Fix usage with musl libc.

linux_syscall_support.h

Index: linux_syscall_support.h
diff --git a/linux_syscall_support.h b/linux_syscall_support.h
index 8a42c1c8687b2af252811c28581cabfd89a3a3ae..34339f81373a026b3a22ec64655ef0e192ce7471 100644
--- a/linux_syscall_support.h
+++ b/linux_syscall_support.h
@@ -100,6 +100,9 @@ extern "C" {
 #endif
 
 #include <errno.h>
+#ifndef _GNU_SOURCE
+#define _GNU_SOURCE /* musl libc defines loff_t only with _GNU_SOURC */

[Mark Seaborn, 2016/03/13 19:59:49]

Typo: "SOURC"

I'm not sure that defining _GNU_SOURCE here is a good idea, because:
 * it will leak to files #included after linux_syscall_support.h
 * it won't work if fcntl.h was #included earlier

What's your use case?  i.e. What are you building that uses
linux_syscall_support.h?

+#endif
 #include <fcntl.h>
 #include <sched.h>
 #include <signal.h>
@@ -1055,6 +1058,12 @@ struct kernel_statfs {
 #ifndef __NR_pwrite64
 #define __NR_pwrite64            18
 #endif
+#ifndef __NR_pread
+#define __NR_pread __NR_pread64

[Mark Seaborn, 2016/03/13 19:59:49]

Please explain what this fixes.  What's your test case?

+#endif
+#ifndef __NR_pwrite
+#define __NR_pwrite __NR_pwrite64
+#endif
 #ifndef __NR_setresuid
 #define __NR_setresuid          117
 #define __NR_getresuid          118