structalign prints the memory alignment of structs.
This is a fork of the structlayout, with some nicer output and more options.
For example:
% structalign net/mail.Address
struct Address, 32 bytes, 0 padding
Name string 0-16 (size 16, align 8)
Address string 16-32 (size 16, align 8)
Or to list everything in a package:
% structalign net/mail/...
struct Address, 32 bytes, 0 padding
Name string 0-16 (size 16, align 8)
Address string 16-32 (size 16, align 8)
struct AddressParser, 8 bytes, 0 padding
WordDecoder *mime.WordDecoder 0-8 (size 8, align 8)
struct Message, 24 bytes, 0 padding
Header net/mail.Header 0-8 (size 8, align 8)
Body io.Reader 8-24 (size 16, align 8)
struct addrParser, 24 bytes, 0 padding
s string 0-16 (size 16, align 8)
dec *mime.WordDecoder 16-24 (size 8, align 8)
struct dateLayoutsBuildOnce, 12 bytes, 0 padding
_ sync.noCopy 0-0 (size 0, align 1)
done._ sync/atomic.noCopy 0-0 (size 0, align 1)
done.v uint32 0-4 (size 4, align 4)
m._ sync.noCopy 4-4 (size 0, align 1)
m.mu.state int32 4-8 (size 4, align 4)
m.mu.sema uint32 8-12 (size 4, align 4)
struct rfc2047Decoder, 8 bytes, 0 padding
CharsetReader func(…) 0-8 (size 8, align 8)
Or to only list structs with extra padding:
% structalign regexp/... -with-padding
struct regexp.Regexp, 160 bytes, 13 padding, can save 8 bytes
expr string 0-16 (size 16, align 8)
prog *regexp/syntax.Prog 16-24 (size 8, align 8)
onepass *regexp.onePassProg 24-32 (size 8, align 8)
numSubexp int 32-40 (size 8, align 8)
maxBitStateLen int 40-48 (size 8, align 8)
subexpNames []string 48-72 (size 24, align 8)
prefix string 72-88 (size 16, align 8)
prefixBytes []byte 88-112 (size 24, align 8)
prefixRune rune 112-116 (size 4, align 4)
prefixEnd uint32 116-120 (size 4, align 4)
mpool int 120-128 (size 8, align 8)
matchcap int 128-136 (size 8, align 8)
prefixComplete bool 136-137 (size 1, align 1)
cond regexp/syntax.EmptyOp 137-138 (size 1, align 1)
_ «padding» 138-144 (size 6, align 0)
minInputLen int 144-152 (size 8, align 8)
longest bool 152-153 (size 1, align 1)
_ «padding» 153-160 (size 7, align 0)
struct regexp.machine, 240 bytes, 14 padding, can save 8 bytes
re *regexp.Regexp 0-8 (size 8, align 8)
p *regexp/syntax.Prog 8-16 (size 8, align 8)
q0.sparse []uint32 16-40 (size 24, align 8)
q0.dense []regexp.entry 40-64 (size 24, align 8)
q1.sparse []uint32 64-88 (size 24, align 8)
q1.dense []regexp.entry 88-112 (size 24, align 8)
pool []*regexp.thread 112-136 (size 24, align 8)
matched bool 136-137 (size 1, align 1)
_ «padding» 137-144 (size 7, align 0)
matchcap []int 144-168 (size 24, align 8)
inputs.bytes.str []byte 168-192 (size 24, align 8)
inputs.string.str string 192-208 (size 16, align 8)
inputs.reader.r io.RuneReader 208-224 (size 16, align 8)
inputs.reader.atEOT bool 224-225 (size 1, align 1)
_ «padding» 225-232 (size 7, align 0)
inputs.reader.pos int 232-240 (size 8, align 8)
