Description
Zig Version
0.14.0
Steps to Reproduce and Observed Behavior
Debug info for some struct in Zig standard library, built on Linux:
% cat b.zig
const std = @import("std");
pub fn main() !void {}
% zig build-exe b.zig
% llvm-dwarfdump-18 b | grep -A4 -B18 -m1 DW_AT_lower_bound
0x000000dc: DW_TAG_structure_type
DW_AT_name ("Target.Cpu.Feature.Set")
DW_AT_byte_size (0x28)
DW_AT_alignment (8)
0x000000e3: DW_TAG_member
DW_AT_name ("ints")
DW_AT_type (0x000000ef "usize[5]")
DW_AT_alignment (8)
DW_AT_data_member_location (0x00)
0x000000ee: NULL
0x000000ef: DW_TAG_array_type
DW_AT_type (0x000000fd "usize")
0x000000f4: DW_TAG_subrange_type
DW_AT_type (0x00000104 "__ARRAY_SIZE_TYPE__")
DW_AT_lower_bound (-3539)
DW_AT_count (0x05)
0x000000fc: NULL
This DW_AT_lower_bound seems to say that the indexing of array Target.Cpu.Feature.Set.ints (presumably in zig/lib/std/Target.zig in the standard library) starts at -3539. It looks like a regular array, pretty sure its indexes are 0-based rather than -3539-based.
Reproduces with -fno-llvm -fno-lld as well, but the value is 1759 instead of -3539.
(I think I also reproduced it with an array in my own program, where I confirmed with debugger that indexing starts at zero, i.e. no weird advanced optimization happened where the index has to be adjusted or something. But the repro was inconsistent and stopped working at some point, and I gave up. Either it's nondeterministic or I've gone mad from staring at dwarfdump outputs for too long.)
Expected Behavior
No DW_AT_lower_bound attribute.