/*
 * Benchmark harness for vlibc (musts/BENCHMARKING.md).
 *
 * Every vlibc component is benchmarked against the software it replaces.
 * This stub times vlibc_version() and is the skeleton that per-component
 * benchmarks build on. Reconfigure with --with-libc=musl or --with-libc=glibc
 * to link the same harness against a reference libc for comparison.
 *
 * This TU is deliberately a HOST-headers-only translation unit: it includes
 * no vlibc header, because vlibc's self-contained
 * <stdarg.h>/<stddef.h>/<limits.h>/<float.h> shadow GCC's internal headers
 * and mixing them with the system <stdio.h>/<time.h> hard-errors. The
 * function under test is reached through the adapter TU
 * bench_vlibc_under.c, which is compiled with vlibc's headers and exposes
 * the call through its own declaration here.
 */
#ifdef HAVE_CONFIG_H
#include <config.h>
#endif

#include <stdio.h>
#include <time.h>

/* Adapter entry (bench_vlibc_under.c); declared here rather than including
 * <vlibc.h>, which this host-header TU must not do. The adapter also drops
 * vlibc_version()'s __attribute__((const)), so the timed loop really
 * executes the call. */
const char *
bench_vlibc_version(void);

#define ITERATIONS 100000000ULL

int
main(void)
{
    volatile const char *version = NULL;
    struct timespec start;
    struct timespec end;
    double whole;
    double frac;
    double seconds;

    if (clock_gettime(CLOCK_MONOTONIC, &start) != 0)
    {
        return 1;
    }

    for (unsigned long long i = 0; i < ITERATIONS; i++)
    {
        version = bench_vlibc_version();
    }

    if (clock_gettime(CLOCK_MONOTONIC, &end) != 0)
    {
        return 1;
    }

    whole = (double)(end.tv_sec - start.tv_sec);
    frac = (double)(end.tv_nsec - start.tv_nsec) / 1000000000.0;
    seconds = whole + frac;

    printf("vlibc_version() x %llu: %.3f s (%.2f ns/call), version=%s\n", ITERATIONS, seconds,
           seconds * 1000000000.0 / ITERATIONS, (const char *)version);

    /*
     * Explicit flush: this harness is a host program, but its DT_NEEDED order
     * puts libvlibc.so before libc.so.6, so the exit() that runs at process
     * end is vlibc's — which does not flush stdio yet (that hook lands with
     * the stdio todo). Without the flush the buffered result above is lost.
     */
    fflush(stdout);

    return 0;
}