When using cgo to generate Go structs, some fields are ignored in the definition.

[飞舟]

I have a C struct, and when I use cgo to generate Go structs, some fields are being ignored. I’m using go version go1.21.1 linux/amd64, and here is my env.

go env:

GO111MODULE='on'
GOARCH='amd64'
GOBIN=''
GOCACHE='/root/.cache/go-build'
GOENV='/root/.config/go/env'
GOEXE=''
GOEXPERIMENT=''
GOFLAGS=''
GOHOSTARCH='amd64'
GOHOSTOS='linux'
GOINSECURE=''
GOMODCACHE='/root/go/pkg/mod'
GONOPROXY=''
GONOSUMDB=''
GOOS='linux'
GOPATH='/root/go'
GOPRIVATE=''
GOPROXY='https://goproxy.cn,direct'
GOROOT='/usr/local/go'
GOSUMDB='sum.golang.org'
GOTMPDIR=''
GOTOOLCHAIN='auto'
GOTOOLDIR='/usr/local/go/pkg/tool/linux_amd64'
GOVCS=''
GOVERSION='go1.21.1'
GCCGO='gccgo'
GOAMD64='v1'
AR='ar'
CC='gcc'
CXX='g++'
CGO_ENABLED='1'
GOMOD='/dev/null'
GOWORK=''
CGO_CFLAGS='-O2 -g'
CGO_CPPFLAGS=''
CGO_CXXFLAGS='-O2 -g'
CGO_FFLAGS='-O2 -g'
CGO_LDFLAGS='-O2 -g'
PKG_CONFIG='pkg-config'
GOGCCFLAGS='-fPIC -m64 -pthread -Wl,--no-gc-sections -fmessage-length=0 -ffile-prefix-map=/tmp/go-build2970417006=/tmp/go-build -gno-record-gcc-switches'

and this is my C struct:

typedef struct PicHead

{

unsigned short flag;

unsigned char version[16];

unsigned int headSize;

int64_t fileSize;

unsigned int macrograph;

unsigned int personInfor;

unsigned int hierarchy;

unsigned int srcWidth;

unsigned int srcHeight;

unsigned int sliceWidth;

unsigned int sliceHeight;

unsigned int thumbnailWidth;

unsigned int thumbnailHeight;

unsigned char bpp;

unsigned char quality;

J_COLOR_SPACE colrSpace;

float scale;

double ruler;

unsigned int rate;

long long extraOffset;

long long tileOffset;

ImageFormat sliceFormat;

unsigned char headSpace[48];

}PicHead;

this is cgo gen

type _Ctype_struct_PicHead struct {

flag _Ctype_ushort

version [16]_Ctype_uchar

_ [40]byte

bpp _Ctype_uchar

quality _Ctype_uchar

colrSpace _Ctype_J_COLOR_SPACE

scale _Ctype_float

_ [8]byte

rate _Ctype_uint

extraOffset _Ctype_longlong

tileOffset _Ctype_longlong

sliceFormat _Ctype_ImageFormat

headSpace [48]_Ctype_uchar

}

[peterGo]

Repeat of post on Stack Overflow:   

https://stackoverflow.com/questions/78786971/why-do-some-fields-in-the-go-structs-generated-using-cgo-become-anonymous

[Ian Lance Taylor]

On Wed, Jul 24, 2024 at 5:29 AM 飞舟 <zev...@gmail.com> wrote:
>
> I have a C struct, and when I use cgo to generate Go structs, some fields are being ignored. I’m using go version go1.21.1 linux/amd64, and here is my env.

Please post code as plain text, rather than with a background. Plain
text is much easier to read. Thanks.

Also, please show us a complete, small, example. I tried your
example. I had to invent types for J_COLOR_SPACE and ImageFormat. It
worked fine.

Does your actual code use anything like #pragma packed? That will
cause this kind of problem, as Go does not currently have any way to
represent a packed struct.

Ian