-dnl check for vprintf/vsprintf() which are GNU extensions
-AC_FUNC_VPRINTF
-
-dnl check for vsscanf() and vsnprintf() - on some platforms (Linux, glibc
-dnl 2.1.1 for the first one, HP-UX for the second) it's available in the
-dnl library but the prototype is missing, so we can't use AC_CHECK_FUNCS() here,
-dnl do it manually. We can't use AC_TRY_COMPILE(), either, because it doesn't
-dnl check if the symbol is available at linking time
-
-dnl we use AC_TRY_LINK() here instead of AC_TRY_RUN() to make the checks
-dnl work for cross-compilation, but AC_TRY_LINK() normally only compiles
-dnl one function while we need at least 2 - hence the ugly hack below. To
-dnl understand why it works, remember that AC_TRY_LINK() just prepends
-dnl "int main() {" in the beginning of the code and "; return 0; }" at the
-dnl end...
-
-dnl if we fail to find vsnprintf, also try for _vsnprintf as that is what
-dnl we'll find under MSW if it exists.
-
-dnl final note: AC_TRY_LINK will only be executed if there is nothing in
-dnl the cache so we have to do AC_DEFINE(HAVE_VSNPRINTF) below and not inside
-dnl it or the symbol wouldn't be defined for the 2nd and subsequent configure
-dnl runs
+dnl *printf() functions sometimes are available in the library but not
+dnl prototyped -- if this is the case, we can't use them from C++ code, but to
+dnl detect this we have to use C++ compiler for testing
+AC_LANG_SAVE
+AC_LANG_CPLUSPLUS