[vlc-devel] [PATCH] configure: Check if C++ headers define locale_t

[Martin Storsjö]

In environments that lack a full locale.h implementation, the C++
headers might implement some fallbacks with the same name
(on windows, libcxx does this).

In these cases, don't provide the normal fallbacks from vlc_fixups.h
when compiling in C++ mode, but include the C++ <locale> header instead.

If <locale> provides locale_t, include the header and define
HAVE_NEWLOCALE (which skips the vlc_fixups.h version of locale_t),
but keep the vlc_fixups.h fallback for uselocale. (One could
also add another configure test for whether <locale> provides
the uselocale function.)

(libcxx doesn't provide any fallback for the uselocale function
since it isn't easily implemented with the msvcrt _locale_t objects.
The libcxx fallback locale_t objects are applied via the setlocale
function, and passed to functions that take a _locale_t parameter.)
---
 configure.ac         | 12 ++++++++++++
 include/vlc_fixups.h |  5 +++++
 2 files changed, 17 insertions(+)

diff --git a/configure.ac b/configure.ac
index c03533e..0faeef9 100644
--- a/configure.ac
+++ b/configure.ac
@@ -854,6 +854,18 @@ AC_CHECK_HEADERS([features.h getopt.h linux/dccp.h linux/magic.h mntent.h sys/ev
 dnl  MacOS
 AC_CHECK_HEADERS([xlocale.h])
 
+dnl Check if C++ headers define locale_t
+AC_LANG_PUSH(C++)
+AC_CACHE_CHECK([if C++ headers define locale_t],
+  [ac_cv_cxx_locale_t],
+  [ac_cv_cxx_locale_t=no
+   AC_TRY_COMPILE([#include <locale>], [locale_t loc;],
+                    [ac_cv_cxx_locale_t=yes])])
+if test "${ac_cv_cxx_locale_t}" != "no"; then
+  AC_DEFINE(HAVE_CXX_LOCALE_T, 1, Define to 1 if C++ headers define locale_t)
+fi
+AC_LANG_POP(C++)
+
 dnl LP64 and LLP64 architectures had better define ssize_t by themselves...
 AH_TEMPLATE(ssize_t, [Define to `int' if <stddef.h> does not define.]) dnl ` (fix VIM syntax highlight
 AC_CHECK_TYPE(ssize_t,, [
diff --git a/include/vlc_fixups.h b/include/vlc_fixups.h
index 0bd8442..533cff1 100644
--- a/include/vlc_fixups.h
+++ b/include/vlc_fixups.h
@@ -314,6 +314,11 @@ void *aligned_alloc(size_t, size_t);
 # define HAVE_USELOCALE
 #endif
 
+#if !defined(HAVE_USELOCALE) && defined(HAVE_CXX_LOCALE_T) && defined(__cplusplus)
+# include <locale>
+# define HAVE_NEWLOCALE
+#endif
+
 /* locale.h */
 #ifndef HAVE_USELOCALE
 # ifndef HAVE_NEWLOCALE
-- 
2.7.4