[Boost-users] [labmda & function] strange assembly errors with an unsupported compiler

From: Server Levent Yilmaz (leventyilmaz_at_[hidden])
Date: 2007-01-07 16:39:41

Hi All,

This is an anomaly I experienced with Portland Group C++ compiler. Well OK,
Boost doesn't support this compiler...  But so far for Lambda and Function
libraries I was able to run all of the tests in the 1-33-1 distribution with
success, and it seems pgCC is doing a real good job.

There is this one exception though: pgCC generates assembly errors on this
arguably weird code that I have. gcc, msvc and hpCC worked fine... So
obviously this seems to be an issue for PG itself and not Boost;  but the
code under question is really a bit weird and I am not 100% sure if it is
correct use of boost or even C++. Before I carry on with bug reports to PG
I'd like to ask for your suggestions on it...

Here is the code. Briefly, a boost::function is being passed to some
function template that expects a functor to apply on its second argument.
Another level of indirection is added where the boost::function itself is
generated from a lambda expression inside another function. I wasn't able to
narrow it down any further.. (highlighted code is here:
http://rafb.net/p/28TknK25.html) (compiler error messages follow)

// ========================================
#include <boost/function.hpp>
#include <boost/lambda/lambda.hpp>
#include <boost/lambda/bind.hpp>
#include <boost/lambda/casts.hpp>
#include <iostream>

// Some struct of only double members
struct A
{
  double a;
  double b;
};

// The "complicated" function that expect a functor to
// operate on an instance of A
template< class Func > void foo(const Func& f, const A& a)
{
  std::cout << f(a) << std::endl;
}

// A function object generator.
// It returns a functor which in turn returns some
// double member of A accessed via address offset
boost::function<double(const A&)> getmem
(
const A* obj,
 const double* mem
)
{
  ptrdiff_t shift = mem -
     reinterpret_cast<const double*>(obj);
  using namespace boost::lambda;
  return *(ll_reinterpret_cast<const double*>(&_1)
   + constant(shift) );
}

//
int main()
{
  A obj;
   obj.a = 1.;
  obj.b = 2.;
  //
  foo( getmem(&obj, &obj.b), obj );
  return 0;
}

 // wherever this compiles, it prints out "2".
// ==========================================

Here is the compiler output:
PGCC-W-0155-No va_start() seen
(/opt/pgi/6.1.4/linux86-64/6.1/include/CC/iostream: 689)
PGCC/x86 Linux/x86-64 6.1-4: compilation completed with warnings
/tmp/pgCCbaaaasxqap.s: Assembler messages:
/tmp/pgCCbaaaasxqap.s:2499: Error: junk `(%rbx)' after expression
/tmp/pgCCbaaaasxqap.s:2500: Error: junk `(%rbx)' after expression

The assembly lines under question is pasted here:
http://rafb.net/p/LW5IX765.html -- lines 7 and 8.
 The va_start() warning is probably irrelevant (this is not the only place I
have seen it, and never failed before with these warnings)

any guidance will be appreciated,

thanks

-- 
Server Levent Yilmaz
Mechanical Engineering @ PITT