[Spirit] [bind] Compiler warning dependent on number of rules?

[Norbert Wenzel-2]

Hello,

I'm currently parsing some data using Spirit together with boost::bind
to set the callbacks for Spirit. In release build I get a compiler (gcc
4.4.1) warning from bind:
warning: dereferencing pointer ‘val’ does break strict-aliasing rules

I was able to find the lines causing this problem by commenting them
out, rebuilding and the error got away. The strange thing is, that when
I copy some other parsing rules, that previously compiled without any
warning, I get the same warning again.

When trying to create a simple example to post here, it seemed that the
actual parsing code (that is the only code that uses boost::bind) was
exchangeable. It was the number of options in the parsing rule that
caused the warning to appear (which I really do not understand).

The parsing rule looks like this:

parse(someString.c_str(),
(
*(
str_p('+') >> str_p('(') >> real_p[boost::bind(&Object::func_param,
boost::ref(m_curObmect), _1)] >> str_p(')') |
str_p('+')[boost::bind(&Object::func, boost::ref(m_curObject), _1)] /*|

str_p('+') >> str_p('(') >> real_p[boost::bind(&Object::func_param,
boost::ref(m_curObmect), _1)] >> str_p(')') |
str_p('+')[boost::bind(&Object::func, boost::ref(m_curObject), _1)]
[... to be repeated ...] */

)
)
,
space_p).full;

The goal is to find either "+" or "+(double)", which works as expected.
causesThe signatures of the Object functions are
Object::func_param(double param); and
Object::func(char);

The rule can be copied 7 times, leading to 14 options, without any
warning. If I add one 8th copy of these lines, or if I just add a 15th
option (independent of the actual line I copy) I get the warning again.

My system is an Ubuntu Karmic 64bit machine, using gcc 4.4.1, boost 1.39
headers and simply including "boost/spirit.hpp", which means I get the
deprecation warning for that file at the moment.

I'd be thankful for any suggestions, since for now, I do not even know
where to look further. I do not have any idea what might cause this warning.

thanks,
Norbert



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[OvermindDL1]

On Wed, Nov 4, 2009 at 1:24 AM, Norbert Wenzel <n_wenzel@...> wrote:

> Hello,
>
> I'm currently parsing some data using Spirit together with boost::bind
> to set the callbacks for Spirit. In release build I get a compiler (gcc
> 4.4.1) warning from bind:
> warning: dereferencing pointer ‘val’ does break strict-aliasing rules
>
> I was able to find the lines causing this problem by commenting them
> out, rebuilding and the error got away. The strange thing is, that when
> I copy some other parsing rules, that previously compiled without any
> warning, I get the same warning again.
>
> When trying to create a simple example to post here, it seemed that the
> actual parsing code (that is the only code that uses boost::bind) was
> exchangeable. It was the number of options in the parsing rule that
> caused the warning to appear (which I really do not understand).
>
> The parsing rule looks like this:
>
> parse(someString.c_str(),
> (
> *(
> str_p('+') >> str_p('(') >> real_p[boost::bind(&Object::func_param,
> boost::ref(m_curObmect), _1)] >> str_p(')') |
> str_p('+')[boost::bind(&Object::func, boost::ref(m_curObject), _1)] /*|
>
> str_p('+') >> str_p('(') >> real_p[boost::bind(&Object::func_param,
> boost::ref(m_curObmect), _1)] >> str_p(')') |
> str_p('+')[boost::bind(&Object::func, boost::ref(m_curObject), _1)]
> [... to be repeated ...] */
>
> )
> )
> ,
> space_p).full;
>
> The goal is to find either "+" or "+(double)", which works as expected.
> causesThe signatures of the Object functions are
> Object::func_param(double param); and
> Object::func(char);
>
> The rule can be copied 7 times, leading to 14 options, without any
> warning. If I add one 8th copy of these lines, or if I just add a 15th
> option (independent of the actual line I copy) I get the warning again.
>
> My system is an Ubuntu Karmic 64bit machine, using gcc 4.4.1, boost 1.39
> headers and simply including "boost/spirit.hpp", which means I get the
> deprecation warning for that file at the moment.
>
> I'd be thankful for any suggestions, since for now, I do not even know
> where to look further. I do not have any idea what might cause this warning.

Not sure what is causing the problem, do you have a reduced test-case
we can see?

Also, two things.
1)  You *really* should be posting this to the Spirit mailing list
instead, will get faster responses and from knowledgeable people.
2)  You *really* should be using Spirit.Qi, not Spirit.Classic.  Your
grammar's will be much shorter, much faster, and much easier.
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[Norbert Wenzel-2]

OvermindDL1 wrote:
> On Wed, Nov 4, 2009 at 1:24 AM, Norbert Wenzel <n_wenzel@...> wrote:
>>
>> I'm currently parsing some data using Spirit together with boost::bind
>> to set the callbacks for Spirit. In release build I get a compiler (gcc
>> 4.4.1) warning from bind:
>> warning: dereferencing pointer ‘val’ does break strict-aliasing rules
>
> Not sure what is causing the problem, do you have a reduced test-case
> we can see?

I could reduce the test case so much, that there was no warning anymore.
I can only reproduce the warning when using the bjam configuration, that
also builds my project. Copying the g++ parameters from the bjam build
and using them directly, does not make gcc issue any warnings. So I
guess the problem is anywhere in my build configuration, but not in the
code.

> Also, two things.
> 1)  You *really* should be posting this to the Spirit mailing list
> instead, will get faster responses and from knowledgeable people.
Sorry, I didn't know about the Spirit specific list. Next time the
questions will go there.

> 2)  You *really* should be using Spirit.Qi, not Spirit.Classic.  Your
> grammar's will be much shorter, much faster, and much easier.
Maybe I should give it a try, but I was simply finding more tutorials
faster for the classic version.

Thanks for your help.
Norbert



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