gdb golang View the internal structure of iface

Environmental description

macOs bigSur 11.4
GNU gdb (GDB) 10.2

Code preparation

package main

type Ner interface {
    a()
    b(int)
    c(string) string
}

type N int

func (N) a() {
}

func (*N) b(i int) {
    return
}

func (*N) c(s string) string {
    return "c"
}

func main() {
    var n N
    var t Ner = &n
    t.a()
}

Command execution

go build -gcflags "-N -l" -ldflags=-compressdwarf=false main.go
gdb main

Normal output

Note that you must have: Loading Go Runtime support.

deMacBook-Pro:debugGDB de$ gdb main
GNU gdb (GDB) 10.2
Copyright (C) 2021 Free Software Foundation, Inc.
License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>
This is free software: you are free to change and redistribute it.
There is NO WARRANTY, to the extent permitted by law.
Type "show copying" and "show warranty" for details.
This GDB was configured as "x86_64-apple-darwin20.3.0".
Type "show configuration" for configuration details.
For bug reporting instructions, please see:
<https://www.gnu.org/software/gdb/bugs/>.
Find the GDB manual and other documentation resources online at:
    <http://www.gnu.org/software/gdb/documentation/>.

For help, type "help".
Type "apropos word" to search for commands related to "word"...
Reading symbols from main...
Loading Go Runtime support.
(gdb) 

1. Set a breakpoint (on line 25), and then execute

(gdb) b main.go:25

Loading Go Runtime support.
(gdb) b main.go:25
Breakpoint 1 at 0x1054d98: file /Users/didi/GolandProjects/goLarnNote/Chapter7/Iface/debugGDB/main.go, line 25.
(gdb) run
Starting program: /Users/didi/GolandProjects/goLarnNote/Chapter7/Iface/debugGDB/main 
[New Thread 0x2603 of process 72590]
[New Thread 0x1a03 of process 72590]
warning: unhandled dyld version (17)
[New Thread 0x2403 of process 72590]
[New Thread 0x2507 of process 72590]
[New Thread 0x2203 of process 72590]

Thread 2 hit Breakpoint 1, main.main () at /Users/didi/GolandProjects/goLarnNote/Chapter7/Iface/debugGDB/main.go:25
25              t.a()

2. View information and print

(gdb) info locals
t = {tab = 0x1076b60 <N,main.Ner>, data = 0xc00003c748}
n = 0
(gdb) set print pretty on
(gdb) p *t.tab.inter
$10 = {
  typ = {
    size = 16,
    ptrdata = 16,
    hash = 1801897693,
    tflag = 7 '\a',
    align = 8 '\b',
    fieldAlign = 8 '\b',
    kind = 20 '\024',
    equal = {void (void *, void *, bool *)} 0x105b818 <type.*+26936>,
    gcdata = 0x1065b18 <func.*+254> "\002",
    str = 2790,
    ptrToThis = 9664
  },
  pkgpath = {
    bytes = 0x105500a <type.*+298> ""
  },
  mhdr = []runtime.imethod = {{
      name = 8,
      ityp = 15552
    }, {
      name = 11,
--Type <RET> for more, q to quit, c to continue without paging--

(gdb) ptype t
type = struct runtime.iface {
    runtime.itab *tab;
    void *data;
}
(gdb) p t
$2 = {tab = 0x1076b60 <N,main.Ner>, data = 0xc00003c748}

(gdb) ptype t.tab._type
type = struct runtime._type {
    uintptr size;
    uintptr ptrdata;
    uint32 hash;
    runtime.tflag tflag;
    uint8 align;
    uint8 fieldAlign;
    uint8 kind;
    func(unsafe.Pointer, unsafe.Pointer) bool equal;
    uint8 *gcdata;
--Type <RET> for more, q to quit, c to continue without paging--

Follow-up todo

Combining the structure of iface and eface to analyze a series of problems such as interface judgment

Reference

gdb-debugger-with-go