diff --git a/stdio-common/Makefile b/stdio-common/Makefile
index 840289afd9..8a29980375 100644
--- a/stdio-common/Makefile
+++ b/stdio-common/Makefile
@@ -244,6 +244,7 @@ tests := \
tst-fmemopen2 \
tst-fmemopen3 \
tst-fmemopen4 \
+ tst-fopen \
tst-fphex \
tst-fphex-wide \
tst-fread \
diff --git a/stdio-common/tst-fopen.c b/stdio-common/tst-fopen.c
new file mode 100644
index 0000000000..8c1fefd116
--- /dev/null
+++ b/stdio-common/tst-fopen.c
@@ -0,0 +1,279 @@
+/* Basic test for fopen.
+ Copyright (C) 2025 Free Software Foundation, Inc.
+ 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
+ . */
+
+#include
+#include
+#include
+#include
+
+#include
+#include
+#include
+
+#define APPENDED_TEXT "This is appended text. "
+#define DEFAULT_TEXT "Lorem ipsum dolor sit amet, consectetur " \
+ "adipiscing elit, sed do eiusmod tempor incididunt ut labore et " \
+ "dolore magna aliqua."
+#define MAX_BUFFER_SIZE 300
+
+
+static int
+do_test (void)
+{
+ char *temp_file;
+ FILE *fd_file = NULL;
+ char read_buffer[MAX_BUFFER_SIZE] = "";
+ size_t ret;
+
+ /* Prepare files. */
+ int fd = create_temp_file ("tst-fopen.", &temp_file);
+ TEST_VERIFY_EXIT (fd != -1);
+ fd_file = fdopen (fd, "w");
+ ret = fwrite (DEFAULT_TEXT, sizeof (char), strlen (DEFAULT_TEXT), fd_file);
+ TEST_COMPARE (ret, strlen (DEFAULT_TEXT));
+ xfclose (fd_file);
+
+ /* Test 1: This checks for fopen with mode "r". Open text file for
+ reading. The stream is positioned at the beginning of the file. */
+ printf ("Test 1: This checks for fopen with mode \"r\".\n");
+ fd_file = fopen (temp_file, "r");
+ TEST_COMPARE (ferror (fd_file), 0);
+ TEST_VERIFY (fd_file != NULL);
+ TEST_COMPARE (ftell (fd_file), 0);
+ /* Read should succeed. */
+ ret = fread (read_buffer, sizeof (char), MAX_BUFFER_SIZE, fd_file);
+ TEST_COMPARE (ferror (fd_file), 0);
+ TEST_COMPARE (ret, strlen (DEFAULT_TEXT));
+ TEST_VERIFY (strcmp (read_buffer, DEFAULT_TEXT) == 0);
+ /* Write should fail. */
+ errno = 0;
+ ret = fwrite (DEFAULT_TEXT, sizeof (char), strlen (DEFAULT_TEXT), fd_file);
+ TEST_VERIFY (ferror (fd_file) != 0);
+ TEST_COMPARE (errno, EBADF);
+ TEST_COMPARE (ret, 0);
+ clearerr (fd_file);
+ /* Opening non-existent file should fail. */
+ xfclose (fd_file);
+ errno = 0;
+ fd_file = fopen ("file-that-does-not-exist", "r");
+ TEST_VERIFY (fd_file == NULL);
+ TEST_COMPARE (errno, ENOENT);
+ TEST_VERIFY (fd_file == NULL);
+
+ memset (read_buffer, 0, MAX_BUFFER_SIZE);
+
+ /* Test 2: This checks for fopen with mode "r+". Open for reading and
+ writing. The stream is positioned at the beginning of the file. */
+ printf ("Test 2: This checks for fopen with mode \"r+\".\n");
+ fd_file = fopen (temp_file, "r+");
+ TEST_COMPARE (ferror (fd_file), 0);
+ TEST_VERIFY (fd_file != NULL);
+ TEST_COMPARE (ftell (fd_file), 0);
+ /* Read should succeed. */
+ ret = fread (read_buffer, sizeof (char), MAX_BUFFER_SIZE, fd_file);
+ TEST_COMPARE (ferror (fd_file), 0);
+ TEST_COMPARE (ret, strlen (DEFAULT_TEXT));
+ TEST_VERIFY (strcmp (read_buffer, DEFAULT_TEXT) == 0);
+ fflush (fd_file);
+ /* File position indicator expected at 0 + read bytes. */
+ TEST_COMPARE (ftell (fd_file), ret);
+ /* Write should succeed. */
+ ret = fwrite (DEFAULT_TEXT, sizeof (char), strlen (DEFAULT_TEXT), fd_file);
+ TEST_COMPARE (ferror (fd_file), 0);
+ TEST_COMPARE (ret, strlen (DEFAULT_TEXT));
+ /* Opening non-existent file should fail. */
+ xfclose (fd_file);
+ errno = 0;
+ fd_file = fopen ("file-that-does-not-exist", "r+");
+ TEST_VERIFY (fd_file == NULL);
+ TEST_COMPARE (errno, ENOENT);
+ TEST_VERIFY (fd_file == NULL);
+
+ memset (read_buffer, 0, MAX_BUFFER_SIZE);
+
+ /* Test 3: This checks for fopen with mode "w". Truncate file to zero
+ length or create text file for writing. The stream is positioned
+ at the beginning of the file. */
+ printf ("Test 3: This checks for fopen with mode \"w\".\n");
+ fd_file = fopen (temp_file, "w");
+ TEST_COMPARE (ferror (fd_file), 0);
+ TEST_VERIFY (fd_file != NULL);
+ TEST_COMPARE (ftell (fd_file), 0);
+ /* Read should fail. */
+ errno = 0;
+ ret = fread (read_buffer, sizeof (char), MAX_BUFFER_SIZE, fd_file);
+ TEST_VERIFY (ferror (fd_file) != 0);
+ TEST_COMPARE (errno, EBADF);
+ TEST_COMPARE (ret, 0);
+ clearerr (fd_file);
+ /* Write should succeed. */
+ ret = fwrite (DEFAULT_TEXT, sizeof (char), strlen (DEFAULT_TEXT), fd_file);
+ TEST_COMPARE (ferror (fd_file), 0);
+ TEST_COMPARE (ret, strlen (DEFAULT_TEXT));
+ /* Opening non-existent file should succeed. */
+ xfclose (fd_file);
+ fd_file = fopen ("/tmp/file-that-does-not-exist", "w");
+ TEST_COMPARE (ferror (fd_file), 0);
+ TEST_VERIFY (fd_file != NULL);
+ TEST_COMPARE (ftell (fd_file), 0);
+
+ xfclose (fd_file);
+ remove ("/tmp/file-that-does-not-exist");
+ memset (read_buffer, 0, MAX_BUFFER_SIZE);
+
+ /* Test 4: This checks for fopen with mode "w+". Open for reading and
+ writing. The file is created if it does not exist, otherwise it is
+ truncated. The stream is positioned at the beginning of the file.
+ */
+ printf ("Test 4: This checks for fopen with mode \"w+\".\n");
+ fd_file = fopen (temp_file, "w+");
+ TEST_COMPARE (ferror (fd_file), 0);
+ TEST_VERIFY (fd_file != NULL);
+ TEST_COMPARE (ftell (fd_file), 0);
+ /* Read should succeed. */
+ ret = fread (read_buffer, sizeof (char), MAX_BUFFER_SIZE, fd_file);
+ TEST_COMPARE (ferror (fd_file), 0);
+ TEST_COMPARE (ret, 0);
+ TEST_VERIFY (read_buffer[0] == '\0');
+ /* Write should succeed. */
+ ret = fwrite (DEFAULT_TEXT, sizeof (char), strlen (DEFAULT_TEXT), fd_file);
+ TEST_COMPARE (ferror (fd_file), 0);
+ TEST_COMPARE (ret, strlen (DEFAULT_TEXT));
+ /* Opening non-existent file should succeed. */
+ xfclose (fd_file);
+ fd_file = fopen ("/tmp/file-that-does-not-exist", "w+");
+ TEST_COMPARE (ferror (fd_file), 0);
+ TEST_VERIFY (fd_file != NULL);
+ TEST_COMPARE (ftell (fd_file), 0);
+
+ xfclose (fd_file);
+ remove ("/tmp/file-that-does-not-exist");
+ memset (read_buffer, 0, MAX_BUFFER_SIZE);
+
+ /* Test 5: This checks for fopen with mode "a". Open for appending
+ (writing at end of file). The file is created if it does not
+ exist. The stream is positioned at the end of the file. */
+ printf ("Test 5: This checks for fopen with mode \"a\".\n");
+ fd_file = fopen (temp_file, "a");
+ TEST_COMPARE (ferror (fd_file), 0);
+ TEST_VERIFY (fd_file != NULL);
+ TEST_COMPARE (ftell (fd_file), strlen (DEFAULT_TEXT));
+ /* Read should fail. */
+ errno = 0;
+ ret = fread (read_buffer, sizeof (char), MAX_BUFFER_SIZE, fd_file);
+ TEST_VERIFY (ferror (fd_file) != 0);
+ TEST_COMPARE (errno, EBADF);
+ TEST_COMPARE (ret, 0);
+ clearerr (fd_file);
+ /* Write should succeed. */
+ ret = fwrite (APPENDED_TEXT, sizeof (char), strlen (APPENDED_TEXT), fd_file);
+ TEST_COMPARE (ferror (fd_file), 0);
+ TEST_COMPARE (ret, strlen (APPENDED_TEXT));
+ /* The file position indicator for the stream is advanced by the
+ * number of bytes successfully read or written. */
+ TEST_COMPARE (ftell (fd_file), strlen (DEFAULT_TEXT) + ret);
+ /* Opening non-existent file should succeed. */
+ xfclose (fd_file);
+ fd_file = fopen ("/tmp/file-that-does-not-exist", "a");
+ TEST_COMPARE (ferror (fd_file), 0);
+ TEST_VERIFY (fd_file != NULL);
+ TEST_COMPARE (ftell (fd_file), 0);
+
+ xfclose (fd_file);
+ remove ("/tmp/file-that-does-not-exist");
+ memset (read_buffer, 0, MAX_BUFFER_SIZE);
+
+ /* Test 6: This checks for fopen with mode "a+". Open for reading and
+ appending (writing at end of file). The file is created if it does
+ not exist. Output is always appended to the end of the file. The
+ initial file position for reading is at the beginning of the file,
+ but it is advanced to the end prior to each write. */
+ printf ("Test 6: This checks for fopen with mode \"a+\".\n");
+ errno = 0;
+ fd_file = fopen (temp_file, "a+");
+ TEST_COMPARE (errno, 0);
+ TEST_VERIFY (fd_file != NULL);
+ TEST_COMPARE (ftell (fd_file), 0);
+ /* Read should succeed. */
+ ret = fread (read_buffer, sizeof (char), MAX_BUFFER_SIZE, fd_file);
+ TEST_COMPARE (ferror (fd_file), 0);
+ TEST_COMPARE (ret, strlen (DEFAULT_TEXT) + strlen (APPENDED_TEXT));
+ TEST_VERIFY (strcmp (read_buffer, DEFAULT_TEXT APPENDED_TEXT) == 0);
+ /* Write should succeed. */
+ const char* SECOND_APPEND = "This is second append.";
+ ret = fwrite (SECOND_APPEND, sizeof (char), strlen (SECOND_APPEND), fd_file);
+ TEST_COMPARE (ferror (fd_file), 0);
+ TEST_COMPARE (ret, strlen (SECOND_APPEND));
+ /* The file position indicator for the stream is advanced by the
+ number of bytes successfully read or written. */
+ TEST_COMPARE (ftell (fd_file),
+ strlen (DEFAULT_TEXT) + strlen (APPENDED_TEXT) + ret);
+ /* Opening non-existent file should succeed. */
+ xfclose (fd_file);
+ fd_file = fopen ("/tmp/file-that-does-not-exist", "a+");
+ TEST_COMPARE (ferror (fd_file), 0);
+ TEST_VERIFY (fd_file != NULL);
+ TEST_COMPARE (ftell (fd_file), 0);
+
+ xfclose (fd_file);
+ remove ("/tmp/file-that-does-not-exist");
+ memset (read_buffer, 0, MAX_BUFFER_SIZE);
+
+ /* Test 7: This checks for fopen with other valid modes set, such as
+ "rc", "we" or "am". The test calls fopen with these modes and
+ checks that no errors appear. */
+ printf ("Test 7: This checks for fopen with other valid modes set, "
+ "such as \"rc\", \"we\" or \"am\".\n");
+ /* These modes all operate correctly with the file already present. */
+ static const char *valid_modes[] =
+ { "rc", "we", "am", "r+x", "wb+", "ab", 0 };
+ const char **p = valid_modes;
+ while (*p != 0)
+ {
+ fd_file = fopen (temp_file, *p);
+ TEST_COMPARE (ferror (fd_file), 0);
+ TEST_VERIFY (fd_file != NULL);
+ xfclose (fd_file);
+ ++p;
+ }
+
+ /* Test 8: This checks for fopen with invalid modes. The test calls
+ fopen with these modes and checks that opening existing files with
+ invalid mode fails and that opening non-existing files with invalid
+ mode doesn't create a new file. */
+ printf ("Test 8: This checks for fopen with invalid modes.\n");
+ static const char *invalid_modes[] = { "0", "tr", "z", "x", " ", 0 };
+ p = invalid_modes;
+ while (*p != 0)
+ {
+ errno = 0;
+ fd_file = fopen (temp_file, *p);
+ TEST_VERIFY (fd_file == NULL);
+ TEST_COMPARE (errno, EINVAL);
+ errno = 0;
+ fd_file = fopen ("/tmp/file-that-does-not-exist", *p);
+ TEST_VERIFY (fd_file == NULL);
+ TEST_COMPARE (errno, EINVAL);
+ ++p;
+ TEST_VERIFY (access ("/tmp/file-that-does-not-exist", F_OK) == -1);
+ }
+
+ return 0;
+}
+
+#include
diff --git a/sysdeps/pthread/Makefile b/sysdeps/pthread/Makefile
index a123e28a57..5947db43f3 100644
--- a/sysdeps/pthread/Makefile
+++ b/sysdeps/pthread/Makefile
@@ -154,6 +154,7 @@ tests += \
tst-exit3 \
tst-flock1 \
tst-flock2 \
+ tst-fopen-threaded \
tst-fork1 \
tst-fork2 \
tst-fork3 \
diff --git a/sysdeps/pthread/tst-fopen-threaded.c b/sysdeps/pthread/tst-fopen-threaded.c
new file mode 100644
index 0000000000..5c792c93e3
--- /dev/null
+++ b/sysdeps/pthread/tst-fopen-threaded.c
@@ -0,0 +1,250 @@
+/* Test for fread and fwrite with multiple threads.
+ Copyright (C) 2025 Free Software Foundation, Inc.
+ 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
+ . */
+
+/* Description of test intent.
+ The test creates NUM_THREADS threads for reading and writing to the
+ prepared file. The prepared file contains 'NUM_THREADS - 1' bytes
+ where each byte is unique number from 0 to 'NUM_THREADS - 2'. If all
+ operations are correctly multi-threaded safe then all concurent read
+ operations should succeed and read a unique 1 byte value. The last
+ thread to read should get an EOF. In concurrent write, all write
+ operations should succeed and the file should contain all unique 1
+ byte values from 0 to 'NUM_THREADS - 1'. Both concurrent read and
+ concurrent write tests are repeated ITERS times to increase
+ the probability of detecting concurrency issues. */
+
+#include
+#include
+#include
+#include
+#include
+#include
+
+#include
+#include
+#include
+#include
+
+#define NUM_THREADS 100
+#define ITERS 10
+
+char *temp_file;
+pthread_barrier_t barrier;
+
+struct thread_data
+{
+ FILE *fd;
+ /* Read value or value to be written. */
+ unsigned char value;
+ bool eof;
+};
+
+static void *
+threadReadRoutine (void *argv)
+{
+ struct thread_data *my_data;
+ unsigned char read_buffer;
+ int ret = 0;
+ my_data = (struct thread_data *) argv;
+ /* Wait for all threads to be ready to read. */
+ xpthread_barrier_wait (&barrier);
+
+ ret =
+ fread (&read_buffer, sizeof (char), sizeof (read_buffer), my_data->fd);
+ if (feof (my_data->fd) != 0)
+ {
+ clearerr (my_data->fd);
+ my_data->eof = true;
+ }
+ else
+ {
+ TEST_COMPARE (ret, 1);
+ /* Save the read value. */
+ my_data->value = read_buffer;
+ }
+ TEST_COMPARE (ferror (my_data->fd), 0);
+ return NULL;
+}
+
+void *
+threadWriteRoutine (void *argv)
+{
+ struct thread_data *my_data;
+ int ret = 0;
+ my_data = (struct thread_data *) argv;
+ /* Wait for all threads to be ready to write. */
+ xpthread_barrier_wait (&barrier);
+
+ ret = fwrite (&my_data->value, sizeof (unsigned char), 1, my_data->fd);
+ TEST_COMPARE (ferror (my_data->fd), 0);
+ TEST_COMPARE (feof (my_data->fd), 0);
+ TEST_COMPARE (ret, 1);
+ return NULL;
+}
+
+void *
+threadOpenCloseRoutine (void *argv)
+{
+ /* Wait for all threads to be ready to call fopen and fclose. */
+ xpthread_barrier_wait (&barrier);
+
+ FILE *fd = xfopen ("/tmp/openclosetest", "w+");
+ xfclose (fd);
+ return NULL;
+}
+
+static int
+do_test (void)
+{
+ FILE *fd_file = NULL;
+ unsigned char buffer[NUM_THREADS] = "0";
+ size_t ret = 0;
+ pthread_t threads[NUM_THREADS];
+ struct thread_data thread_data_array[NUM_THREADS];
+ bool present_values[NUM_THREADS] = { false };
+
+ /* Prepare files. */
+ for (int i = 0; i < NUM_THREADS; i++)
+ buffer[i] = i;
+ int fd = create_temp_file ("tst-fopen.", &temp_file);
+ TEST_VERIFY_EXIT (fd != -1);
+ fd_file = fdopen (fd, "w");
+ /* NUM_THREADS - 1: last thread will read EOF */
+ ret = fwrite (buffer, sizeof (unsigned char), NUM_THREADS - 1, fd_file);
+ TEST_COMPARE (ret, NUM_THREADS - 1);
+ xfclose (fd_file);
+
+ /* Test 1: Concurrent read. */
+ for (int reps = 1; reps <= ITERS; reps++)
+ {
+ fd_file = xfopen (temp_file, "r");
+ xpthread_barrier_init (&barrier, NULL, NUM_THREADS);
+ for (int i = 0; i < NUM_THREADS; i++)
+ {
+ thread_data_array[i].fd = fd_file;
+ /* Initialize with highest possible value so it's easier to debug if
+ anything goes wrong. */
+ thread_data_array[i].value = 255;
+ thread_data_array[i].eof = false;
+
+ threads[i] =
+ xpthread_create (support_small_stack_thread_attribute (),
+ threadReadRoutine,
+ (void *) &thread_data_array[i]);
+ }
+
+ for (int i = 0; i < NUM_THREADS; i++)
+ {
+ xpthread_join (threads[i]);
+ }
+ xpthread_barrier_destroy (&barrier);
+ xfclose (fd_file);
+
+ /* Verify read values. */
+ int eof_cnt = 0;
+ for (int i = 0; i < NUM_THREADS; i++)
+ present_values[i] = false;
+ for (int i = 0; i < NUM_THREADS; i++)
+ {
+ if (thread_data_array[i].eof)
+ {
+ /* EOF was read. */
+ present_values[NUM_THREADS - 1] = true;
+ eof_cnt++;
+ }
+ else
+ {
+ /* The same value shouldn't be read twice. */
+ TEST_VERIFY (!present_values[thread_data_array[i].value]);
+ present_values[thread_data_array[i].value] = true;
+ }
+ }
+ /* EOF is read exactly once. */
+ TEST_COMPARE (eof_cnt, 1);
+ for (int i = 0; i < NUM_THREADS; i++)
+ {
+ /* All values should be read. */
+ TEST_VERIFY (present_values[i]);
+ }
+ }
+
+ /* Test 2: Concurrent write. */
+ for (int reps = 1; reps <= ITERS; reps++)
+ {
+ fd_file = xfopen (temp_file, "w");
+ xpthread_barrier_init (&barrier, NULL, NUM_THREADS);
+ for (int i = 0; i < NUM_THREADS; i++)
+ {
+ thread_data_array[i].fd = fd_file;
+ thread_data_array[i].value = i;
+
+ threads[i] =
+ xpthread_create (support_small_stack_thread_attribute (),
+ threadWriteRoutine,
+ (void *) &thread_data_array[i]);
+ }
+
+ for (int i = 0; i < NUM_THREADS; i++)
+ {
+ xpthread_join (threads[i]);
+ }
+ xpthread_barrier_destroy (&barrier);
+ xfclose (fd_file);
+
+ /* Verify written values. */
+ for (int i = 0; i < NUM_THREADS; i++)
+ present_values[i] = false;
+ memset (buffer, 0, NUM_THREADS);
+ fd_file = xfopen (temp_file, "r");
+ ret = fread (buffer, sizeof (unsigned char), NUM_THREADS, fd_file);
+ TEST_COMPARE (ret, NUM_THREADS);
+ for (int i = 0; i < NUM_THREADS; i++)
+ {
+ /* The same value shouldn't be written twice. */
+ TEST_VERIFY (!present_values[buffer[i]]);
+ present_values[buffer[i]] = true;
+ }
+ for (int i = 0; i < NUM_THREADS; i++)
+ {
+ /* All values should be written. */
+ TEST_VERIFY (present_values[i]);
+ }
+ xfclose (fd_file);
+ }
+
+ /* Test 3: Concurrent open/close. */
+ for (int reps = 1; reps <= ITERS; reps++)
+ {
+ xpthread_barrier_init (&barrier, NULL, NUM_THREADS);
+ for (int i = 0; i < NUM_THREADS; i++)
+ {
+ threads[i] =
+ xpthread_create (support_small_stack_thread_attribute (),
+ threadOpenCloseRoutine, NULL);
+ }
+ for (int i = 0; i < NUM_THREADS; i++)
+ {
+ xpthread_join (threads[i]);
+ }
+ xpthread_barrier_destroy (&barrier);
+ }
+
+ return 0;
+}
+
+#include