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>

1 files changed, 3 insertions, 2 deletions

diff --git a/htl/cthreads-compat.c b/htl/cthreads-compat.c
index 55043a8bb4..2a0a95b6ff 100644
--- a/htl/cthreads-compat.c
+++ b/htl/cthreads-compat.c
@@ -25,8 +25,9 @@ void
 __cthread_detach (__cthread_t thread)
 {
   int err;
+  pthread_t pthread = (pthread_t) (uintptr_t) thread;
 
-  err = __pthread_detach ((pthread_t) thread);
+  err = __pthread_detach (pthread);
   assert_perror (err);
 }
 weak_alias (__cthread_detach, cthread_detach)
@@ -40,7 +41,7 @@ __cthread_fork (__cthread_fn_t func, void *arg)
   err = __pthread_create (&thread, NULL, func, arg);
   assert_perror (err);
 
-  return (__cthread_t) thread;
+  return (__cthread_t) (uintptr_t) thread;
 }
 weak_alias (__cthread_fork, cthread_fork)