Skip site navigation (1)Skip section navigation (2)
Date:      Tue, 25 Feb 2014 20:35:50 -0500
From:      Mark Johnston <markj@freebsd.org>
To:        Justin Hibbits <jhibbits@freebsd.org>
Cc:        svn-src-head@freebsd.org, svn-src-all@freebsd.org, src-committers <src-committers@freebsd.org>
Subject:   Re: svn commit: r262466 - head/sys/cddl/dev/systrace
Message-ID:  <20140226013550.GA16841@raichu>
In-Reply-To: <CAHSQbTCWRToOxwZOnCi-TzC_4vHUjppH5Kpdp238oL7HWNFc0A@mail.gmail.com>
References:  <201402250258.s1P2wCDd060659@svn.freebsd.org> <CAHSQbTCWRToOxwZOnCi-TzC_4vHUjppH5Kpdp238oL7HWNFc0A@mail.gmail.com>

next in thread | previous in thread | raw e-mail | index | archive | help
On Tue, Feb 25, 2014 at 03:17:56PM -0800, Justin Hibbits wrote:
> I think this broke powerpc building.  I see the following build failure:
> 
> cc1: warnings being treated as errors
> /home/chmeee/freebsd/head/sys/modules/dtrace/systrace/../../../cddl/dev/systrace/systrace.c:
> In function 'systrace_probe':
> /home/chmeee/freebsd/head/sys/modules/dtrace/systrace/../../../cddl/dev/systrace/systrace.c:218:
> warning: function called through a non-compatible type
> /home/chmeee/freebsd/head/sys/modules/dtrace/systrace/../../../cddl/dev/systrace/systrace.c:218:
> note: if this code is reached, the program will abort
> 

Hi Justin,

Sorry about this. I've reverted the commit.

I realize that the change introduced undefined behaviour, but a similar
trick is used elsewhere in the DTrace code to pass extra arguments at a
probe site. Calling dtrace_probe() through a function pointer (patch
below) makes the warning go away, but I don't really understand why.
clang doesn't emit warnings in either case.

Thanks,
-Mark

diff --git a/sys/cddl/dev/systrace/systrace.c b/sys/cddl/dev/systrace/systrace.c
index 83f0793..5f4b82f 100644
--- a/sys/cddl/dev/systrace/systrace.c
+++ b/sys/cddl/dev/systrace/systrace.c
@@ -168,8 +168,8 @@ static dtrace_pops_t systrace_pops = {
 static struct cdev		*systrace_cdev;
 static dtrace_provider_id_t	systrace_id;
 
-typedef void (*systrace_dtrace_probe)(dtrace_id_t, uintptr_t, uintptr_t,
-    uintptr_t, uintptr_t, uintptr_t, uintptr_t, uintptr_t, uintptr_t);
+typedef void (*systrace_probe_t)(dtrace_id_t, uintptr_t, uintptr_t, uintptr_t,
+    uintptr_t, uintptr_t, uintptr_t, uintptr_t, uintptr_t);
 
 #if !defined(LINUX_SYSTRACE)
 /*
@@ -214,8 +214,9 @@ systrace_probe(u_int32_t id, int sysnum, struct sysent *sysent, void *params,
 	}
 
 	/* Process the probe using the converted argments. */
-	((systrace_dtrace_probe)(dtrace_probe))(id, uargs[0], uargs[1],
-	    uargs[2], uargs[3], uargs[4], uargs[5], uargs[6], uargs[7]);
+	systrace_probe_t probe = (systrace_probe_t)dtrace_probe;
+	probe(id, uargs[0], uargs[1], uargs[2], uargs[3], uargs[4],
+	    uargs[5], uargs[6], uargs[7]);
 }
 
 #endif



Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?20140226013550.GA16841>