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

[Eric Blake]

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?

> [*] 
> 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>

--
Eric Blake, Principal Software Engineer
Red Hat, Inc.           +1-919-301-3266
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