`-gdwarf64` does not produce object with 64bit DWARF debug info

Zig Version

0.12.0-dev.3475+71d878ba5

Steps to Reproduce and Observed Behavior

Run the following build command with a minimal zig file

zig build-obj -gdwarf64 -O Debug -target x86_64-linux example.zig

Example.zig:

const std = @import("std");

pub fn main() void {
    std.debug.print("example zig\n", .{});
}

Then use objdump to check DWARF info:

objdump --dwarf=info example.o

example.o:     file format elf64-x86-64

Contents of the .debug_info section:

  Compilation Unit @ offset 0:
   Length:        0x25f5d (32-bit)
   Version:       4
   Abbrev Offset: 0
   Pointer Size:  8
 <0><b>: Abbrev Number: 1 (DW_TAG_compile_unit)
    <c>   DW_AT_producer    : (indirect string, offset: 0x1887b): zig 0.12.0
    <10>   DW_AT_language    : 12       (ANSI C99)
    <12>   DW_AT_name        : (indirect string, offset: 0x6753): example
...

It shows 32-bit instead of 64-bit, as seen from another object file built with GCC with -g -gdwarf64:

gcc -g -gdwarf64 -c hello.c
objdump --dwarf=info hello.o

hello.o:     file format elf64-x86-64

Contents of the .debug_info section:

  Compilation Unit @ offset 0:
   Length:        0xff (64-bit)
   Version:       5
   Unit Type:     DW_UT_compile (1)
   Abbrev Offset: 0
   Pointer Size:  8
...

Expected Behavior

-gdwarf32 and -gdwarf64 should produce 32-bit and 64-bit DWARF debug info accordingly.

My speculation on this:

Those two options were added in https://github.com/ziglang/zig/commit/d026202a26e56e7e2ea20ca49509fdcf8b937020 , at that time there were no CreateModule struct, and those options get passed directly to Compilation.create.

But now it is stored in create_module.opts, which is resolved into create_module.resolved_options at: https://github.com/ziglang/zig/blob/a2df84d0ffe3b7bce96f55a5d7063630aac75116/src/Compilation/Config.zig#L424-L435

The code above didn't consider options.debug_format to generate create_module.resolved_options, so the options were not in effect.

ziglang / zig