It's not necessarily safe to assume a system variable/function/header,
if available to the C compiler, is available to the C++ compiler. This
is even in the case the same vendor provides the C and C++ compiler.
For example:
1. On Tru64 UNIX 5.1, <stdint.h> is available to the C compiler,
but not the C++ compiler.
$ cat test.c
#include <stdint.h>
$ cc -c test.c
$ cp test.c test.cc
$ cxx -c test.cc
cxx: Error: test.cc, line 1: could not open source file "stdint.h"
#include <stdint.h>
-------------------^
cxx: Info: 1 error detected in the compilation of "test.cc".
2. On HP-UX 11.23/IA, <wchar.h> will bring in mbstate_t for the
C++ compiler, but not the C89 compiler.
$ cat test.c
#include <wchar.h>
$ cc -E test.c | grep mbstate_t
$ c99 -E test.c | grep mbstate_t
#line 1 "/usr/include/sys/_mbstate_t.h"
} mbstate_t;
...
$ cp test.c test.cc
$ aCC -E test.cc | grep mbstate_t
#line 1 "/usr/include/sys/_mbstate_t.h"
} mbstate_t;
...
We ran into a few problems like the above building lftp, a C++
command-line ftp client, which includes some of the gnulib modules. In
the case of #1 above, if a C++ program includes human.h, and
<stdint.h> is available, then the following code in human.h is called:
# if HAVE_STDINT_H
# include <stdint.h>
# endif
While HAVE_STDINT_H is in config.h, <stdint.h> is not available to the
C++ compiler. This caveat is specific to the compiler. The Sun C++
compiler is happy to bring in <stdint.h>.
How do we solve this? We've currently solved it by implementing
separate defines depending on the language. As an example, I've
attached our patched mbstate_t.m4 below. We've done something similar
for inttypes_h.m4, stdint_h.m4, and uintmax_t.m4. Is this the correct
approach? Ideally, we should autodetect AC_PROG_CXX and build with the
C++ compiler only if AC_PROG_CXX has been called (AC_PROVIDE_IFELSE?).
--
albert chin ([EMAIL PROTECTED])
-- snip snip
--- mbstate_t.m4.orig 2005-01-26 00:38:40.000000000 -0600
+++ mbstate_t.m4 2005-11-26 00:36:42.285226000 -0600
@@ -13,7 +13,7 @@
# AC_TYPE_MBSTATE_T
# -----------------
AC_DEFUN([AC_TYPE_MBSTATE_T],
- [AC_CACHE_CHECK([for mbstate_t], ac_cv_type_mbstate_t,
+ [AC_CACHE_CHECK([for mbstate_t under C], ac_cv_type_mbstate_t,
[AC_COMPILE_IFELSE(
[AC_LANG_PROGRAM(
[AC_INCLUDES_DEFAULT
@@ -22,9 +22,45 @@
[ac_cv_type_mbstate_t=yes],
[ac_cv_type_mbstate_t=no])])
if test $ac_cv_type_mbstate_t = yes; then
- AC_DEFINE([HAVE_MBSTATE_T], 1,
- [Define to 1 if <wchar.h> declares mbstate_t.])
+ AC_DEFINE([HAVE_C_MBSTATE_T], 1,
+ [Define to 1 if <wchar.h> under C declares mbstate_t.])
else
- AC_DEFINE([mbstate_t], int,
- [Define to a type if <wchar.h> does not define.])
- fi])
+ AC_DEFINE([c_mbstate_t], int,
+ [Define to a type if <wchar.h> under C does not define.])
+ fi
+
+ AC_CACHE_CHECK([for mbstate_t under C++], ac_cv_cxx_type_mbstate_t,
+ [AC_LANG_PUSH(C++)
+ AC_COMPILE_IFELSE(
+ [AC_LANG_PROGRAM(
+ [AC_INCLUDES_DEFAULT
+# include <wchar.h>],
+ [mbstate_t x; return sizeof x;])],
+ [ac_cv_cxx_type_mbstate_t=yes],
+ [ac_cv_cxx_type_mbstate_t=no])
+ AC_LANG_POP(C++)])
+ if test $ac_cv_cxx_type_mbstate_t = yes; then
+ AC_DEFINE([HAVE_CXX_MBSTATE_T], 1,
+ [Define to 1 if <wchar.h> under C++ declares mbstate_t.])
+ else
+ AC_DEFINE([cxx_mbstate_t], int,
+ [Define to a type if <wchar.h> under C++ does not define.])
+ fi
+
+ AH_VERBATIM([mbstate_t],
+ [/* Define to 1 if <wchar.h> declares mbstate_t. */
+#ifdef __cplusplus
+#ifdef HAVE_CXX_MBSTATE_T
+#define HAVE_MBSTATE_T 1
+#endif
+#ifdef cxx_mbstate_t
+#define mbstate_t cxx_mbstate_t
+#endif
+#else
+#ifdef HAVE_C_MBSTATE_T
+#define HAVE_MBSTATE_T 1
+#endif
+#ifdef c_mbstate_t
+#define mbstate_t c_mbstate_t
+#endif
+#endif])])
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