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>
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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
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