diff options
Diffstat (limited to 'txr.1')
| -rw-r--r-- | txr.1 | 30 |
1 files changed, 27 insertions, 3 deletions
@@ -81254,11 +81254,11 @@ operator has no semantics other than these behaviors. .IP 1. When .meta type -is a +is .code struct or -.codn union , -then the +.code union +syntax which defines at least one member, then the .code pack operator performs the following syntactic transformation: each member of @@ -81292,6 +81292,30 @@ An important rationale also is that the GNU C attribute works this way, and so C structures declarations using that attribute are easier to translate to the \*(TL FFI type system. +Deriving a less strictly aligned version of a structure or union type without +any effect on the alignment of its members may be obtained by applying the +.code bit +operator to either +.code typedef +name for a structure or union type, or else to syntax which refers +to an existing type without defining members. +Given the definition +.codn "(typedef s (struct s (a int) (b char)))" , +the type +.code s +is an eight byte structure with three bytes of padding at the end, which has +four byte alignment. The type expression +.code "(pack s)" +produces a version of this type which has one byte alignment. +The expression +.codn "(pack (struct s))" , +likewise. The resulting +unaligned type is still eight bytes wide, and has three padding bytes. +In other words, the +.code pack +operator does not transform the syntax of a structure which is already +defined as an object, + .IP 2. When .meta type |