Add check for swprintf() and a workaround when it is missing

We use this function once in our codebase, but fortunately the workaround is
relatively easy. swprintf() is not available on Cygwin so the compile failed
there, but we can do a series of mbstowcs() calls that produce the same end
result as the swprintf() call.

Signed-off-by: Dan McGee <dan@archlinux.org>

configure.ac

@@ -161,8 +161,8 @@ AC_FUNC_FORK
 AC_FUNC_LSTAT_FOLLOWS_SLASHED_SYMLINK
 AC_FUNC_MKTIME
 AC_TYPE_SIGNAL
-AC_CHECK_FUNCS([realpath regcomp strcasecmp strdup strerror strnlen \
-								strndup strrchr strsep strstr strverscmp uname geteuid])
+AC_CHECK_FUNCS([geteuid realpath regcomp strcasecmp strdup strerror \
+								strndup strrchr strsep strstr strverscmp swprintf uname])
 
 # Enable large file support if available
 AC_SYS_LARGEFILE

src/pacman/callback.c

@@ -393,7 +393,17 @@ void cb_trans_progress(pmtransprog_t event, const char *pkgname, int percent,
 	len = strlen(opr) + ((pkgname) ? strlen(pkgname) : 0) + 2;
 	wcstr = calloc(len, sizeof(wchar_t));
 	/* print our strings to the alloc'ed memory */
+#if defined(HAVE_SWPRINTF)
 	wclen = swprintf(wcstr, len, L"%s %s", opr, pkgname);
+#else
+	/* because the format string was simple, we can easily do this without
+	 * using swprintf, although it is probably not as safe/fast. The max
+	 * chars we can copy is decremented each time by subtracting the length
+	 * of the already printed/copied wide char string. */
+	wclen = mbstowcs(wcstr, opr, len);
+	wclen += mbstowcs(wcstr + wclen, " ", len - wclen);
+	wclen += mbstowcs(wcstr + wclen, pkgname, len - wclen);
+#endif
 	wcwid = wcswidth(wcstr, wclen);
 	padwid = textlen - wcwid;
 	/* if padwid is < 0, we need to trim the string so padwid = 0 */