syscall_to_function.h: simplify, and avoid C++20 extension

The macros in syscall_to_function.h used "__VA_OPT__", which is a C++20
extension that older compilers (such as on Ubuntu 18.04) don't understand.

Luckily, we don't even need to use this extension. The macros in this file
used an elaborate way to change __OSV_TO_FUNCTION_SYS_fcntl to just "fcntl"
with all the parameters intact. But the easiest way to achieve that goal
is just to #define the name - without even telling the C preprocessor that
this is a function! It will just change "__OSV_TO_FUNCTION_SYS_fcntl" to
"fcntl" and not worry at all about anything which may or may not appear
afterwards in parentheses. It's easier, shorter, and not C++20-specific.

Fixes #1099

Signed-off-by: Nadav Har'El <[email protected]>

libc/syscall_to_function.h

@@ -2,33 +2,21 @@
 #include <unistd.h>
 #include <errno.h>
 
-#define sys_open(filename, flags, ...) (open(filename, flags __VA_OPT__(,) __VA_ARGS__))
-
-#define __OSV_TO_FUNCTION_SYS_open(filename, flags, ...) (open(filename, flags __VA_OPT__(,) __VA_ARGS__))
-
-#define __OSV_TO_FUNCTION_SYS_close(fd) (close(fd))
-
-#define __OSV_TO_FUNCTION_SYS_lseek(file, off, whence) (lseek(file, off, whence))
-
-#define __OSV_TO_FUNCTION_SYS_fcntl(fd, cmd, ...) (fcntl(fd, cmd __VA_OPT__(,) __VA_ARGS__))
-
-#define __OSV_TO_FUNCTION_SYS_clock_gettime(c, t, x) (clock_gettime(c, t))
-
-#define __OSV_TO_FUNCTION_SYS_access(p, i) (access(p, i))
-
-#define __OSV_TO_FUNCTION_SYS_ioctl(fd, cmd, args) (ioctl(fd, cmd, args))
-
-#define __OSV_TO_FUNCTION_SYS_fstat(fd, st) (fstat(fd, st))
-
-#define __OSV_TO_FUNCTION_SYS_lstat(fd, st) (lstat(fd, st))
-
-#define __OSV_TO_FUNCTION_SYS_unlink(path) (unlink(path))
-
-#define __OSV_TO_FUNCTION_SYS_rmdir(path) (rmdir(path))
-
-#define __OSV_TO_FUNCTION_SYS_readv(fd, cmd, args) (readv(fd, cmd, args))
-
-#define __OSV_TO_FUNCTION_SYS_writev(fd, cmd, args) (writev(fd, cmd, args))
+#define sys_open open
+
+#define __OSV_TO_FUNCTION_SYS_open          open
+#define __OSV_TO_FUNCTION_SYS_close         close
+#define __OSV_TO_FUNCTION_SYS_lseek         lseek
+#define __OSV_TO_FUNCTION_SYS_fcntl         fcntl
+#define __OSV_TO_FUNCTION_SYS_clock_gettime clock_gettime
+#define __OSV_TO_FUNCTION_SYS_access        access
+#define __OSV_TO_FUNCTION_SYS_ioctl         ioctl
+#define __OSV_TO_FUNCTION_SYS_fstat         fstat
+#define __OSV_TO_FUNCTION_SYS_lstat         lstat
+#define __OSV_TO_FUNCTION_SYS_unlink        unlink
+#define __OSV_TO_FUNCTION_SYS_rmdir         rmdir
+#define __OSV_TO_FUNCTION_SYS_readv         readv
+#define __OSV_TO_FUNCTION_SYS_writev        writev
 
 #undef __syscall
 #define __syscall(sys_number, ...) (__OSV_TO_FUNCTION_##sys_number(__VA_ARGS__) < 0 ? -errno : 0)