diff options
Diffstat (limited to 'lib/libc/tests/stdio/flushlbuf_test.c')
| -rw-r--r-- | lib/libc/tests/stdio/flushlbuf_test.c | 155 |
1 files changed, 155 insertions, 0 deletions
diff --git a/lib/libc/tests/stdio/flushlbuf_test.c b/lib/libc/tests/stdio/flushlbuf_test.c new file mode 100644 index 000000000000..3f8a6378f933 --- /dev/null +++ b/lib/libc/tests/stdio/flushlbuf_test.c @@ -0,0 +1,155 @@ +/*- + * Copyright (c) 2023 Klara, Inc. + * + * SPDX-License-Identifier: BSD-2-Clause + */ + +#include <errno.h> +#include <stdio.h> + +#include <atf-c.h> + +#define BUFSIZE 16 + +static const char seq[] = + "ABCDEFGHIJKLMNOPQRSTUVWXYZ" + "abcdefghijklmnopqrstuvwxyz" + "0123456789+/"; + +struct stream { + char buf[BUFSIZE]; + unsigned int len; + unsigned int pos; +}; + +static int +writefn(void *cookie, const char *buf, int len) +{ + struct stream *s = cookie; + int written = 0; + + if (len <= 0) + return (0); + while (len > 0 && s->pos < s->len) { + s->buf[s->pos++] = *buf++; + written++; + len--; + } + if (written > 0) + return (written); + errno = EAGAIN; + return (-1); +} + +ATF_TC_WITHOUT_HEAD(flushlbuf_partial); +ATF_TC_BODY(flushlbuf_partial, tc) +{ + static struct stream s; + static char buf[BUFSIZE + 1]; + FILE *f; + unsigned int i = 0; + int ret = 0; + + /* + * Create the stream and its buffer, print just enough characters + * to the stream to fill the buffer without triggering a flush, + * then check the state. + */ + s.len = BUFSIZE / 2; // write will fail after this amount + ATF_REQUIRE((f = fwopen(&s, writefn)) != NULL); + ATF_REQUIRE(setvbuf(f, buf, _IOLBF, BUFSIZE) == 0); + while (i < BUFSIZE) + if ((ret = fprintf(f, "%c", seq[i++])) < 0) + break; + ATF_CHECK_EQ(BUFSIZE, i); + ATF_CHECK_EQ(seq[i - 1], buf[BUFSIZE - 1]); + ATF_CHECK_EQ(1, ret); + ATF_CHECK_EQ(0, s.pos); + + /* + * At this point, the buffer is full but writefn() has not yet + * been called. The next fprintf() call will trigger a preemptive + * fflush(), and writefn() will consume s.len characters before + * returning EAGAIN, causing fprintf() to fail without having + * written anything (which is why we don't increment i here). + */ + ret = fprintf(f, "%c", seq[i]); + ATF_CHECK_ERRNO(EAGAIN, ret < 0); + ATF_CHECK_EQ(s.len, s.pos); + + /* + * We have consumed s.len characters from the buffer, so continue + * printing until it is full again and check that no overflow has + * occurred yet. + */ + while (i < BUFSIZE + s.len) + fprintf(f, "%c", seq[i++]); + ATF_CHECK_EQ(BUFSIZE + s.len, i); + ATF_CHECK_EQ(seq[i - 1], buf[BUFSIZE - 1]); + ATF_CHECK_EQ(0, buf[BUFSIZE]); + + /* + * The straw that breaks the camel's back: libc fails to recognize + * that the buffer is full and continues to write beyond its end. + */ + fprintf(f, "%c", seq[i++]); + ATF_CHECK_EQ(0, buf[BUFSIZE]); +} + +ATF_TC_WITHOUT_HEAD(flushlbuf_full); +ATF_TC_BODY(flushlbuf_full, tc) +{ + static struct stream s; + static char buf[BUFSIZE]; + FILE *f; + unsigned int i = 0; + int ret = 0; + + /* + * Create the stream and its buffer, print just enough characters + * to the stream to fill the buffer without triggering a flush, + * then check the state. + */ + s.len = 0; // any attempt to write will fail + ATF_REQUIRE((f = fwopen(&s, writefn)) != NULL); + ATF_REQUIRE(setvbuf(f, buf, _IOLBF, BUFSIZE) == 0); + while (i < BUFSIZE) + if ((ret = fprintf(f, "%c", seq[i++])) < 0) + break; + ATF_CHECK_EQ(BUFSIZE, i); + ATF_CHECK_EQ(seq[i - 1], buf[BUFSIZE - 1]); + ATF_CHECK_EQ(1, ret); + ATF_CHECK_EQ(0, s.pos); + + /* + * At this point, the buffer is full but writefn() has not yet + * been called. The next fprintf() call will trigger a preemptive + * fflush(), and writefn() will immediately return EAGAIN, causing + * fprintf() to fail without having written anything (which is why + * we don't increment i here). + */ + ret = fprintf(f, "%c", seq[i]); + ATF_CHECK_ERRNO(EAGAIN, ret < 0); + ATF_CHECK_EQ(s.len, s.pos); + + /* + * Now make our stream writeable. + */ + s.len = sizeof(s.buf); + + /* + * Flush the stream again. The data we failed to write previously + * should still be in the buffer and will now be written to the + * stream. + */ + ATF_CHECK_EQ(0, fflush(f)); + ATF_CHECK_EQ(seq[0], s.buf[0]); +} + +ATF_TP_ADD_TCS(tp) +{ + ATF_TP_ADD_TC(tp, flushlbuf_partial); + ATF_TP_ADD_TC(tp, flushlbuf_full); + + return (atf_no_error()); +} |