[eclipse-clp-users] C++ interface and GCC 4.x

From: Chris Mears <cmears_at_...44...>
Date: Tue, 10 Feb 2009 10:14:32 +1100
Hello all,

The C++ interface doesn't work with recent versions of GCC using the
default options.  For example, trying to compile the eg_cc_main.cc file
(one of the examples included with Eclipse) results in the following
errors:

$ g++-4.1 eg_cc_main.cc -I${ECLIPSEDIR}/include/${ARCH} -L${ECLIPSEDIR}/lib/${ARCH} -leclipse
eg_cc_main.cc: In function ‘int main()’:
eg_cc_main.cc:55: error: ‘newvar’ was not declared in this scope
eg_cc_main.cc:59: error: ‘list’ was not declared in this scope
eg_cc_main.cc:59: error: ‘list’ was not declared in this scope
eg_cc_main.cc:59: error: declaration of ‘<typeprefixerror>list’
eg_cc_main.cc:59: error: conflicts with previous declaration ‘<typeprefixerror>list’

The result is similar for g++-4.2 and g++-4.3.  The compilation succeeds
with g++-3.3.

The problem is due to a change explained here:
http://gcc.gnu.org/gcc-4.1/changes.html , as the first point in the C++
section.  Specifically:

    ARM-style name-injection of friend declarations is no longer the
    default. For example:

          struct S {
            friend void f();
          };
          void g() { f(); }

    will not be accepted; instead a declaration of f will need to be
    present outside of the scope of S. The new -ffriend-injection option
    will enable the old behavior.

Indeed, using the -ffriend-injection option does make Eclipse's C++
interface work properly.

The proper fix, I think, is to add declarations for functions like
newvar, list etc. to Eclipse's C++ header file.  In the meantime, adding
-ffriend-injection is a fine workaround.


Chris Mears
Received on Mon Feb 09 2009 - 23:30:03 CET

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