>From the GCC manual:
nonstring
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.
https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html
This attribute can be used for documentation purposes (i.e. replacing
comments), but it is most helpful when the following warnings are enabled:
-Wstringop-overflow
Warn for calls to string manipulation functions such as memcpy and
strcpy that are determined to overflow the destination buffer.
[...]
-Wstringop-truncation
Warn for calls to bounded string manipulation functions such as
strncat, strncpy, and stpncpy that may either truncate the copied
string or leave the destination unchanged.
[...]
In situations where a character array is intended to store a sequence
of bytes with no terminating NUL such an array may be annotated with
attribute nonstring to avoid this warning. Such arrays, however,
are not suitable arguments to functions that expect NUL-terminated
strings. To help detect accidental misuses of such arrays GCC issues
warnings unless it can prove that the use is safe.
https://gcc.gnu.org/onlinedocs/gcc/Warning-Options.html
Signed-off-by: Miguel Ojeda <miguel.ojeda.sandonis@xxxxxxxxx>
---
include/linux/compiler_attributes.h | 14 ++++++++++++++
1 file changed, 14 insertions(+)
diff --git a/include/linux/compiler_attributes.h b/include/linux/compiler_attributes.h
index f0f9fc398440..6b28c1b7310c 100644
--- a/include/linux/compiler_attributes.h
+++ b/include/linux/compiler_attributes.h
@@ -34,6 +34,7 @@
# define __GCC4_has_attribute___externally_visible__ 1
# define __GCC4_has_attribute___noclone__ 1
# define __GCC4_has_attribute___optimize__ 1
+# define __GCC4_has_attribute___nonstring__ 0
# define __GCC4_has_attribute___no_sanitize_address__ (__GNUC_MINOR__ >= 8)
#endif
@@ -181,6 +182,19 @@
*/
#define noinline __attribute__((__noinline__))
+/*
+ * Optional: only supported since gcc >= 8
+ * Optional: not supported by clang
+ * Optional: not supported by icc
+ *
+ * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-nonstring-variable-attribute
+ */
+#if __has_attribute(__nonstring__)
+# define __nonstring __attribute__((__nonstring__))
+#else
+# define __nonstring
+#endif
+
/*
* gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-noreturn-function-attribute
* clang: https://clang.llvm.org/docs/AttributeReference.html#noreturn
--
2.17.1
