new module 'c++defs'

[John W. Eaton]

On 22-Feb-2010, Bruno Haible wrote:

| Here come the proposed changes to allow C++ developers to choose among
| the default mode with many
|   #define func rpl_func
| macro definitions and a "namespace mode", which is more in line with the
| way C++ programs are built.
| 
| I handled all header files that do such #defines, except for
|   - stat and stat64 - a difficult situation, which I prefer not to touch,
|   - getopt.h - also tricky.
| 
| [...]
| 
| Opinions? Suggestions?

Thanks for working on this.

I tried your changes with the Octave sources and quickly hit this error:

  make[3]: Entering directory `/scratch/jwe/build/octave/liboctave'
  /bin/sh ../libtool  --tag=CXX   --mode=compile g++ -DHAVE_CONFIG_H -I. 
-I/home/jwe/src/octave/liboctave -I..            -I../libgnu 
-I/home/jwe/src/octave/libgnu -I/home/jwe/src/octave/libcruft/misc  -ggdb3  
-DHAVE_CONFIG_H -I/usr/include/freetype2   -Wall -W -Wshadow -Wold-style-cast 
-Wformat -ggdb3 -pthread -ggdb3 -MT liboctave_la-CollocWt.lo -MD -MP -MF 
.deps/liboctave_la-CollocWt.Tpo -c -o liboctave_la-CollocWt.lo `test -f 
'CollocWt.cc' || echo '/home/jwe/src/octave/liboctave/'`CollocWt.cc
  libtool: compile:  g++ -DHAVE_CONFIG_H -I. -I/home/jwe/src/octave/liboctave 
-I.. -I../libgnu -I/home/jwe/src/octave/libgnu 
-I/home/jwe/src/octave/libcruft/misc -ggdb3 -DHAVE_CONFIG_H 
-I/usr/include/freetype2 -Wall -W -Wshadow -Wold-style-cast -Wformat -ggdb3 
-pthread -ggdb3 -MT liboctave_la-CollocWt.lo -MD -MP -MF 
.deps/liboctave_la-CollocWt.Tpo -c /home/jwe/src/octave/liboctave/CollocWt.cc  
-fPIC -DPIC -o .libs/liboctave_la-CollocWt.o
  In file included from /usr/include/sys/ucontext.h:23,
                   from /usr/include/signal.h:359,
                   from ../libgnu/signal.h:36,
                   from /usr/include/sys/wait.h:31,
                   from /home/jwe/src/octave/liboctave/syswait.h:39,
                   from /home/jwe/src/octave/liboctave/lo-utils.h:33,
                   from /home/jwe/src/octave/liboctave/Array.h:38,
                   from /home/jwe/src/octave/liboctave/Array2.h:32,
                   from /home/jwe/src/octave/liboctave/MArray2.h:28,
                   from /home/jwe/src/octave/liboctave/dMatrix.h:27,
                   from /home/jwe/src/octave/liboctave/CollocWt.h:29,
                   from /home/jwe/src/octave/liboctave/CollocWt.cc:30:
  ../libgnu/stdio.h:1087: error: previous declaration of 'int 
_gl_cxxalias_dummy' with 'C++' linkage
  ../libgnu/signal.h:246: error: conflicts with new declaration with 'C' linkage

The following additional change avoids the trouble for me by forcing 'C'
linkage for the _gl_cxxalias_dummy symbol.

jwe

diff --git a/build-aux/c++defs.h b/build-aux/c++defs.h
index f3bc4d4..f4313bf 100644
--- a/build-aux/c++defs.h
+++ b/build-aux/c++defs.h
@@ -111,13 +111,18 @@
  */
 #define _GL_CXXALIAS_RPL(func,rettype,parameters) \
   _GL_CXXALIAS_RPL_1 (func, rpl_##func, rettype, parameters)
-#if defined __cplusplus && defined GNULIB_NAMESPACE
-# define _GL_CXXALIAS_RPL_1(func,rpl_func,rettype,parameters) \
+#if defined __cplusplus
+# if defined GNULIB_NAMESPACE
+#  define _GL_CXXALIAS_RPL_1(func,rpl_func,rettype,parameters) \
     namespace GNULIB_NAMESPACE                                \
     {                                                         \
       rettype (*const func) parameters = ::rpl_func;          \
     }                                                         \
-    extern int _gl_cxxalias_dummy
+    extern "C" int _gl_cxxalias_dummy
+# else
+#  define _GL_CXXALIAS_RPL_1(func,rpl_func,rettype,parameters) \
+    extern "C" int _gl_cxxalias_dummy
+# endif
 #else
 # define _GL_CXXALIAS_RPL_1(func,rpl_func,rettype,parameters) \
     extern int _gl_cxxalias_dummy
@@ -130,13 +135,18 @@
    Example:
      _GL_CXXALIAS_SYS (open, int, (const char *filename, int flags, ...));
  */
-#if defined __cplusplus && defined GNULIB_NAMESPACE
-# define _GL_CXXALIAS_SYS(func,rettype,parameters) \
+#if defined __cplusplus
+# if defined GNULIB_NAMESPACE
+#  define _GL_CXXALIAS_SYS(func,rettype,parameters) \
     namespace GNULIB_NAMESPACE                     \
     {                                              \
       rettype (*const func) parameters = ::func;   \
     }                                              \
-    extern int _gl_cxxalias_dummy
+    extern "C" int _gl_cxxalias_dummy
+# else
+#  define _GL_CXXALIAS_SYS(func,rettype,parameters) \
+    extern "C" int _gl_cxxalias_dummy
+# endif
 #else
 # define _GL_CXXALIAS_SYS(func,rettype,parameters) \
     extern int _gl_cxxalias_dummy