_time64 is

• defined for some CPU types. */
  +#define NSYNC_NR_FUTEX __NR_futex
  +#if defined(__NR_futex_time64) && (defined(_TIME_BITS) || !defined(__NR_futex))
  +#if _TIME_BITS == 64 || !defined(__NR_futex)
  +#undef NSYNC_NR_FUTEX
  +#define NSYNC_NR_FUTEX __NR_futex_time64
  +#endif
  +#endif

static int futex (int *uaddr, int op, int val, const struct timespec *timeout, int *uaddr2,
int val3) {

•   return (syscall (__NR_futex, uaddr, op, val, timeout, uaddr2, val3));
  

•   return (syscall (NSYNC_NR_FUTEX, uaddr, op, val, timeout, uaddr2, val3));
  

}

/* Check that atomic operations on nsync_atomic_uint32_ can be applied to int. */

[m3bm3b]

Github's text processing mangled my proposed change. Here's another try:

diff --git a/platform/linux/src/nsync_semaphore_futex.c b/platform/linux/src/nsync_semaphore_futex.c
index f54d1c8..b34d1a1 100644
--- a/platform/linux/src/nsync_semaphore_futex.c
+++ b/platform/linux/src/nsync_semaphore_futex.c
@@ -16,9 +16,19 @@
 
 NSYNC_CPP_START_
 
+/* Linux uses 64-bit time when _TIME_BITS==64; only __NR_futex_time64 is
+   defined for some CPU types. */
+#define NSYNC_NR_FUTEX __NR_futex
+#if defined(__NR_futex_time64) && (defined(_TIME_BITS) || !defined(__NR_futex))
+#if _TIME_BITS == 64 || !defined(__NR_futex)
+#undef NSYNC_NR_FUTEX
+#define NSYNC_NR_FUTEX __NR_futex_time64
+#endif
+#endif
+
 static int futex (int *uaddr, int op, int val, const struct timespec *timeout, int *uaddr2,
                  int val3) {
-       return (syscall (__NR_futex, uaddr, op, val, timeout, uaddr2, val3));
+       return (syscall (NSYNC_NR_FUTEX, uaddr, op, val, timeout, uaddr2, val3));
 }
 
 /* Check that atomic operations on nsync_atomic_uint32_ can be applied to int. */

[m3bm3b]

Somehow you deleted the semicolon on the return statement (line 31).

Could you add it and perhaps confirm that the code does in fact compile for 32-bit RISC-V Linux?

Thanks.

[clementperon]

@m3bm3b yes I was trying to build, I will come back as soon as its working

[m3bm3b]

I managed to test the commit (with the semicolon added) under user-mode qemu-riscv32,
using a riscv32 gcc cross-compiler toolchain.
I also verified that that without the commit, the RISCV32 build fails in the way we expect.

(I tried to boot Linux using qemu-system-riscv32, but there seem to be many rough edges
in the instructions I could find, so I contented myself with user-mode qemu.)

[m3bm3b]

Looks good. Thanks.