trivial packing for on-stack structs

* io.c (struct io_advise_struct): 32 => 24 bytes on 64-bit
* io.c (struct io_internal_writev_struct): 24 => 16 bytes on 64-bit
* process.c (struct waitpid_arg): ditto

Slightly reduce stack pressure.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@47594 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

ChangeLog

@@ -1,3 +1,9 @@
+Mon Sep 15 16:21:10 2014  Eric Wong  <e@80x24.org>
+
+	* io.c (struct io_advise_struct): 32 => 24 bytes on 64-bit
+	* io.c (struct io_internal_writev_struct): 24 => 16 bytes on 64-bit
+	* process.c (struct waitpid_arg): ditto
+
 Mon Sep 15 10:29:25 2014  Natalie Weizenbaum  <nweiz@google.com>
 
 	* ext/pathname/lib/pathname.rb (SAME_PATHS):

io.c

@@ -941,8 +941,8 @@ struct io_internal_write_struct {
 #ifdef HAVE_WRITEV
 struct io_internal_writev_struct {
     int fd;
-    const struct iovec *iov;
     int iovcnt;
+    const struct iovec *iov;
 };
 #endif
 
@@ -8462,9 +8462,9 @@ static VALUE sym_normal,   sym_sequential, sym_random,
 #ifdef HAVE_POSIX_FADVISE
 struct io_advise_struct {
     int fd;
+    int advice;
     off_t offset;
     off_t len;
-    int advice;
 };
 
 static VALUE

process.c

@@ -740,8 +740,8 @@ waitall_each(rb_pid_t pid, int status, VALUE ary)
 #else
 struct waitpid_arg {
     rb_pid_t pid;
-    int *st;
     int flags;
+    int *st;
 };
 #endif