unwanted struct initialization

getr.zig

// on macOS: zig build-exe getr.zig --library c --libc-include-dir /usr/local/Cellar/musl-cross/0.9.7_1/libexec/x86_64-linux-musl/include
const std = @import("std");
const c = @cImport({
   @cInclude("sys/resource.h");
   @cInclude("spawn.h");
});
const warn = std.debug.warn;

const report_time =
   \\User time      : {} s, {} us
   \\System time    : {} s, {} us
   \\Time           : {} ms ({} ms/per)
   \\
;
const report_rss =
   \\Max RSS        : {} kB
   \\Shared RSS     : {} kB
   \\Unshared Data  : {}
   \\Unshared Stack : {}
   \\
;
const report =
   \\Page reclaims  : {}
   \\Page faults    : {}
   \\Swaps          : {}
   \\Block inputs   : {}
   \\Block outputs  : {}
   \\Sigs received  : {}
   \\vol ctx switches   : {}
   \\invol ctx switches : {}
   \\
;

pub fn main() void {
   const count = 2;
   var usage: c.struct_rusage = undefined;
   if (c.getrusage(c.RUSAGE_SELF, @ptrCast(?[*]c.struct_rusage, &usage)) == 0) {
      const time = @divTrunc((usage.ru_utime.tv_usec + usage.ru_stime.tv_usec), 1000)
         + @divTrunc((usage.ru_utime.tv_sec + usage.ru_stime.tv_sec), 1000);
      const ptime = (@intToFloat(f64, usage.ru_utime.tv_usec + usage.ru_stime.tv_usec)/1000.0
         + (@intToFloat(f64, usage.ru_utime.tv_sec + usage.ru_stime.tv_sec)*1000.0))/@intToFloat(f64, count);
      warn(report_time,
         usage.ru_utime.tv_sec, usage.ru_utime.tv_usec,
         usage.ru_stime.tv_sec, usage.ru_stime.tv_usec,
         time, ptime);
      warn(report_rss,
         usage.ru_maxrss,
         usage.ru_ixrss,
         usage.ru_idrss,
         usage.ru_idrss);
      warn(report,
         usage.ru_minflt,
         usage.ru_majflt,
         usage.ru_nswap,
         usage.ru_inblock,
         usage.ru_oublock,
         usage.ru_nsignals,
         usage.ru_nvcsw,
         usage.ru_nivcsw);
   }
}