Date: Mon, 22 Mar 2004 19:36:28 -0800
From: Paul Jackson <pj@sgi.com>
To: William Lee Irwin III <wli@holomorphy.com>
Cc: colpatch@us.ibm.com, linux-kernel@vger.kernel.org, mbligh@aracnet.com,
       akpm@osdl.org, haveblue@us.ibm.com, hch@infradead.org
Subject: Re: [PATCH] Introduce nodemask_t ADT [0/7]
Message-Id: <20040322193628.4278db8c.pj@sgi.com>
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> gcc flat out miscompiled such inlines last I checked (Zwane shipped the
> bugreport IIRC).

The one error I've heard tell of recently is one that Andi Kleen hit in
include/linux/bitmap.h.  He had to compute the copy length explicitly in
a separate variable, or gcc forgot to do it (I forget the details).  The
change is:


 static inline void bitmap_copy(unsigned long *dst,
                        const unsigned long *src, int bits)
 {
-       memcpy(dst, src, BITS_TO_LONGS(bits)*sizeof(unsigned long));
+       int len = BITS_TO_LONGS(bits)*sizeof(unsigned long);
+       memcpy(dst, src, len);
 }


Do you have any more pointers/info on the miscompile you quote above?
Like - how long ago - what gcc version ...

It would be an insult to wrap the entire cpumask design around the
axle of such non-specific allegations of gcc misconduct.  Better to
get the API right, and then deal with specific tool bugs as necessary.

Or, as Linus might say (did say, in a quite different context):

  Never _ever_ make your source-code look worse because your tools suck. Fix
  the tools instead.

-- 
                          I won't rest till it's the best ...
                          Programmer, Linux Scalability
                          Paul Jackson <pj@sgi.com> 1.650.933.1373
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