[PATCH v3] Suppress -Wcast-qual warnings in bsearch

[Jonathan Wakely <jwakely@redhat.com>]

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On 19/05/21 16:50 +0100, Jonathan Wakely wrote:
>On 19/05/21 15:37 +0000, Joseph Myers wrote:
>>On Wed, 19 May 2021, Jonathan Wakely via Libc-alpha wrote:
>>
>>>+#pragma GCC diagnostic push
>>>+#pragma GCC diagnostic ignored "-Wcast-qual"
>>> 	return (void *) __p;
>>>+#pragma GCC diagnostic pop
>>
>>I think such pragma uses in installed headers should be conditional on
>>__GNUC_PREREQ (4, 6) (either directly or via conditionally defining a
>>macro in sys/cdefs.h).
>
>Good point.
>
>I spent about two minutes trying to do something with _Pragma in
>sys/cdefs.h to allow:
>
>__GLIBC_IGNORE_WARNING("-Wcast-qual")
>  return (void *) __p;
>__GLIBC_UNIGNORE_WARNING
>
>but didn't get it working, so here's a patch that just tests
>__GNUC_PREREQ directly.

Resending patch v2 with a modified subject, to see if patchwork picks
it up.



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commit ee7c2451a102b4cd3c87a31b3156ad4458729840
Author: Jonathan Wakely <jwakely@redhat.com>
Date:   Wed May 19 16:48:19 2021 +0100

    Suppress -Wcast-qual warnings in bsearch
    
    The first cast to (void *) is redundant but should be (const void *)
    anyway, because that's the type of the lvalue being assigned to.
    
    The second cast is necessary and intentionally not const-correct, so
    tell the compiler not to warn about it.

diff --git a/bits/stdlib-bsearch.h b/bits/stdlib-bsearch.h
index 4132dc6af0..d688ed2e15 100644
--- a/bits/stdlib-bsearch.h
+++ b/bits/stdlib-bsearch.h
@@ -29,14 +29,21 @@ bsearch (const void *__key, const void *__base, size_t __nmemb, size_t __size,
   while (__l < __u)
     {
       __idx = (__l + __u) / 2;
-      __p = (void *) (((const char *) __base) + (__idx * __size));
+      __p = (const void *) (((const char *) __base) + (__idx * __size));
       __comparison = (*__compar) (__key, __p);
       if (__comparison < 0)
 	__u = __idx;
       else if (__comparison > 0)
 	__l = __idx + 1;
       else
+#if __GNUC_PREREQ(4, 6)
+# pragma GCC diagnostic push
+# pragma GCC diagnostic ignored "-Wcast-qual"
+#endif
 	return (void *) __p;
+#if __GNUC_PREREQ(4, 6)
+# pragma GCC diagnostic pop
+#endif
     }
 
   return NULL;