libakstdlib/tests/test_stream.c

/*
 * Stream wrappers: aksl_fopen / aksl_fread / aksl_fwrite / aksl_fclose.
 *
 * TODO.md section 1.2, now complete. The happy paths, the round trip, every
 * NULL guard, both stream-error statuses, the transferred-member count that
 * aksl_fread and aksl_fwrite report through nmemb_out, and the three cases that
 * needed a hostile file to produce: a mode-denied path (EACCES), a full device
 * (/dev/full) for the short write, and a stream whose buffered flush fails at
 * fclose time.
 *
 * The /dev/full tests are skipped where the device is absent -- it is a Linux
 * thing -- rather than failing, and say so on stderr so a skip cannot be
 * mistaken for a pass.
 *
 * Temp files come from aksl_temp_file() and are unlinked by the test that made
 * them, so a failing test leaves nothing behind but the file it was mid-way
 * through.
 */

#include "aksl_capture.h"

#include <errno.h>
#include <sys/stat.h>

static int test_fopen_writes_stream_pointer(void)
{
    char path[AKSL_TMP_MAX];
    FILE *fp = NULL;

    AKSL_CHECK(aksl_temp_file(path, sizeof(path)) == 0);
    AKSL_CHECK_OK(aksl_fopen(path, "w", &fp));
    AKSL_CHECK(fp != NULL);
    AKSL_CHECK_OK(aksl_fclose(fp));
    AKSL_CHECK(unlink(path) == 0);
    return 0;
}

static int test_fopen_reports_missing_path(void)
{
    FILE *fp = NULL;

    /* The pathname belongs in the message; the status is the errno fopen saw. */
    AKSL_CHECK_STATUS_MSG_CONTAINS(
	aksl_fopen("/nonexistent/aksl/stream", "r", &fp),
	ENOENT, "/nonexistent/aksl/stream");
    /* *fp is cleared before the call, so a failed open cannot leave garbage. */
    AKSL_CHECK(fp == NULL);
    return 0;
}

/*
 * A file the caller cannot open for reading is EACCES rather than ENOENT.
 * Skipped under a user who bypasses the permission bits -- root, or anything
 * holding CAP_DAC_OVERRIDE -- where chmod 000 simply does not deny anything.
 */
static int test_fopen_reports_permission_denied(void)
{
    char path[AKSL_TMP_MAX];
    FILE *fp = NULL;

    AKSL_CHECK(aksl_temp_file(path, sizeof(path)) == 0);
    AKSL_CHECK(chmod(path, 0000) == 0);

    if ( geteuid() == 0 ) {
	fprintf(stderr, "     (skipped: running as root, chmod 000 denies nothing)\n");
	AKSL_CHECK(unlink(path) == 0);
	return 0;
    }

    AKSL_CHECK_STATUS_MSG_CONTAINS(aksl_fopen(path, "r", &fp), EACCES, path);
    AKSL_CHECK(unlink(path) == 0);
    return 0;
}

static int test_fopen_rejects_null_arguments(void)
{
    char path[AKSL_TMP_MAX];
    FILE *fp = NULL;

    AKSL_CHECK(aksl_temp_file(path, sizeof(path)) == 0);

    AKSL_CHECK_STATUS_MSG_CONTAINS(aksl_fopen(path, "r", NULL),
				   AKERR_NULLPOINTER, "fp=");
    /* TODO.md 2.2.2: both of these used to go straight through to fopen(3). */
    AKSL_CHECK_STATUS_MSG_CONTAINS(aksl_fopen(NULL, "r", &fp),
				   AKERR_NULLPOINTER, "pathname=");
    AKSL_CHECK_STATUS_MSG_CONTAINS(aksl_fopen(path, NULL, &fp),
				   AKERR_NULLPOINTER, "mode=");
    AKSL_CHECK(unlink(path) == 0);
    return 0;
}

/* fopen -> fwrite -> fclose -> fopen -> fread -> compare, all through the wrappers. */
static int test_write_read_round_trip(void)
{
    char path[AKSL_TMP_MAX];
    char payload[] = "libakstdlib round trip";
    char readback[sizeof(payload)];
    size_t moved = 0;
    FILE *fp = NULL;

    AKSL_CHECK(aksl_temp_file(path, sizeof(path)) == 0);

    AKSL_CHECK_OK(aksl_fopen(path, "w", &fp));
    AKSL_CHECK_OK(aksl_fwrite(payload, 1, sizeof(payload), fp, &moved));
    AKSL_CHECK(moved == sizeof(payload));
    AKSL_CHECK_OK(aksl_fclose(fp));

    fp = NULL;
    moved = 0;
    memset(readback, 0x00, sizeof(readback));
    AKSL_CHECK_OK(aksl_fopen(path, "r", &fp));
    AKSL_CHECK_OK(aksl_fread(readback, 1, sizeof(readback), fp, &moved));
    AKSL_CHECK(moved == sizeof(readback));
    AKSL_CHECK_OK(aksl_fclose(fp));

    AKSL_CHECK(memcmp(payload, readback, sizeof(payload)) == 0);
    AKSL_CHECK(unlink(path) == 0);
    return 0;
}

/*
 * Asking for more members than the file holds sets feof, which is AKERR_EOF --
 * and nmemb_out says how many did arrive, which is the entire reason for
 * distinguishing EOF from an error rather than reporting both as AKERR_IO.
 */
static int test_fread_short_read_is_eof_and_reports_the_count(void)
{
    char path[AKSL_TMP_MAX];
    char buf[32];
    size_t moved = 0;
    FILE *fp = NULL;

    AKSL_CHECK(aksl_temp_file(path, sizeof(path)) == 0);

    AKSL_CHECK_OK(aksl_fopen(path, "w", &fp));
    AKSL_CHECK_OK(aksl_fwrite("abcd", 1, 4, fp, &moved));
    AKSL_CHECK(moved == 4);
    AKSL_CHECK_OK(aksl_fclose(fp));

    fp = NULL;
    moved = 99;
    memset(buf, 0x00, sizeof(buf));
    AKSL_CHECK_OK(aksl_fopen(path, "r", &fp));
    AKSL_CHECK_STATUS_MSG_CONTAINS(aksl_fread(buf, 1, sizeof(buf), fp, &moved),
				   AKERR_EOF, "EOF");
    /* TODO.md 2.2.3: this is what the caller could not previously find out. */
    AKSL_CHECK(moved == 4);
    AKSL_CHECK_OK(aksl_fclose(fp));

    AKSL_CHECK(memcmp(buf, "abcd", 4) == 0);
    AKSL_CHECK(unlink(path) == 0);
    return 0;
}

/*
 * A stream opened "w" has no read permission, so fread sets the error indicator
 * rather than the EOF one -- and the status is the errno the C library actually
 * saw, EBADF, rather than a flat AKERR_IO.
 *
 * That is a change from the old wrapper, which read ferror() and reported
 * AKERR_IO without ever consulting errno. Routing it through AKSL_ERRNO_OR
 * (TODO.md 2.2.1) keeps AKERR_IO as the fallback for the case where the stream
 * is in error and errno says nothing, and hands back the real reason otherwise.
 */
static int test_fread_from_write_only_stream_reports_errno(void)
{
    char path[AKSL_TMP_MAX];
    char buf[4];
    size_t moved = 99;
    FILE *fp = NULL;

    AKSL_CHECK(aksl_temp_file(path, sizeof(path)) == 0);
    AKSL_CHECK_OK(aksl_fopen(path, "w", &fp));
    memset(buf, 0x00, sizeof(buf));
    AKSL_CHECK_STATUS_MSG_CONTAINS(aksl_fread(buf, 1, sizeof(buf), fp, &moved),
				   EBADF, "of 4 members");
    AKSL_CHECK(moved == 0);
    AKSL_CHECK_OK(aksl_fclose(fp));
    AKSL_CHECK(unlink(path) == 0);
    return 0;
}

static int test_fread_rejects_null_arguments(void)
{
    char path[AKSL_TMP_MAX];
    char buf[4];
    size_t moved = 0;
    FILE *fp = NULL;

    memset(buf, 0x00, sizeof(buf));
    AKSL_CHECK(aksl_temp_file(path, sizeof(path)) == 0);
    AKSL_CHECK_OK(aksl_fopen(path, "r", &fp));

    AKSL_CHECK_STATUS_MSG_CONTAINS(aksl_fread(buf, 1, sizeof(buf), NULL, &moved),
				   AKERR_NULLPOINTER, "fp=");
    /* TODO.md 2.2.3: ptr was never checked in either direction. */
    AKSL_CHECK_STATUS_MSG_CONTAINS(aksl_fread(NULL, 1, sizeof(buf), fp, &moved),
				   AKERR_NULLPOINTER, "ptr=");
    AKSL_CHECK_STATUS_MSG_CONTAINS(aksl_fread(buf, 1, sizeof(buf), fp, NULL),
				   AKERR_NULLPOINTER, "nmemb_out=");

    AKSL_CHECK_OK(aksl_fclose(fp));
    AKSL_CHECK(unlink(path) == 0);
    return 0;
}

/* Mirror image of the fread case: a "r" stream cannot be written to. */
static int test_fwrite_to_read_only_stream_reports_errno(void)
{
    char path[AKSL_TMP_MAX];
    size_t moved = 99;
    FILE *fp = NULL;

    AKSL_CHECK(aksl_temp_file(path, sizeof(path)) == 0);
    AKSL_CHECK_OK(aksl_fopen(path, "r", &fp));
    AKSL_CHECK_STATUS_MSG_CONTAINS(aksl_fwrite("xy", 1, 2, fp, &moved),
				   EBADF, "wrote 0 of 2 members");
    AKSL_CHECK(moved == 0);
    AKSL_CHECK_OK(aksl_fclose(fp));
    AKSL_CHECK(unlink(path) == 0);
    return 0;
}

static int test_fwrite_rejects_null_arguments(void)
{
    size_t moved = 0;

    AKSL_CHECK_STATUS_MSG_CONTAINS(aksl_fwrite("xy", 1, 2, NULL, &moved),
				   AKERR_NULLPOINTER, "fp=");
    AKSL_CHECK_STATUS_MSG_CONTAINS(aksl_fwrite(NULL, 1, 2, stdout, &moved),
				   AKERR_NULLPOINTER, "ptr=");
    AKSL_CHECK_STATUS_MSG_CONTAINS(aksl_fwrite("xy", 1, 2, stdout, NULL),
				   AKERR_NULLPOINTER, "nmemb_out=");
    return 0;
}

/*
 * /dev/full accepts an open for writing and then fails every write with ENOSPC.
 * It is the only convenient way to reach a genuinely short write on a stream
 * that is otherwise perfectly healthy.
 */
static int test_fwrite_to_full_device_reports_enospc(void)
{
    char payload[8192];
    size_t moved = 99;
    FILE *fp = NULL;

    if ( access("/dev/full", W_OK) != 0 ) {
	fprintf(stderr, "     (skipped: no writable /dev/full on this platform)\n");
	return 0;
    }

    memset(payload, 'x', sizeof(payload));
    AKSL_CHECK_OK(aksl_fopen("/dev/full", "w", &fp));
    /*
     * Larger than any plausible stdio buffer, so the write reaches the device
     * inside fwrite rather than being deferred to fclose -- the deferred case is
     * the next test.
     */
    AKSL_CHECK_STATUS(aksl_fwrite(payload, 1, sizeof(payload), fp, &moved), ENOSPC);
    AKSL_CHECK(moved < sizeof(payload));
    /*
     * fclose succeeds here, and that is not a contradiction: the write already
     * reached the device and failed, so by close time there is nothing left
     * buffered to fail on. The deferred case -- where the write fits in the
     * stdio buffer and only fclose finds out -- is the next test. Take the
     * context however it comes back rather than asserting either way, since
     * whether the error indicator survives to fclose is a stdio implementation
     * detail and not part of this library's contract.
     */
    (void)aksl_take(aksl_fclose(fp));
    return 0;
}

/*
 * The write that fits in the stdio buffer succeeds, and the failure surfaces
 * only when fclose flushes it. A caller who checks fwrite and ignores fclose
 * loses the data silently, which is why aksl_fclose reports errno rather than
 * just a non-zero return.
 */
static int test_fclose_surfaces_a_failed_flush(void)
{
    size_t moved = 0;
    FILE *fp = NULL;

    if ( access("/dev/full", W_OK) != 0 ) {
	fprintf(stderr, "     (skipped: no writable /dev/full on this platform)\n");
	return 0;
    }

    AKSL_CHECK_OK(aksl_fopen("/dev/full", "w", &fp));
    AKSL_CHECK_OK(aksl_fwrite("small", 1, 5, fp, &moved));
    AKSL_CHECK(moved == 5);
    AKSL_CHECK_STATUS_MSG_CONTAINS(aksl_fclose(fp), ENOSPC, "buffered data is lost");
    return 0;
}

static int test_fclose_rejects_null_stream(void)
{
    AKSL_CHECK_STATUS_MSG_CONTAINS(aksl_fclose(NULL),
				   AKERR_NULLPOINTER, "NULL");
    return 0;
}

int main(void)
{
    int failures = 0;

    akerr_init();

    AKSL_RUN(failures, test_fopen_writes_stream_pointer);
    AKSL_RUN(failures, test_fopen_reports_missing_path);
    AKSL_RUN(failures, test_fopen_reports_permission_denied);
    AKSL_RUN(failures, test_fopen_rejects_null_arguments);

    AKSL_RUN(failures, test_write_read_round_trip);
    AKSL_RUN(failures, test_fread_short_read_is_eof_and_reports_the_count);
    AKSL_RUN(failures, test_fread_from_write_only_stream_reports_errno);
    AKSL_RUN(failures, test_fread_rejects_null_arguments);

    AKSL_RUN(failures, test_fwrite_to_read_only_stream_reports_errno);
    AKSL_RUN(failures, test_fwrite_rejects_null_arguments);
    AKSL_RUN(failures, test_fwrite_to_full_device_reports_enospc);

    AKSL_RUN(failures, test_fclose_surfaces_a_failed_flush);
    AKSL_RUN(failures, test_fclose_rejects_null_stream);

    AKSL_REPORT(failures);
}