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Re: [PATCH 2/3] Simplify and inline get_uleb128 and get_sleb128
- From: Petr Machata <pmachata at redhat dot com>
- To: elfutils-devel at lists dot fedorahosted dot org
- Date: Wed, 23 Apr 2014 20:32:30 +0200
- Subject: Re: [PATCH 2/3] Simplify and inline get_uleb128 and get_sleb128
Richard Henderson <firstname.lastname@example.org> writes:
> On 04/23/2014 03:17 AM, Petr Machata wrote:
>> Wouldn't something like this get us off the hook as well?
>> - (var) |= (typeof (var)) __s.i << ((nth) * 7); \
>> + (var) |= (typeof (var)) \
>> + (((uint64_t) (typeof (var)) __s.i) << ((nth) * 7)); \
>> We are really only using the bitfield trick to avoid having to
>> sign-extend by hand, but we can shift unsigned without losing anything.
> It gets us off the hook, but might introduce a 64-bit shift where
> only a 32-bit shift was required.
Good point, but get_sleb128_step is only used from __libdw_get_sleb128,
where the type is int64_t. This macro is not safe for outside use
anyway, as it uses its parameters more than once.
Hmm, should we maybe #undef it after __libdw_get_sleb128, so that it's
clear that it's for local use only?