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Re: [PATCH] use strnlen in pretty printer for "%.*s" (PR 81859)
- From: David Malcolm <dmalcolm at redhat dot com>
- To: Martin Sebor <msebor at gmail dot com>, Gcc Patch List <gcc-patches at gcc dot gnu dot org>
- Date: Wed, 16 Aug 2017 16:55:24 -0400
- Subject: Re: [PATCH] use strnlen in pretty printer for "%.*s" (PR 81859)
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On Wed, 2017-08-16 at 10:12 -0600, Martin Sebor wrote:
> PR c/81859 - [8 Regression] valgrind error from
> warn_about_normalization
>
> gcc/ChangeLog:
>
> PR c/81859
> * pretty-print.c (pp_format): Use strnlen in %.*s to avoid
> reading
> past the end of an array.
> (test_pp_format): Add test cases.
>
> Index: gcc/pretty-print.c
> ===================================================================
> --- gcc/pretty-print.c (revision 251100)
> +++ gcc/pretty-print.c (working copy)
> @@ -668,15 +668,11 @@ pp_format (pretty_printer *pp, text_info *text)
>
> s = va_arg (*text->args_ptr, const char *);
>
> - /* Negative precision is treated as if it were
> omitted. */
> - if (n < 0)
> - n = INT_MAX;
> + /* Append the lesser of precision and strlen (s)
> characters
> + from the array (which need not be a nul-terminated
> string).
> + Negative precision is treated as if it were
> omitted. */
> + size_t len = n < 0 ? strlen (s) : strnlen (s, n);
>
> - /* Append the lesser of precision and strlen (s)
> characters. */
> - size_t len = strlen (s);
> - if ((unsigned) n < len)
> - len = n;
> -
> pp_append_text (pp, s, s + len);
> }
> break;
> @@ -1438,6 +1434,13 @@ test_pp_format ()
> ASSERT_PP_FORMAT_2 ("A 12345678", "%c %x", 'A', 0x12345678);
> ASSERT_PP_FORMAT_2 ("hello world 12345678", "%s %x", "hello
> world",
> 0x12345678);
> +
> + /* Not nul-terminated. */
> + char arr[5] = { '1', '2', '3', '4', '5' };
> + ASSERT_PP_FORMAT_2 ("123", "%.*s", 3, arr);
> + ASSERT_PP_FORMAT_2 ("1234", "%.*s", -1, "1234");
> + ASSERT_PP_FORMAT_2 ("12345", "%.*s", 7, "12345");
> +
The other examples in this selftest append a trailing argument with a
known bit pattern (0x12345678), to ensure that we're consuming
arguments correctly.
Please can you do the same for these tests.
Thanks
Dave