py/mpprint: Fail an assertion with unsupported format specifiers.
Arguments of an unknown type cannot be skipped and continuing to parse a
format string after encountering an unknown format specifier leads to
undefined behaviour. This patch helps to find use of unsupported formats.
diff --git a/py/mpprint.c b/py/mpprint.c
index cb49b12..97ea33a 100644
--- a/py/mpprint.c
+++ b/py/mpprint.c
@@ -537,10 +537,12 @@
chrs += mp_print_int(print, arg_value, *fmt == 'd', 10, 'a', flags, fill, width);
break;
}
- // fall through to default case to print unknown format char
+ assert(!"unsupported fmt char");
}
#endif
default:
+ // if it's not %% then it's an unsupported format character
+ assert(*fmt == '%' || !"unsupported fmt char");
print->print_strn(print->data, fmt, 1);
chrs += 1;
break;