vlibc/tests/test_strerror.c

/*
 * vlibc — strerror/strerror_r test (todo 2).
 *
 * Exercises the public <errno.h> end to end:
 *
 *   1. strerror(0) is "Success"; known values return the exact message and
 *      are non-NULL and distinct; aliases (EWOULDBLOCK/EDEADLOCK) resolve to
 *      their canonical entries; the last table value (EHWPOISON) is covered.
 *   2. Unknown errno values never return NULL and never crash: 9999 and the
 *      ABI-gap value 41 format as "Unknown error <N>", negatives too.
 *   3. strerror_r (XSI): returns 0 and fills buf with the right text; an
 *      unknown value still returns 0 with "Unknown error <N>"; truncation
 *      into a tiny buf stays NUL-terminated; buflen 0 writes nothing; a NULL
 *      buf with buflen > 0 returns EINVAL.
 *
 * The test deliberately never touches errno itself: under the host libc the
 * TCB slot our errno macro addresses is glibc's private TLS state, and
 * writing it would corrupt the host (see tests/syscall_test.c). All coverage
 * here is through the errnum parameters.
 *
 * All diagnostics go through raw SYS_write (no stdio): under -Iinclude the
 * vlibc public headers shadow GCC's internal ones, so mixing in a host
 * <stdio.h> breaks compilation (glibc's stdio.h pulls in our minimal
 * <stdarg.h>, which lacks __gnuc_va_list). <string.h> below is vlibc's own
 * header, which is safe.
 *
 * Not part of the library proper; compiled manually for this todo (the
 * tests/ + make check wiring is owned by a later todo).
 */

#include <errno.h>
#include <string.h>

#include "../src/internal/syscall.h"

static int failures;

/* Write a NUL-terminated string to fd via the raw syscall layer. */
static void
say(int fd, const char *s)
{
    long n = 0;

    while (s[n] != '\0')
    {
        n++;
    }
    __syscall3(SYS_write, fd, (long)s, n);
}

static void
check(int cond, const char *what)
{
    if (!cond)
    {
        say(2, "FAIL: ");
        say(2, what);
        say(2, "\n");
        failures++;
    }
}

/*
 * Failure scenario (-f): an unknown errno must yield "Unknown error 9999",
 * non-NULL, without crashing. Prints the observed string; exits 0 only when
 * the failure behaved exactly as specified.
 */
static int
failure_scenario(void)
{
    const char *s = strerror(9999);

    if (s == NULL)
    {
        say(1, "strerror(9999)=NULL\n");
        return 1;
    }
    say(1, "strerror(9999)=");
    say(1, s);
    say(1, "\n");
    return strcmp(s, "Unknown error 9999") == 0 ? 0 : 1;
}

int
main(int argc, char **argv)
{
    const char *a;
    const char *b;
    char buf[64];
    char tiny[8];
    char untouched[4];
    int r;

    if (argc == 2 && argv[1][0] == '-' && argv[1][1] == 'f')
    {
        return failure_scenario();
    }

    /* 1. Known values: exact text, non-NULL, distinct. */
    check(strcmp(strerror(0), "Success") == 0, "strerror(0) == \"Success\"");
    check(strcmp(strerror(2), "No such file or directory") == 0,
          "strerror(2) == \"No such file or directory\"");
    check(strcmp(strerror(EINVAL), "Invalid argument") == 0,
          "strerror(EINVAL) == \"Invalid argument\"");
    check(strcmp(strerror(EPERM), "Operation not permitted") == 0,
          "strerror(EPERM) == \"Operation not permitted\"");

    a = strerror(EINVAL);
    b = strerror(EPERM);
    check(a != NULL && b != NULL, "known values non-NULL");
    check(a != b, "known values distinct");

    /* Aliases resolve to their canonical entries. */
    check(strerror(EWOULDBLOCK) == strerror(EAGAIN), "EWOULDBLOCK == EAGAIN");
    check(strerror(EDEADLOCK) == strerror(EDEADLK), "EDEADLOCK == EDEADLK");

    /* Table ends: last defined value and ABI gap values. */
    check(strerror(EHWPOISON) != NULL, "EHWPOISON (last value) non-NULL");
    check(strcmp(strerror(41), "Unknown error 41") == 0, "ABI gap 41 unknown");
    check(strcmp(strerror(58), "Unknown error 58") == 0, "ABI gap 58 unknown");

    /* 2. Unknown values: never NULL, never crash, formatted. */
    a = strerror(9999);
    check(a != NULL, "strerror(9999) non-NULL");
    check(strcmp(a, "Unknown error 9999") == 0, "strerror(9999) text");

    a = strerror(-7);
    check(a != NULL, "strerror(-7) non-NULL");
    check(strcmp(a, "Unknown error -7") == 0, "strerror(-7) text");

    /* 3. strerror_r: XSI int return, exact fill. */
    r = strerror_r(EDOM, buf, sizeof buf);
    check(r == 0, "strerror_r(EDOM) returns 0");
    check(strcmp(buf, "Numerical argument out of domain") == 0, "strerror_r(EDOM) fills buf");

    /* Unknown errno still succeeds and formats into buf (XSI). */
    r = strerror_r(9999, buf, sizeof buf);
    check(r == 0, "strerror_r(9999) returns 0 (XSI)");
    check(strcmp(buf, "Unknown error 9999") == 0, "strerror_r(9999) text");

    /* Truncation into a tiny buf stays NUL-terminated. */
    r = strerror_r(ENAMETOOLONG, tiny, sizeof tiny);
    check(r == 0, "strerror_r(ENAMETOOLONG, tiny) returns 0");
    check(tiny[sizeof tiny - 1] == '\0', "tiny buf NUL-terminated");
    check(strcmp(tiny, "File na") == 0, "tiny buf truncated prefix");

    /* buflen 0: nothing written, still success. */
    untouched[0] = 'X';
    untouched[1] = 'X';
    untouched[2] = 'X';
    untouched[3] = '\0';
    r = strerror_r(EDOM, untouched, 0);
    check(r == 0, "strerror_r(EDOM, buf, 0) returns 0");
    check(untouched[0] == 'X', "buflen 0 writes nothing");

    /* NULL buf with buflen > 0: EINVAL. */
    r = strerror_r(EDOM, NULL, 16);
    check(r == EINVAL, "strerror_r(NULL buf) returns EINVAL");

    if (failures > 0)
    {
        say(2, "FAILED\n");
    }
    else
    {
        say(1, "strerror ok\n");
    }
    return failures == 0 ? 0 : 1;
}