* [PATCH] use strnlen in pretty printer for "%.*s" (PR 81859)
@ 2017-08-16 17:20 Martin Sebor
2017-08-16 22:38 ` David Malcolm
0 siblings, 1 reply; 3+ messages in thread
From: Martin Sebor @ 2017-08-16 17:20 UTC (permalink / raw)
To: Gcc Patch List
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Bug 81859 points out that my fix for bug 81586 wasn't quite
right (or complete): the argument of a %.*s directive need
not be a nul-terminated string when the precision is less
than the initialized size of the array the argument points
to. The attached tweak uses strnlen to avoid reading past
the end of a non-nul terminated array.
The patch has been tested on x86_64-linux and by running
self tests under Valgrind. I'll go ahead and commit it as
obvious sometime later today if there are no objections in
the meantime.
Martin
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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");
+
/* We can't test for %p; the pointer is printed in an implementation-defined
manner. */
ASSERT_PP_FORMAT_2 ("normal colored normal 12345678",
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: [PATCH] use strnlen in pretty printer for "%.*s" (PR 81859)
2017-08-16 17:20 [PATCH] use strnlen in pretty printer for "%.*s" (PR 81859) Martin Sebor
@ 2017-08-16 22:38 ` David Malcolm
2017-08-17 19:01 ` Martin Sebor
0 siblings, 1 reply; 3+ messages in thread
From: David Malcolm @ 2017-08-16 22:38 UTC (permalink / raw)
To: Martin Sebor, Gcc Patch List
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
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: [PATCH] use strnlen in pretty printer for "%.*s" (PR 81859)
2017-08-16 22:38 ` David Malcolm
@ 2017-08-17 19:01 ` Martin Sebor
0 siblings, 0 replies; 3+ messages in thread
From: Martin Sebor @ 2017-08-17 19:01 UTC (permalink / raw)
To: David Malcolm, Gcc Patch List
On 08/16/2017 02:55 PM, David Malcolm wrote:
> 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.
Sure. I committed the updated fix in r251157.
Martin
^ permalink raw reply [flat|nested] 3+ messages in thread
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2017-08-16 22:38 ` David Malcolm
2017-08-17 19:01 ` Martin Sebor
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