system/popen: Avoid copying FILE

system/popen/popen.c

@@ -32,6 +32,7 @@
 #include <stdlib.h>
 #include <unistd.h>
 #include <string.h>
+#include <semaphore.h>
 #include <sched.h>
 #include <spawn.h>
 #include <assert.h>
@@ -45,17 +46,78 @@
  * Private Types
  ****************************************************************************/
 
-/* struct popen_file_s is a cast compatible version of FILE that contains
- * the additional PID of the shell processes needed by pclose().
- */
-
 struct popen_file_s
 {
-  FILE copy;
-  FILE *original;
+  FAR struct popen_file_s *flink;
+  FAR FILE *stream;
   pid_t shell;
 };
 
+/****************************************************************************
+ * Private Data
+ ****************************************************************************/
+
+static sem_t g_popen_sem = SEM_INITIALIZER(1);
+static FAR struct popen_file_s *g_popen_files;
+
+/****************************************************************************
+ * Private Functions
+ ****************************************************************************/
+
+static void popen_lock(void)
+{
+  while (sem_wait(&g_popen_sem) < 0)
+    {
+      int errcode = errno;
+
+      DEBUGASSERT(errcode == EINTR || errcode == ECANCELED);
+      UNUSED(errcode);
+    }
+}
+
+static void popen_unlock(void)
+{
+  sem_post(&g_popen_sem);
+}
+
+static void popen_add_file(FAR struct popen_file_s *container)
+{
+  popen_lock();
+  container->flink = g_popen_files;
+  g_popen_files = container;
+  popen_unlock();
+}
+
+static FAR struct popen_file_s *popen_remove_file(FAR FILE *stream)
+{
+  FAR struct popen_file_s *container;
+  FAR struct popen_file_s *prev = NULL;
+
+  popen_lock();
+  for (container = g_popen_files; container != NULL;
+       container = container->flink)
+    {
+      if (container->stream == stream)
+        {
+          if (prev == NULL)
+            {
+              g_popen_files = container->flink;
+            }
+          else
+            {
+              prev->flink = container->flink;
+            }
+
+          break;
+        }
+
+      prev = container;
+    }
+
+  popen_unlock();
+  return container;
+}
+
 /****************************************************************************
  * Public Functions
  ****************************************************************************/
@@ -193,8 +255,8 @@ FILE *popen(FAR const char *command, FAR const char *mode)
 
   /* Create the FILE stream return reference */
 
-  container->original = fdopen(retfd, mode);
-  if (container->original == NULL)
+  container->stream = fdopen(retfd, mode);
+  if (container->stream == NULL)
     {
       errcode = errno;
       goto errout_with_pipe;
@@ -329,10 +391,10 @@ FILE *popen(FAR const char *command, FAR const char *mode)
       ioctl(retfd, FIOCLEX, 0);
     }
 
-  /* Finale and return input input/output stream */
+  /* Save the shell PID for pclose() without depending on FILE internals. */
 
-  memcpy(&container->copy, container->original, sizeof(FILE));
-  return &container->copy;
+  popen_add_file(container);
+  return container->stream;
 
 errout_with_actions:
   posix_spawn_file_actions_destroy(&file_actions);
@@ -341,7 +403,7 @@ FILE *popen(FAR const char *command, FAR const char *mode)
   posix_spawnattr_destroy(&attr);
 
 errout_with_stream:
-  fclose(container->original);
+  fclose(container->stream);
 
 errout_with_pipe:
   close(fd[0]);
@@ -399,28 +461,23 @@ FILE *popen(FAR const char *command, FAR const char *mode)
 
 int pclose(FILE *stream)
 {
-  FAR struct popen_file_s *container = (FAR struct popen_file_s *)stream;
-  FILE *original;
+  FAR struct popen_file_s *container;
   pid_t shell;
 #ifdef CONFIG_SCHED_WAITPID
   int status;
   int result;
 #endif
 
-  DEBUGASSERT(container != NULL && container->original != NULL);
-  original = container->original;
-
-  /* Set the state of the original file descriptor to the state of the
-   * working copy
-   */
-
-  memcpy(original, &container->copy, sizeof(FILE));
+  DEBUGASSERT(stream != NULL);
 
-  /* Then close the original and free the container (saving the PID of the
-   * shell process)
-   */
+  container = popen_remove_file(stream);
+  if (container == NULL)
+    {
+      errno = EINVAL;
+      return ERROR;
+    }
 
-  fclose(original);
+  fclose(stream);
 
   shell = container->shell;
   free(container);

testing/libc/popen/CMakeLists.txt

@@ -0,0 +1,33 @@
+# ##############################################################################
+# apps/testing/libc/popen/CMakeLists.txt
+#
+# SPDX-License-Identifier: Apache-2.0
+#
+# Licensed to the Apache Software Foundation (ASF) under one or more contributor
+# license agreements.  See the NOTICE file distributed with this work for
+# additional information regarding copyright ownership.  The ASF licenses this
+# file to you under the Apache License, Version 2.0 (the "License"); you may not
+# use this file except in compliance with the License.  You may obtain a copy of
+# the License at
+#
+# http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+# WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.  See the
+# License for the specific language governing permissions and limitations under
+# the License.
+#
+# ##############################################################################
+
+if(CONFIG_TESTING_POPEN_TEST)
+  nuttx_add_application(
+    NAME
+    popen_test
+    STACKSIZE
+    4096
+    MODULE
+    ${CONFIG_TESTING_POPEN_TEST}
+    SRCS
+    popen_test.c)
+endif()

testing/libc/popen/Kconfig

@@ -0,0 +1,12 @@
+#
+# For a description of the syntax of this configuration file,
+# see the file kconfig-language.txt in the NuttX tools repository.
+#
+
+config TESTING_POPEN_TEST
+	tristate "popen() test"
+	default n
+	depends on SYSTEM_POPEN
+	depends on !NSH_DISABLE_ECHO
+	---help---
+		Test reading from popen() streams and closing them with pclose().

testing/libc/popen/Make.defs

@@ -0,0 +1,25 @@
+############################################################################
+# apps/testing/libc/popen/Make.defs
+#
+# SPDX-License-Identifier: Apache-2.0
+#
+# Licensed to the Apache Software Foundation (ASF) under one or more
+# contributor license agreements.  See the NOTICE file distributed with
+# this work for additional information regarding copyright ownership.  The
+# ASF licenses this file to you under the Apache License, Version 2.0 (the
+# "License"); you may not use this file except in compliance with the
+# License.  You may obtain a copy of the License at
+#
+#   http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+# WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.  See the
+# License for the specific language governing permissions and limitations
+# under the License.
+#
+############################################################################
+
+ifneq ($(CONFIG_TESTING_POPEN_TEST),)
+CONFIGURED_APPS += $(APPDIR)/testing/libc/popen
+endif

testing/libc/popen/Makefile

@@ -0,0 +1,34 @@
+############################################################################
+# apps/testing/libc/popen/Makefile
+#
+# SPDX-License-Identifier: Apache-2.0
+#
+# Licensed to the Apache Software Foundation (ASF) under one or more
+# contributor license agreements.  See the NOTICE file distributed with
+# this work for additional information regarding copyright ownership.  The
+# ASF licenses this file to you under the Apache License, Version 2.0 (the
+# "License"); you may not use this file except in compliance with the
+# License.  You may obtain a copy of the License at
+#
+#   http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+# WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.  See the
+# License for the specific language governing permissions and limitations
+# under the License.
+#
+############################################################################
+
+include $(APPDIR)/Make.defs
+
+# popen() test tool
+
+PROGNAME = popen_test
+PRIORITY = SCHED_PRIORITY_DEFAULT
+STACKSIZE = 4096
+MODULE = $(CONFIG_TESTING_POPEN_TEST)
+
+MAINSRC = popen_test.c
+
+include $(APPDIR)/Application.mk