Nothing field in immutable occupies nonzero space

[ivarne]

https://groups.google.com/forum/#!topic/julia-users/2uXsjXuXxn0

immutable MyType{A}
    a::A
end
sizeof(MyType(nothing))
8
sizeof(MyType(int8(1)))
1
sizeof(MyType(int16(1)))
2
sizeof(MyType(int32(1)))
4

sizeof(MyType(nothing)) should be 0, shouldn't it?

cc: @mlhetland

[pao]

Renamed--the immutable type has a field, you've just given it a type that doesn't necessarily need space to represent.

[ivarne]

immutable My{A, B}
    a::A
    b::B
end
My(nothing, 1)

Now causes segfault with the following backtrace:

signal (11): Segmentation fault: 11
pool_alloc at /Users/ivarne/dev/julia/src/gc.c:507
typeinf at ./inference.jl:1367
typeinf at /Users/ivarne/dev/julia/usr/lib/julia/sys.dylib (unknown line)
jl_apply at /Users/ivarne/dev/julia/src/./julia.h:987
typeinf_ext at ./inference.jl:1220
jl_apply at /Users/ivarne/dev/julia/src/./julia.h:987
jl_apply at /Users/ivarne/dev/julia/src/gf.c:393
jl_mt_assoc_by_type at /Users/ivarne/dev/julia/src/gf.c:980
jl_apply_generic at /Users/ivarne/dev/julia/src/gf.c:1581
eval_user_input at REPL.jl:55
jlcall_eval_user_input;138356 at  (unknown line)
jl_apply at /Users/ivarne/dev/julia/src/./julia.h:987
anonymous at task.jl:96
jl_apply at /Users/ivarne/dev/julia/src/task.c:427
julia_trampoline at /Users/ivarne/dev/julia/src/init.c:1011
Segmentation fault: 11

[ivarne]

Confirmed that it did not segfault on the parent commit of 6667e5d