qemu/compiler: Define QEMU_NONSTRING

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>).

In tandem of -Wstringop-truncation, the "nonstring" attribute was added:

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.

From the GCC manual: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-nonstring-variable-attribute

Add the QEMU_NONSTRING macro which checks if the compiler supports this
attribute.

Backports commit 1daff2f8193496b0e5e0ab56dc48c570c81f804e from qemu
This commit is contained in:
Philippe Mathieu-Daudé 2019-01-22 15:05:55 -05:00 committed by Lioncash
parent b6cc2c4e06
commit 24c56c65a3
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@ -25,6 +25,21 @@
# define QEMU_ERROR(X)
#endif
/*
* The nonstring variable attribute specifies that an object or member
* declaration with type array of char or pointer to char is intended
* to store character arrays that do not necessarily contain a terminating
* NUL character. 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.
*/
#if __has_attribute(nonstring)
# define QEMU_NONSTRING __attribute__((nonstring))
#else
# define QEMU_NONSTRING
#endif
#ifdef _MSC_VER
// MSVC support