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Re: [Qemu-block] [PATCH v3 1/5] qemu/compiler: Define QEMU_NONSTRING
From: |
Philippe Mathieu-Daudé |
Subject: |
Re: [Qemu-block] [PATCH v3 1/5] qemu/compiler: Define QEMU_NONSTRING |
Date: |
Tue, 18 Dec 2018 20:28:38 +0100 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.3.1 |
On 12/18/18 7:29 PM, Eric Blake wrote:
> On 12/18/18 11:51 AM, Philippe Mathieu-Daudé wrote:
>> GCC 8 introduced the -Wstringop-truncation checker to detect
>> truncation by
>> the strncat and strncpy functions (closely related to
>> -Wstringop-overflow,
>> which detect buffer overflow by string-modifying functions declared in
>> <string.h>).
>
> This paragraph talks about a new warning checker, but makes no mention
> of an attribute.
>
>>
>> Add the QEMU_NONSTRING macro which checks if the compiler supports this
>> attribute.
>
> Thus, "this attribute" has no antecedent; did you forget to add a
> sentence to the previous paragraph, or maybe put the mention of adding
> QEMU_NONSTRING after...
>
>>
>>> From the GCC manual [*]:
>>
>> The nonstring variable attribute specifies that an object or member
>> declaration with type array of char, signed char, or unsigned char,
>> or pointer to such a type is intended to store character arrays that
>> do not necessarily contain a terminating NUL. This is useful in
>> detecting
>> uses of such arrays or pointers with functions that expect
>> NUL-terminated
>> strings, and to avoid warnings when such an array or pointer is
>> used as
>> an argument to a bounded string manipulation function such as strncpy.
>
> ...the explanation of how the attribute was added in tandem with the new
> warning checker for silencing specific instances of the warning?
Yes... I will rewrite this.
>
>>
>> [*]
>> https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-nonstring-variable-attribute
>>
>>
>> Suggested-by: Michael S. Tsirkin <address@hidden>
>> Signed-off-by: Philippe Mathieu-Daudé <address@hidden>
>> ---
>> include/qemu/compiler.h | 15 +++++++++++++++
>> 1 file changed, 15 insertions(+)
>>
>
> Reviewed-by: Eric Blake <address@hidden>
Thanks!