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/* Test ungetc behavior with malloc failures.
Copyright The GNU Toolchain Authors.
This file is part of the GNU C Library.
The GNU C Library is free software; you can redistribute it and/or
modify it under the terms of the GNU Lesser General Public
License as published by the Free Software Foundation; either
version 2.1 of the License, or (at your option) any later version.
The GNU C Library is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General Public
License along with the GNU C Library; if not, see
<https://www.gnu.org/licenses/>. */
#include <dlfcn.h>
#include <stdio.h>
#include <string.h>
#include <support/check.h>
#include <support/support.h>
#include <support/temp_file.h>
#include <support/xstdio.h>
static volatile bool fail = false;
/* Induce a malloc failure whenever FAIL is set; we use the __LIBC_MALLOC entry
point to avoid the other alternative, which is RTLD_NEXT. */
void *
malloc (size_t sz)
{
if (fail)
return NULL;
static void *(*real_malloc) (size_t);
if (real_malloc == NULL)
real_malloc = dlsym (RTLD_NEXT, "malloc");
return real_malloc (sz);
}
static int
do_test (void)
{
char *filename = NULL;
struct stat props = {};
size_t bufsz = 0;
create_temp_file ("tst-ungetc-nomem.", &filename);
if (stat (filename, &props) != 0)
FAIL_EXIT1 ("Could not get file status: %m\n");
FILE *fp = fopen (filename, "w");
/* The libio buffer sizes are the same as block size. This is to ensure that
the test runs at the read underflow boundary as well. */
bufsz = props.st_blksize + 2;
char *buf = xmalloc (bufsz);
memset (buf, 'a', bufsz);
if (fwrite (buf, sizeof (char), bufsz, fp) != bufsz)
FAIL_EXIT1 ("fwrite failed: %m\n");
xfclose (fp);
/* Begin test. */
fp = xfopen (filename, "r");
while (!feof (fp))
{
/* Reset the pushback buffer state. */
fseek (fp, 0, SEEK_CUR);
fail = true;
/* 1: First ungetc should always succeed, as the standard requires. */
TEST_COMPARE (ungetc ('b', fp), 'b');
/* 2: This will result in resizing, which should fail. */
TEST_COMPARE (ungetc ('c', fp), EOF);
/* 3: Now allow the resizing, which should immediately fill up the buffer
too, since this allocates only double the current buffer, i.e.
2-bytes. */
fail = false;
TEST_COMPARE (ungetc ('d', fp), 'd');
/* 4: And fail again because this again forces an alloc, which fails. */
fail = true;
TEST_COMPARE (ungetc ('e', fp), EOF);
/* 5: Enable allocations again so that we now get a 4-byte buffer. Now
both calls should work. */
fail = false;
TEST_COMPARE (ungetc ('f', fp), 'f');
fail = true;
TEST_COMPARE (ungetc ('g', fp), 'g');
/* Drain out the x's. */
TEST_COMPARE (fgetc (fp), 'g');
TEST_COMPARE (fgetc (fp), 'f');
TEST_COMPARE (fgetc (fp), 'd');
/* Finally, drain out the first char we had pushed back, followed by one
more char from the stream, if present. */
TEST_COMPARE (fgetc (fp), 'b');
char c = fgetc (fp);
if (!feof (fp))
TEST_COMPARE (c, 'a');
}
/* Final sanity check before we're done. */
TEST_COMPARE (ferror (fp), 0);
xfclose (fp);
return 0;
}
#include <support/test-driver.c>
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