overflow: Provide constant expression struct_size

[sfrench/cifs-2.6.git] / include / linux / overflow.h

diff --git a/include/linux/overflow.h b/include/linux/overflow.h
index 59d7228104d0211d8ffb4cd330b9cf6d01992270..f1221d11f8e57a7dfe9c33dd6363b5875ef6b796 100644 (file)
--- a/include/linux/overflow.h
+++ b/include/linux/overflow.h
@@ -4,6 +4,7 @@
 
 #include <linux/compiler.h>
 #include <linux/limits.h>
+#include <linux/const.h>
 
 /*
  * We need to compute the minimum and maximum values representable in a given
@@ -221,8 +222,9 @@ static inline size_t __must_check size_sub(size_t minuend, size_t subtrahend)
  * Return: number of bytes needed or SIZE_MAX on overflow.
  */
 #define flex_array_size(p, member, count)                              \
-       size_mul(count,                                                 \
-                sizeof(*(p)->member) + __must_be_array((p)->member))
+       __builtin_choose_expr(__is_constexpr(count),                    \
+               (count) * sizeof(*(p)->member) + __must_be_array((p)->member),  \
+               size_mul(count, sizeof(*(p)->member) + __must_be_array((p)->member)))
 
 /**
  * struct_size() - Calculate size of structure with trailing flexible array.
@@ -237,6 +239,8 @@ static inline size_t __must_check size_sub(size_t minuend, size_t subtrahend)
  * Return: number of bytes needed or SIZE_MAX on overflow.
  */
 #define struct_size(p, member, count)                                  \
-       size_add(sizeof(*(p)), flex_array_size(p, member, count))
+       __builtin_choose_expr(__is_constexpr(count),                    \
+               sizeof(*(p)) + flex_array_size(p, member, count),       \
+               size_add(sizeof(*(p)), flex_array_size(p, member, count)))
 
 #endif /* __LINUX_OVERFLOW_H */