Issues with linker variable values in Zig

gistfile1.txt

test.zig

// .data related linker variables
extern const _data_begin: u32;
extern const _data_end: u32;
extern var _d: u32;

// .bss related linker variables
extern var _bss_begin: u32;
extern const _bss_end: u32;
extern var _b: u32;

var bss_var: u16 = 0;
var data_var: u16 = 1234;
const rodata_var: u16 = 4567;

nakedcc fn _start() void {
    var db = &_data_begin;
    var de = &_data_end;
    var d_size = @ptrToInt(de) - @ptrToInt(db);
    var bb = &_bss_begin;
    var be = &_bss_end;
    var b_size = @ptrToInt(be) - @ptrToInt(bb);

    bss_var = 1;
    data_var = 2;
    var x = rodata_var;
    
    
build.zig

const builtin = @import("builtin");
const Builder = @import("std").build.Builder;

pub fn build(b: *Builder) void {
    const mode = b.standardReleaseOptions();
    const exe = b.addExecutable("SAM3X8E", "test.zig");
    exe.setTarget(builtin.Arch.armv7m, builtin.Os.freestanding, builtin.Environ.eabi);
    exe.setBuildMode(mode);
    exe.setLinkerScriptPath("build.ld");

    const run_step = b.step("run", "Run the app");
    const run_cmd = b.addCommand(".", b.env_map, [][]const u8{exe.getOutputPath()});
    run_step.dependOn(&run_cmd.step);
    run_cmd.step.dependOn(&exe.step);

    b.default_step.dependOn(&exe.step);
    b.installArtifact(exe);
}



build.ld

MEMORY
{
    sram0 (!rx)   : ORIGIN = 0x20000000, LENGTH = 64K
    sram1 (!rx)   : ORIGIN = 0x20080000, LENGTH = 32K
    nfcsram (!rx) : ORIGIN = 0x20100000, LENGTH = 4224

    flash0 (rx) : ORIGIN = 0x00080000, LENGTH = 256K
    flash1 (rx) : ORIGIN = 0x000c0000, LENGTH = 256K

    pioa (rw) : ORIGIN = 0x400e0e00, LENGTH = 328
    piob (rw) : ORIGIN = 0x400e1000, LENGTH = 328
    pioc (rw) : ORIGIN = 0x400e1200, LENGTH = 328
    piod (rw) : ORIGIN = 0x400e1400, LENGTH = 328
}

SECTIONS
{
    .text :
    {
        KEEP(*(.vector));
        . = ALIGN(4);
        *(.text);
    }>flash0
    . = ALIGN(4);
    _d = .;
    .data : AT(_d)
    {
        . = ALIGN(4);
        _data_begin = .;
        *(.data);
        . = ALIGN(4);
        _data_end = .;
    }>sram0
    _b = .;
    .bss (NOLOAD) :
    {
        . = ALIGN(4);
        _bss_begin = .;
        *(.bss);
        . = ALIGN(4);
        _bss_end = .;
    }>sram0
    .rodata :
    {
        . = ALIGN(4);
        *(.rodata);
    }>flash0
    .data.rel.ro :
    {
        . = ALIGN(4);
        *(.data.rel.ro);
    }>flash0
    .got :
    {
        . = ALIGN(4);
        *(.got);
    }>flash0
    .ARM :
    {
        . = ALIGN(4);
        *(.ARM.exidx);
    }>flash0

    .pioa (NOLOAD) :
    {
        *(.pioa);
    }>pioa
    .piob (NOLOAD) :
    {
        *(.piob);
    }>piob
    .pioc (NOLOAD) :
    {
        *(.pioc);
    }>pioc
    .piod (NOLOAD) :
    {
        *(.piod);
    }>piod
}