By adding the link flags `-s -w` we can reduce the Vault binary size
from 204 MB to 167 MB (about 18% reduction in size).
This removes the DWARF section of the binary.
i.e., before:
```
$ objdump --section-headers vault-debug
vault-debug: file format mach-o arm64
Sections:
Idx Name Size VMA Type
0 __text 03a00340 0000000100001000 TEXT
1 __symbol_stub1 00000618 0000000103a01340 TEXT
2 __rodata 00c18088 0000000103a01960 DATA
3 __rodata 015aee18 000000010461c000 DATA
4 __typelink 0004616c 0000000105bcae20 DATA
5 __itablink 0000eb68 0000000105c10fa0 DATA
6 __gosymtab 00000000 0000000105c1fb08 DATA
7 __gopclntab 02a5b8e0 0000000105c1fb20 DATA
8 __go_buildinfo 00008c10 000000010867c000 DATA
9 __nl_symbol_ptr 00000410 0000000108684c10 DATA
10 __noptrdata 000fed00 0000000108685020 DATA
11 __data 0004e1f0 0000000108783d20 DATA
12 __bss 00052520 00000001087d1f20 BSS
13 __noptrbss 000151b0 0000000108824440 BSS
14 __zdebug_abbrev 00000129 000000010883c000 DATA, DEBUG
15 __zdebug_line 00651374 000000010883c129 DATA, DEBUG
16 __zdebug_frame 001e1de9 0000000108e8d49d DATA, DEBUG
17 __debug_gdb_scri 00000043 000000010906f286 DATA, DEBUG
18 __zdebug_info 00de2c09 000000010906f2c9 DATA, DEBUG
19 __zdebug_loc 00a619ea 0000000109e51ed2 DATA, DEBUG
20 __zdebug_ranges 001e94a6 000000010a8b38bc DATA, DEBUG
```
And after:
```
$ objdump --section-headers vault-no-debug
vault-no-debug: file format mach-o arm64
Sections:
Idx Name Size VMA Type
0 __text 03a00340 0000000100001000 TEXT
1 __symbol_stub1 00000618 0000000103a01340 TEXT
2 __rodata 00c18088 0000000103a01960 DATA
3 __rodata 015aee18 000000010461c000 DATA
4 __typelink 0004616c 0000000105bcae20 DATA
5 __itablink 0000eb68 0000000105c10fa0 DATA
6 __gosymtab 00000000 0000000105c1fb08 DATA
7 __gopclntab 02a5b8e0 0000000105c1fb20 DATA
8 __go_buildinfo 00008c20 000000010867c000 DATA
9 __nl_symbol_ptr 00000410 0000000108684c20 DATA
10 __noptrdata 000fed00 0000000108685040 DATA
11 __data 0004e1f0 0000000108783d40 DATA
12 __bss 00052520 00000001087d1f40 BSS
13 __noptrbss 000151b0 0000000108824460 BSS
```
The only side effect I have been able to find is that it is no longer
possible to use [delve](https://github.com/go-delve/delve) to run the
Vault binary.
Note, however, that running delve and other debuggers requires access
to the full source code, which isn't provided for the Enterprise, HSM,
etc. binaries, so it isn't possible to debug those anyway outside of
people who have the full source.
* panic traces
* `vault debug`
* error messages
* Despite what the documentation says, these flags do *not* delete the
function symbol table (so it is not the same as having a `strip`ped
binary).
It contains mappings between the compiled binary and functions,
paramters, and variables in the source code.
Using `llvm-dwarfdump`, it looks like:
```
0x011a6d85: DW_TAG_subprogram
DW_AT_name ("github.com/hashicorp/vault/api.(*replicationStateStore).recordState")
DW_AT_low_pc (0x0000000000a99300)
DW_AT_high_pc (0x0000000000a99419)
DW_AT_frame_base (DW_OP_call_frame_cfa)
DW_AT_decl_file ("/home/swenson/vault/api/client.go")
DW_AT_external (0x01)
0x011a6de1: DW_TAG_formal_parameter
DW_AT_name ("w")
DW_AT_variable_parameter (0x00)
DW_AT_decl_line (1735)
DW_AT_type (0x00000000001e834a "github.com/hashicorp/vault/api.replicationStateStore *")
DW_AT_location (0x009e832a:
[0x0000000000a99300, 0x0000000000a9933a): DW_OP_reg0 RAX
[0x0000000000a9933a, 0x0000000000a99419): DW_OP_call_frame_cfa)
0x011a6def: DW_TAG_formal_parameter
DW_AT_name ("resp")
DW_AT_variable_parameter (0x00)
DW_AT_decl_line (1735)
DW_AT_type (0x00000000001e82a2 "github.com/hashicorp/vault/api.Response *")
DW_AT_location (0x009e8370:
[0x0000000000a99300, 0x0000000000a9933a): DW_OP_reg3 RBX
[0x0000000000a9933a, 0x0000000000a99419): DW_OP_fbreg +8)
0x011a6e00: DW_TAG_variable
DW_AT_name ("newState")
DW_AT_decl_line (1738)
DW_AT_type (0x0000000000119f32 "string")
DW_AT_location (0x009e83b7:
[0x0000000000a99385, 0x0000000000a99385): DW_OP_reg0 RAX, DW_OP_piece 0x8, DW_OP_piece 0x8
[0x0000000000a99385, 0x0000000000a993a4): DW_OP_reg0 RAX, DW_OP_piece 0x8, DW_OP_reg3 RBX, DW_OP_piece 0x8
[0x0000000000a993a4, 0x0000000000a993a7): DW_OP_piece 0x8, DW_OP_reg3 RBX, DW_OP_piece 0x8)
```
This says that the particular binary section is the function
`github.com/hashicorp/vault/api.(*replicationStateStore).recordState`,
from the file `/home/swenson/vault/api/client.go`, containing
the `w` parameter on line 1735 mapped to certain registers and memory,
the `resp` paramter on line 1735 mapped to certain reigsters and memory,
and the `newState` variable on line 1738, mapped to certain registers,
and memory.
It's really only useful for a debugger.
Anyone running the code in a debugger will need full access the source
code anyway, so presumably they will be able to run `make dev` and build
the version with the DWARF sections intact, and then run their debugger.
Christopher Swenson