Re: [Boost-users] Patch for building Boost with GCC 4.4.0

On Wed, Jun 18, 2008 at 6:03 PM, Chris Fairles wrote:

On Wed, Jun 18, 2008 at 11:18 AM, Frank Mori Hess wrote:

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On Wednesday 18 June 2008 08:52 am, Chris Fairles wrote:

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On Wed, Jun 18, 2008 at 8:51 AM, Chris Fairles wrote:

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GCC changed the way #elif's are handled (is now more std-compliant apparently) but this broke all the #elif BOOST_PP_ITERATION_DEPTH() == N lines. They need to be replaced with

#elif defined(BOOST_PP_ITERATION_DEPTH) #if BOOST_PP_ITERATION_DEPTH == N ... #endif

Does it work if you do

#elif defined(BOOST_PP_ITERATION_DEPTH) && BOOST_PP_ITERATION_DEPTH() == N

then you could avoid adding the extra #endif -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.6 (GNU/Linux)

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Unfortunately no. I thought at first it would, but gcc 4.4 still complains. Reading the std (albeit, n2606, the c++0x draft) it seems this is incorrect since the tokens after the pp directive combine to form a constant-expression and constant-expressions can be short circuited. There may be some special rule for the logical && in pp const-exprs saying that sub-expressions can be evaluated out of order, but I couldn't find anything.

I'm wrong. It's correctly erroring because: #elif 0 && () == 1 isn't a valid constant expression. Chris