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[Qemu-devel] [PATCH v4 1/5] qemu/compiler: Define QEMU_NONSTRING
From: |
Philippe Mathieu-Daudé |
Subject: |
[Qemu-devel] [PATCH v4 1/5] qemu/compiler: Define QEMU_NONSTRING |
Date: |
Fri, 28 Dec 2018 18:33:52 +0100 |
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.
Suggested-by: Michael S. Tsirkin <address@hidden>
Reviewed-by: Eric Blake <address@hidden>
Reviewed-by: Michael S. Tsirkin <address@hidden>
Signed-off-by: Philippe Mathieu-Daudé <address@hidden>
---
v4: reordered the commit description to make sens (eblake)
Note this trigger the following checkpatch warning (patchew):
WARNING: architecture specific defines should be avoided
#50: FILE: include/qemu/compiler.h:163:
+#if __has_attribute(nonstring)
---
include/qemu/compiler.h | 15 +++++++++++++++
1 file changed, 15 insertions(+)
diff --git a/include/qemu/compiler.h b/include/qemu/compiler.h
index 261842beae..2d8f507c73 100644
--- a/include/qemu/compiler.h
+++ b/include/qemu/compiler.h
@@ -151,6 +151,21 @@
# 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
+
/* Implement C11 _Generic via GCC builtins. Example:
*
* QEMU_GENERIC(x, (float, sinf), (long double, sinl), sin) (x)
--
2.17.2