source/blender/blenkernel/intern/appdir.c

@@ -17,6 +17,7 @@
 #include "BLI_string.h"
 #include "BLI_string_utf8.h"
 #include "BLI_string_utils.h"
+#include "BLI_tempfile.h"
 #include "BLI_utildefines.h"
 
 #include "BKE_appdir.h" /* own include */
@@ -1089,7 +1090,7 @@ void BKE_appdir_app_templates(ListBase *templates)
  * Also make sure the temp dir has a trailing slash
  *
  * \param tempdir: The full path to the temporary temp directory.
- * \param tempdir_len: The size of the \a tempdir buffer.
+ * \param tempdir_maxlen: The size of the \a tempdir buffer.
  * \param userdir: Directory specified in user preferences (may be NULL).
  * note that by default this is an empty string, only use when non-empty.
  */
@@ -1098,37 +1099,14 @@ static void where_is_temp(char *tempdir, const size_t tempdir_maxlen, const char
 
   tempdir[0] = '\0';
 
-  if (userdir && BLI_is_dir(userdir)) {
+  if (userdir && userdir[0] != '\0' && BLI_is_dir(userdir)) {
     BLI_strncpy(tempdir, userdir, tempdir_maxlen);
-  }
-
-  if (tempdir[0] == '\0') {
-    const char *env_vars[] = {
-#ifdef WIN32
-        "TEMP",
-#else
-        /* Non standard (could be removed). */
-        "TMP",
-        /* Posix standard. */
-        "TMPDIR",
-#endif
-    };
-    for (int i = 0; i < ARRAY_SIZE(env_vars); i++) {
-      const char *tmp = BLI_getenv(env_vars[i]);
-      if (tmp && (tmp[0] != '\0') && BLI_is_dir(tmp)) {
-        BLI_strncpy(tempdir, tmp, tempdir_maxlen);
-        break;
-      }
-    }
-  }
-
-  if (tempdir[0] == '\0') {
-    BLI_strncpy(tempdir, "/tmp/", tempdir_maxlen);
-  }
-  else {
-    /* add a trailing slash if needed */
+    /* Add a trailing slash if needed. */
     BLI_path_slash_ensure(tempdir, tempdir_maxlen);
+    return;
   }
+
+  BLI_temp_directory_path_get(tempdir, tempdir_maxlen);
 }
 
 static void tempdir_session_create(char *tempdir_session,

source/blender/blenlib/BLI_tempfile.h

@@ -0,0 +1,27 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later
+ * Copyright 2023 Blender Foundation. */
+
+/** \file
+ * \ingroup bli
+ */
+
+#pragma once
+
+#include "BLI_sys_types.h"
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+/* Get the path to a directory suitable for temporary files.
+ *
+ * The return path is guaranteed to exist and to be a directory, as well as to contain a trailing
+ * directory separator.
+ *
+ * At maximum the buffer_size number of characters is written to the temp_directory. The directory
+ * path is always null-terminated. */
+void BLI_temp_directory_path_get(char *temp_directory, const size_t buffer_size);
+
+#ifdef __cplusplus
+}
+#endif

source/blender/blenlib/CMakeLists.txt

@@ -147,6 +147,7 @@ set(SRC
   intern/task_pool.cc
   intern/task_range.cc
   intern/task_scheduler.cc
+  intern/tempfile.c
   intern/threads.cc
   intern/time.c
   intern/timecode.c
@@ -347,6 +348,7 @@ set(SRC
   BLI_system.h
   BLI_task.h
   BLI_task.hh
+  BLI_tempfile.h
   BLI_threads.h
   BLI_timecode.h
   BLI_timeit.hh
@@ -533,6 +535,7 @@ if(WITH_GTESTS)
     tests/BLI_string_utf8_test.cc
     tests/BLI_task_graph_test.cc
     tests/BLI_task_test.cc
+    tests/BLI_tempfile_test.cc
     tests/BLI_uuid_test.cc
     tests/BLI_vector_set_test.cc
     tests/BLI_vector_test.cc

source/blender/blenlib/intern/tempfile.c

@@ -0,0 +1,42 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later
+ * Copyright 2023 Blender Foundation. */
+
+#include "BLI_tempfile.h"
+
+#include "BLI_fileops.h"
+#include "BLI_path_util.h"
+#include "BLI_string.h"
+
+void BLI_temp_directory_path_get(char *temp_directory, const size_t buffer_size)
+{
+  temp_directory[0] = '\0';
+
+  const char *env_vars[] = {
+#ifdef WIN32
+      "TEMP",
+#else
+      /* Non standard (could be removed). */
+      "TMP",
+      /* Posix standard. */
+      "TMPDIR",
+#endif
+  };
+
+  for (int i = 0; i < ARRAY_SIZE(env_vars); i++) {
+    const char *tmp = BLI_getenv(env_vars[i]);
+    if (tmp && (tmp[0] != '\0') && BLI_is_dir(tmp)) {
+      BLI_strncpy(temp_directory, tmp, buffer_size);
+      break;
+    }
+  }
+
+  if (temp_directory[0] == '\0') {
+    BLI_strncpy(temp_directory, "/tmp/", buffer_size);
+  }
+  else {
+    /* Add a trailing slash if needed. */
+    BLI_path_slash_ensure(temp_directory, buffer_size);
+  }
+
+  BLI_dir_create_recursive(temp_directory);
+}

source/blender/blenlib/tests/BLI_fileops_test.cc

@@ -1,11 +1,16 @@
 /* SPDX-License-Identifier: Apache-2.0 */
+
 #include "testing/testing.h"
 
 #include "BLI_fileops.hh"
 #include "BLI_path_util.h"
 #include "BLI_string.h"
+#include "BLI_system.h"
+#include "BLI_tempfile.h"
 #include "BLI_threads.h"
 
+#include BLI_SYSTEM_PID_H
+
 namespace blender::tests {
 
 class ChangeWorkingDirectoryTest : public testing::Test {
@@ -26,6 +31,20 @@ class ChangeWorkingDirectoryTest : public testing::Test {
 
     BLI_threadapi_exit();
   }
+
+  /* Make a pseudo-unique file name file within the temp directory in a cross-platform manner. */
+  static std::string make_pseudo_unique_temp_filename()
+  {
+    char temp_dir[FILE_MAX];
+    BLI_temp_directory_path_get(temp_dir, sizeof(temp_dir));
+
+    const std::string directory_name = "blender_test_" + std::to_string(getpid());
+
+    char filepath[FILE_MAX];
+    BLI_path_join(filepath, sizeof(filepath), temp_dir, directory_name.c_str());
+
+    return filepath;
+  }
 };
 
 TEST(fileops, fstream_open_string_filename)
@@ -71,7 +90,7 @@ TEST_F(ChangeWorkingDirectoryTest, change_working_directory)
   ASSERT_TRUE(original_cwd == original_cwd_buff)
       << "Returned CWD path unexpectedly different than given char buffer.";
 
-  std::string temp_file_name(std::tmpnam(nullptr));
+  std::string temp_file_name = make_pseudo_unique_temp_filename();
   test_temp_dir = temp_file_name + "_новый";
 
   if (BLI_exists(test_temp_dir.c_str())) {

source/blender/blenlib/tests/BLI_tempfile_test.cc

@@ -0,0 +1,27 @@
+/* SPDX-License-Identifier: Apache-2.0 */
+
+#include "BLI_tempfile.h"
+
+#include "BLI_fileops.h"
+#include "BLI_path_util.h"
+
+#include "testing/testing.h"
+
+namespace blender::tests {
+
+TEST(BLI_tempfile, BLI_temp_directory_path_get)
+{
+  char temp_dir[FILE_MAX];
+  BLI_temp_directory_path_get(temp_dir, sizeof(temp_dir));
+
+  ASSERT_STRNE(temp_dir, "");
+
+  EXPECT_EQ(temp_dir[strlen(temp_dir) - 1], SEP);
+
+  EXPECT_TRUE(BLI_exists(temp_dir));
+  EXPECT_TRUE(BLI_is_dir(temp_dir));
+
+  EXPECT_TRUE(BLI_path_is_abs_from_cwd(temp_dir));
+}
+
+}  // namespace blender::tests