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Re: [Qemu-devel] [PATCH v3 1/5] qemu/compiler: Define QEMU_NONSTRING

From: Philippe Mathieu-Daudé
Subject: Re: [Qemu-devel] [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
>>> 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>


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