mach, hurd: Cast through uintptr_t

When casting between a pointer and an integer of a different size, GCC
emits a warning (which is escalated to a build failure by -Werror).
Indeed, if what you start with is a pointer, which you then cast to a
shorter integer and then back again, you're going to cut off some bits
of the pointer.

But if you start with an integer (such as mach_port_t), then cast it to
a longer pointer (void *), and then back to a shorter integer, you are
fine. To keep GCC happy, cast through an intermediary uintptr_t, which
is always the same size as a pointer.

Signed-off-by: Sergey Bugaev <bugaevc@gmail.com>
Message-Id: <20230212111044.610942-4-bugaevc@gmail.com>

4 files changed, 17 insertions, 9 deletions

diff --git a/hurd/fopenport.c b/hurd/fopenport.c
index 60afb44552..be6aa30c7e 100644
--- a/hurd/fopenport.c
+++ b/hurd/fopenport.c
@@ -28,9 +28,10 @@ readio (void *cookie, char *buf, size_t n)
   mach_msg_type_number_t nread;
   error_t err;
   char *bufp = buf;
+  io_t io = (io_t) (uintptr_t) cookie;
 
   nread = n;
-  if (err = __io_read ((io_t) cookie, &bufp, &nread, -1, n))
+  if (err = __io_read (io, &bufp, &nread, -1, n))
     return __hurd_fail (err);
 
   if (bufp != buf)
@@ -50,8 +51,9 @@ writeio (void *cookie, const char *buf, size_t n)
 {
   vm_size_t wrote;
   error_t err;
+  io_t io = (io_t) (uintptr_t) cookie;
 
-  if (err = __io_write ((io_t) cookie, buf, n, -1, &wrote))
+  if (err = __io_write (io, buf, n, -1, &wrote))
     return __hurd_fail (err);
 
   return wrote;
@@ -65,7 +67,8 @@ seekio (void *cookie,
 	off64_t *pos,
 	int whence)
 {
-  error_t err = __io_seek ((file_t) cookie, *pos, whence, pos);
+  io_t io = (io_t) (uintptr_t) cookie;
+  error_t err = __io_seek (io, *pos, whence, pos);
   return err ? __hurd_fail (err) : 0;
 }
 
@@ -74,8 +77,9 @@ seekio (void *cookie,
 static int
 closeio (void *cookie)
 {
+  io_t io = (io_t) (uintptr_t) cookie;
   error_t error = __mach_port_deallocate (__mach_task_self (),
-					  (mach_port_t) cookie);
+					  io);
   if (error)
     return __hurd_fail (error);
   return 0;
@@ -127,6 +131,7 @@ __fopenport (mach_port_t port, const char *mode)
       return NULL;
     }
 
-  return fopencookie ((void *) port, mode, funcsio);
+  return fopencookie ((void *) (uintptr_t) port,
+                      mode, funcsio);
 }
 weak_alias (__fopenport, fopenport)
diff --git a/hurd/hurd/port.h b/hurd/hurd/port.h
index fdba8db5ed..1e473978d8 100644
--- a/hurd/hurd/port.h
+++ b/hurd/hurd/port.h
@@ -96,7 +96,7 @@ _hurd_port_locked_get (struct hurd_port *port,
   if (result != MACH_PORT_NULL)
     {
       link->cleanup = &_hurd_port_cleanup;
-      link->cleanup_data = (void *) result;
+      link->cleanup_data = (void *) (uintptr_t) result;
       _hurd_userlink_link (&port->users, link);
     }
   __spin_unlock (&port->lock);
diff --git a/hurd/port-cleanup.c b/hurd/port-cleanup.c
index 08ab3d47cb..ad43b83013 100644
--- a/hurd/port-cleanup.c
+++ b/hurd/port-cleanup.c
@@ -26,7 +26,8 @@
 void
 _hurd_port_cleanup (void *cleanup_data, jmp_buf env, int val)
 {
-  __mach_port_deallocate (__mach_task_self (), (mach_port_t) cleanup_data);
+  mach_port_t port = (mach_port_t) (uintptr_t) cleanup_data;
+  __mach_port_deallocate (__mach_task_self (), port);
 }
 
 /* We were cancelled while using a port, and called from the cleanup unwinding.
diff --git a/hurd/vpprintf.c b/hurd/vpprintf.c
index fe73494684..010f04ca2c 100644
--- a/hurd/vpprintf.c
+++ b/hurd/vpprintf.c
@@ -25,8 +25,9 @@
 static ssize_t
 do_write (void *cookie,	const char *buf, size_t n)
 {
+  io_t io = (io_t) (uintptr_t) cookie;
   vm_size_t amount = n;
-  error_t error = __io_write ((io_t) cookie, buf, n, -1, &amount);
+  error_t error = __io_write (io, buf, n, -1, &amount);
   if (error)
     return __hurd_fail (error);
   return n;
@@ -51,7 +52,8 @@ vpprintf (io_t port, const char *format, va_list arg)
 #endif
 
   _IO_cookie_init (&temp_f.cfile, _IO_NO_READS,
-		   (void *) port, (cookie_io_functions_t) { write: do_write });
+                   (void *) (uintptr_t) port,
+                   (cookie_io_functions_t) { write: do_write });
 
   done = __vfprintf_internal (&temp_f.cfile.__fp.file, format, arg, 0);