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Diffstat (limited to 'Documentation/process')
| -rw-r--r-- | Documentation/process/deprecated.rst | 26 |
1 files changed, 26 insertions, 0 deletions
diff --git a/Documentation/process/deprecated.rst b/Documentation/process/deprecated.rst index c8fd53a11a20..f91b8441f2ef 100644 --- a/Documentation/process/deprecated.rst +++ b/Documentation/process/deprecated.rst @@ -346,3 +346,29 @@ struct_size() and flex_array_size() helpers:: instance->count = count; memcpy(instance->items, source, flex_array_size(instance, items, instance->count)); + +There are two special cases of replacement where the DECLARE_FLEX_ARRAY() +helper needs to be used. (Note that it is named __DECLARE_FLEX_ARRAY() for +use in UAPI headers.) Those cases are when the flexible array is either +alone in a struct or is part of a union. These are disallowed by the C99 +specification, but for no technical reason (as can be seen by both the +existing use of such arrays in those places and the work-around that +DECLARE_FLEX_ARRAY() uses). For example, to convert this:: + + struct something { + ... + union { + struct type1 one[0]; + struct type2 two[0]; + }; + }; + +The helper must be used:: + + struct something { + ... + union { + DECLARE_FLEX_ARRAY(struct type1, one); + DECLARE_FLEX_ARRAY(struct type2, two); + }; + }; |