extern "C" for wctype.h?

[John W. Eaton]

An Octave user reported the following link error when building Octave
on a Windows system with MinGW:

  libtool: compile:  g++ -shared-libgcc -DHAVE_CONFIG_H -I. 
-I../../../hg/octave-work/liboctave -I..
  -Ic:/Programs/OctaveBuild/include -Ic:/Programs/WinDevTools/include 
-Ic:/Programs/GnuWin32/include
  -IC:/Programs/GnuWin32/include -I../libgnu -I../../../hg/octave-work/libgnu
  -I../../../hg/octave-work/libcruft/misc -Ic:/Programs/OctaveBuild/include
  -Ic:/Programs/WinDevTools/include -Ic:/Programs/GnuWin32/include 
-IC:/Programs/GnuWin32/include -O3
  -fomit-frame-pointer -DHAVE_CONFIG_H -mieee-fp 
-I/WinDevTools/bin/../include/freetype2
  -I/WinDevTools/bin/../include -IC:/Programs/WinDevTools/include -Wall -W 
-Wshadow -Wold-style-cast
  -Wformat -O3 -fomit-frame-pointer -O3 -fomit-frame-pointer -MT 
liboctave_la-CollocWt.lo -MD -MP -MF
  .deps/liboctave_la-CollocWt.Tpo -c 
../../../hg/octave-work/liboctave/CollocWt.cc  -DDLL_EXPORT -DPIC
  -o .libs/liboctave_la-CollocWt.o

  In file included from 
c:\programs\mingw\bin\../lib/gcc/mingw32/4.4.0/include/c++/cctype:44,
                   from 
c:\programs\mingw\bin\../lib/gcc/mingw32/4.4.0/include/c++/bits/localefwd.h:44,
                   from 
c:\programs\mingw\bin\../lib/gcc/mingw32/4.4.0/include/c++/ios:42,
                   from 
c:\programs\mingw\bin\../lib/gcc/mingw32/4.4.0/include/c++/ostream:40,
                   from 
c:\programs\mingw\bin\../lib/gcc/mingw32/4.4.0/include/c++/iostream:40,
                   from ../../../hg/octave-work/liboctave/CollocWt.cc:28:
  ../libgnu/wctype.h:218: error: previous declaration of 'wint_t 
rpl_towlower(wint_t)' with 'C++'
  linkage
  
c:\programs\mingw\bin\../lib/gcc/mingw32/4.4.0/../../../../include/ctype.h:215: 
error: conflicts with
  new declaration with 'C' linkage
  ../libgnu/wctype.h:225: error: previous declaration of 'wint_t 
rpl_towupper(wint_t)' with 'C++'
  linkage
  
c:\programs\mingw\bin\../lib/gcc/mingw32/4.4.0/../../../../include/ctype.h:216: 
error: conflicts with
  new declaration with 'C' linkage

Adding an extern "C" block around the function declarations in
ctype.in.h as in the attached patch solved the problem.

Note that Octave is not including wctype.h directly, but via the C++
header cctype, so I would expect this to work without needing to
surround the #include statement in the Octave sources with extern "C".

jwe

>From 9c5eb4db02eaae3b8d2dc65a2a2c7e42b8aa8694 Mon Sep 17 00:00:00 2001
From: John W. Eaton <address@hidden>
Date: Thu, 7 Jan 2010 02:03:16 -0500
Subject: [PATCH] wctype.in.h: add extern "C" block for C++

---
 ChangeLog       |    4 ++++
 lib/wctype.in.h |    8 ++++++++
 2 files changed, 12 insertions(+), 0 deletions(-)

diff --git a/ChangeLog b/ChangeLog
index 92973cb..edd55bf 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,7 @@
+2010-01-07  John W. Eaton  <address@hidden>
+
+       * lib/wctype.in.h: Add extern "C" block for C++.
+
 2010-01-06  Eric Blake  <address@hidden>
 
        maint.mk: detect incorrect GFDL usage
diff --git a/lib/wctype.in.h b/lib/wctype.in.h
index 01a0779..7e8b090 100644
--- a/lib/wctype.in.h
+++ b/lib/wctype.in.h
@@ -62,6 +62,10 @@
 # endif
 #endif
 
+#ifdef __cplusplus
+extern "C" {
+#endif
+
 /* FreeBSD 4.4 to 4.11 has <wctype.h> but lacks the functions.
    Linux libc5 has <wctype.h> and the functions but they are broken.
    Assume all 12 functions are implemented the same way, or not at all.  */
@@ -227,5 +231,9 @@ rpl_towupper (wint_t wc)
 
 # endif
 
+#ifdef __cplusplus
+}
+#endif
+
 #endif /* _GL_WCTYPE_H */
 #endif /* _GL_WCTYPE_H */
-- 
1.6.5