diff options
Diffstat (limited to 'src/lib')
| -rw-r--r-- | src/lib/cc/compat_compiler.h | 12 |
1 files changed, 12 insertions, 0 deletions
diff --git a/src/lib/cc/compat_compiler.h b/src/lib/cc/compat_compiler.h index 67d945cfaf..c631a7e821 100644 --- a/src/lib/cc/compat_compiler.h +++ b/src/lib/cc/compat_compiler.h @@ -253,6 +253,18 @@ */ #define STRUCT_VAR_P(st, off) ((void*) ( ((char*)(st)) + (off) ) ) +/** Macro: yield a pointer to an enclosing structure given a pointer to + * a substructure at offset <b>off</b>. Example: + * <pre> + * struct base { ... }; + * struct subtype { int x; struct base b; } x; + * struct base *bp = &x.base; + * struct *sp = SUBTYPE_P(bp, struct subtype, b); + * </pre> + */ +#define SUBTYPE_P(p, subtype, basemember) \ + ((void*) ( ((char*)(p)) - offsetof(subtype, basemember) )) + /** Macro: Yields the number of elements in array x. */ #define ARRAY_LENGTH(x) ((sizeof(x)) / sizeof(x[0])) |