[Boost-users] [CRC] Compilation fails with #include <boost/crc.hpp>

From: Norbert Riedlin (norbert.riedlin_at_[hidden])
Date: 2008-07-29 03:14:25

Hi all,

I want to use boost CRC, but when I #include <boost/crc.hpp>, I get
the following error:
    "error: ISO C++ forbids variable-size array 'table_type'"
in line 468 of crc.hpp.

gcc --version tells me, I'm using the following gcc on my Mac (OSX
10.5):
    "i686-apple-darwin9-gcc-4.0.1 (GCC) 4.0.1 (Apple Inc. build 5484)"

I use boost 1.34.1, but as crc.hpp of version 1.35 does not differ, I
suppose updating the library would not help.

The error is in the following context:

<code>
    struct crc_table_t
    {
        BOOST_STATIC_CONSTANT( std::size_t,
            byte_combos = (1ul << CHAR_BIT) );

        typedef mask_uint_t<Bits>            masking_type;
        typedef typename masking_type::fast  value_type;
#if defined(__BORLANDC__) && defined(_M_IX86) && (__BORLANDC__ == 0x560)
        // for some reason Borland's command line compiler (version
        // 0x560)
        // chokes over this unless we do the calculation for it:
        typedef value_type                   table_type[ 0x100 ];
#else
        typedef value_type  table_type[ byte_combos ];//<-- error here
#endif

        static  void  init_table();

        static  table_type  table_;

    };  // boost::detail::crc_table_t
</code>

I suppose it has to do with a bug of gcc, that cannot calculate
"byte_combos" at compile time (or at least it acts as if it had to
calculate "byte_combos" at runtime). A fix would be to enhance the
"#if defined..." to the gcc versions with the said bug.

I just realized there was an entry in the bug tracking system at
sourceforge concerning this problem:

https://sourceforge.net/tracker/?func=detail&atid=107586&aid=1478435&gro
up_id=7586 

but I have no permission to view the issue. The entry was made in early
2006. Is there any work on this issue?

TIA
Norbert

P.S.: I also realize I can get around the problem by not using
"-pedantic", but for me this is a valuable switch.