From 5020b14d5419065f1a5ef5aed1be7badee28c9bf Mon Sep 17 00:00:00 2001
From: Joris Peeraer
Date: Thu, 22 Oct 2020 10:38:03 +0200
Subject: py/mpprint: Fix length calculation for strings with
 precision-modifier.

Two issues are tackled:

1. The calculation of the correct length to print is fixed to treat the
   precision as a maximum length instead as the exact length.
   This is done for both qstr (%q) and for regular str (%s).

2. Fix the incorrect use of mp_printf("%.*s") to mp_print_strn().

   Because of the fix of above issue, some testcases that would print
   an embedded null-byte (^@ in test-output) would now fail.
   The bug here is that "%s" was used to print null-bytes. Instead,
   mp_print_strn is used to make sure all bytes are outputted and the
   exact length is respected.

Test-cases are added for both %s and %q with a combination of precision
and padding specifiers.
---
 py/objstrunicode.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

(limited to 'py/objstrunicode.c')

diff --git a/py/objstrunicode.c b/py/objstrunicode.c
index b21df22a3..ed79ad68a 100644
--- a/py/objstrunicode.c
+++ b/py/objstrunicode.c
@@ -92,7 +92,7 @@ STATIC void uni_print(const mp_print_t *print, mp_obj_t self_in, mp_print_kind_t
     }
     #endif
     if (kind == PRINT_STR) {
-        mp_printf(print, "%.*s", str_len, str_data);
+        print->print_strn(print->data, (const char *)str_data, str_len);
     } else {
         uni_print_quoted(print, str_data, str_len);
     }
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