libdpkg: Fallback to use ASCII method for multibyte strings on error

We cannot do strict error checking on multibyte conversion at this
point in time, because supposedly the database is in UTF-8, but the
current locale might be in a different encoding, so the conversion
might fail due to that. It could also fail if the user requested a
standard locale like C or POSIX which does not support handling
UTF-8 encodings.

Regression introduced in commit ab5bdc1fc7bbf225efcbb3376ed309015682e772.

Reported-by: Raphaël Hertzog <hertzog@debian.org>

lib/dpkg/strwide.c

@@ -55,9 +55,16 @@ str_width(const char *str)
 	memset(&state, 0, sizeof(state));
 
 	res = mbsrtowcs(wcs, &mbs, len, &state);
-	if (res == (size_t)-1)
+	if (res == (size_t)-1) {
+#ifdef DPKG_UNIFORM_ENCODING
 		ohshit(_("cannot convert multibyte string '%s' "
 		         "to a wide-character string"), str);
+#else
+		/* Cannot convert, fallback to ASCII method. */
+		free(wcs);
+		return strlen(str);
+#endif
+	}
 
 	width = wcswidth(wcs, res);
 
@@ -101,9 +108,16 @@ str_gen_crop(const char *str, int max_width, struct str_crop_info *crop)
 		size_t mb_bytes;
 
 		mb_bytes = mbrtowc(&wc, str, str_bytes, &state);
-		if (mb_bytes == (size_t)-1 || mb_bytes == (size_t)-2)
+		if (mb_bytes == (size_t)-1 || mb_bytes == (size_t)-2) {
+#ifdef DPKG_UNIFORM_ENCODING
 			ohshit(_("cannot convert multibyte sequence '%s' "
 			         "to a wide character"), str);
+#else
+			/* Cannot convert, fallback to ASCII method. */
+			crop->str_bytes = crop->max_bytes = max_width;
+			return;
+#endif
+		}
 		if (mb_bytes == 0)
 			break;