Crept in from my sandbox. Apologies
Derrick
On Aug 13, 2008, at 6:41 PM, Jeffrey Hutzelman <[EMAIL PROTECTED]> wrote:
--On Thursday, August 14, 2008 01:18:34 AM +0300 Dragos Tatulea <[EMAIL PROTECTED]
> wrote:
Hi,
I'm using the following config options: --enable-debug
--enable-debug-kernel --enable-warnings --enable-disconnected
--with-krb5-conf=/path and I'm getting the following compiling error:
vol-salvage.c:2692: error: lvalue required as left operand of
assignment
Looking into the code we find the line:
VNDISK_GET_LEN(vnodeLength, vnode);
Which expands into versions:
# define VNDISK_GET_LEN(N, V) FillInt64(N, (V)->reserved6, (V)-
>length)
(AFS_LARGEFILE_ENV enabled)
and FillInt64 is :
# define FillInt64(t,h,l) (t) = (h); ((afs_uint64)t) <<= 32; (t) |=
(l);
This was a bogus fix; applying a cast to the left-hand side of an
assignment is pretty much never the right thing to do (though it may
be appropriate to apply a cast to a pointer which is dereferenced to
produce the lhs). The result of a cast is not an lvalue.
Making FillInt64:
# define FillInt64(t,h,l) (t) = (h);t <<= 32; (t) |= (l);
Solves the problem... I know it's not the right way to go, but what
can I
make to have it compilable with gcc4.3?
This makes the error message go away, but that is not the same thing
as solving the problem. In fact, what this does is reintroduce the
bug that the previous change tried to fix.
The right fix is to rewrite the expression without using the <<=
shorthand, so that a cast can be applied to the _right-hand_
argument without trying to apply it to the left-hand side:
#define FillInt64(t,h,l) (t) = (h); (t) = ((afs_uint64)t) << 32; (t)
|=(l);
A simpler form would be:
#define FillInt64(t,h,l) (t) = ((afs_uint64)(h) << 32) | (l);
-- Jeff
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