diff --git a/source/blender/blenkernel/intern/blender_undo.c b/source/blender/blenkernel/intern/blender_undo.c
index cd950e05415..9ccc53b6318 100644
--- a/source/blender/blenkernel/intern/blender_undo.c
+++ b/source/blender/blenkernel/intern/blender_undo.c
@@ -109,7 +109,7 @@ MemFileUndoData *BKE_memfile_undo_encode(Main *bmain, MemFileUndoData *mfu_prev)
     counter = counter % U.undosteps;
 
     BLI_snprintf(numstr, sizeof(numstr), "%d.blend", counter);
-    BLI_make_file_string("/", filename, BKE_tempdir_session(), numstr);
+    BLI_join_dirfile(filename, sizeof(filename), BKE_tempdir_session(), numstr);
 
     /* success = */ /* UNUSED */ BLO_write_file(bmain, filename, fileflags, NULL, NULL);
 
diff --git a/source/blender/editors/armature/pose_transform.c b/source/blender/editors/armature/pose_transform.c
index d366978ba2b..0360f385201 100644
--- a/source/blender/editors/armature/pose_transform.c
+++ b/source/blender/editors/armature/pose_transform.c
@@ -723,7 +723,7 @@ static int pose_copy_exec(bContext *C, wmOperator *op)
    * existing on it's own.
    */
   BKE_copybuffer_tag_ID(&ob_copy.id);
-  BLI_make_file_string("/", str, BKE_tempdir_base(), "copybuffer_pose.blend");
+  BLI_join_dirfile(str, sizeof(str), BKE_tempdir_base(), "copybuffer_pose.blend");
   BKE_copybuffer_save(temp_bmain, str, op->reports);
   /* We clear the lists so no datablocks gets freed,
    * This is required because objects in temp bmain shares same pointers
@@ -773,7 +773,7 @@ static int pose_paste_exec(bContext *C, wmOperator *op)
   /* Read copy buffer .blend file. */
   char str[FILE_MAX];
   Main *tmp_bmain = BKE_main_new();
-  BLI_make_file_string("/", str, BKE_tempdir_base(), "copybuffer_pose.blend");
+  BLI_join_dirfile(str, sizeof(str), BKE_tempdir_base(), "copybuffer_pose.blend");
   if (!BKE_copybuffer_read(tmp_bmain, str, op->reports, FILTER_ID_OB)) {
     BKE_report(op->reports, RPT_ERROR, "Copy buffer is empty");
     BKE_main_free(tmp_bmain);
diff --git a/source/blender/editors/space_file/file_ops.c b/source/blender/editors/space_file/file_ops.c
index e03d15d9f34..5004bb8dd77 100644
--- a/source/blender/editors/space_file/file_ops.c
+++ b/source/blender/editors/space_file/file_ops.c
@@ -948,8 +948,10 @@ static int bookmark_add_exec(bContext *C, wmOperator *UNUSED(op))
 
     fsmenu_insert_entry(
         fsmenu, FS_CATEGORY_BOOKMARKS, params->dir, NULL, ICON_FILE_FOLDER, FS_INSERT_SAVE);
-    BLI_make_file_string(
-        "/", name, BKE_appdir_folder_id_create(BLENDER_USER_CONFIG, NULL), BLENDER_BOOKMARK_FILE);
+    BLI_join_dirfile(name,
+                     sizeof(name),
+                     BKE_appdir_folder_id_create(BLENDER_USER_CONFIG, NULL),
+                     BLENDER_BOOKMARK_FILE);
     fsmenu_write_file(fsmenu, name);
   }
 
@@ -991,10 +993,10 @@ static int bookmark_delete_exec(bContext *C, wmOperator *op)
       char name[FILE_MAX];
 
       fsmenu_remove_entry(fsmenu, FS_CATEGORY_BOOKMARKS, index);
-      BLI_make_file_string("/",
-                           name,
-                           BKE_appdir_folder_id_create(BLENDER_USER_CONFIG, NULL),
-                           BLENDER_BOOKMARK_FILE);
+      BLI_join_dirfile(name,
+                       sizeof(name),
+                       BKE_appdir_folder_id_create(BLENDER_USER_CONFIG, NULL),
+                       BLENDER_BOOKMARK_FILE);
       fsmenu_write_file(fsmenu, name);
       ED_area_tag_refresh(sa);
       ED_area_tag_redraw(sa);
@@ -1045,8 +1047,10 @@ static int bookmark_cleanup_exec(bContext *C, wmOperator *UNUSED(op))
   if (changed) {
     char name[FILE_MAX];
 
-    BLI_make_file_string(
-        "/", name, BKE_appdir_folder_id_create(BLENDER_USER_CONFIG, NULL), BLENDER_BOOKMARK_FILE);
+    BLI_join_dirfile(name,
+                     sizeof(name),
+                     BKE_appdir_folder_id_create(BLENDER_USER_CONFIG, NULL),
+                     BLENDER_BOOKMARK_FILE);
     fsmenu_write_file(fsmenu, name);
     fsmenu_refresh_bookmarks_status(CTX_wm_manager(C), fsmenu);
     ED_area_tag_refresh(sa);
@@ -1122,8 +1126,10 @@ static int bookmark_move_exec(bContext *C, wmOperator *op)
   /* Need to update active bookmark number. */
   sfile->bookmarknr = new_index;
 
-  BLI_make_file_string(
-      "/", fname, BKE_appdir_folder_id_create(BLENDER_USER_CONFIG, NULL), BLENDER_BOOKMARK_FILE);
+  BLI_join_dirfile(fname,
+                   sizeof(fname),
+                   BKE_appdir_folder_id_create(BLENDER_USER_CONFIG, NULL),
+                   BLENDER_BOOKMARK_FILE);
   fsmenu_write_file(fsmenu, fname);
 
   ED_area_tag_redraw(sa);
@@ -1168,8 +1174,10 @@ static int reset_recent_exec(bContext *C, wmOperator *UNUSED(op))
   while (ED_fsmenu_get_entry(fsmenu, FS_CATEGORY_RECENT, 0) != NULL) {
     fsmenu_remove_entry(fsmenu, FS_CATEGORY_RECENT, 0);
   }
-  BLI_make_file_string(
-      "/", name, BKE_appdir_folder_id_create(BLENDER_USER_CONFIG, NULL), BLENDER_BOOKMARK_FILE);
+  BLI_join_dirfile(name,
+                   sizeof(name),
+                   BKE_appdir_folder_id_create(BLENDER_USER_CONFIG, NULL),
+                   BLENDER_BOOKMARK_FILE);
   fsmenu_write_file(fsmenu, name);
   ED_area_tag_redraw(sa);
 
@@ -1571,10 +1579,10 @@ int file_exec(bContext *C, wmOperator *exec_op)
                           FS_INSERT_SAVE | FS_INSERT_FIRST);
     }
 
-    BLI_make_file_string(BKE_main_blendfile_path(bmain),
-                         filepath,
-                         BKE_appdir_folder_id_create(BLENDER_USER_CONFIG, NULL),
-                         BLENDER_BOOKMARK_FILE);
+    BLI_join_dirfile(filepath,
+                     sizeof(filepath),
+                     BKE_appdir_folder_id_create(BLENDER_USER_CONFIG, NULL),
+                     BLENDER_BOOKMARK_FILE);
     fsmenu_write_file(ED_fsmenu_get(), filepath);
     WM_event_fileselect_event(wm, op, EVT_FILESELECT_EXEC);
   }
diff --git a/source/blender/editors/space_file/fsmenu.c b/source/blender/editors/space_file/fsmenu.c
index 017adfa22bb..4f3fc997074 100644
--- a/source/blender/editors/space_file/fsmenu.c
+++ b/source/blender/editors/space_file/fsmenu.c
@@ -267,10 +267,10 @@ void ED_fsmenu_entry_set_path(struct FSMenuEntry *fsentry, const char *path)
 
     fsentry->path = (path && path[0]) ? BLI_strdup(path) : NULL;
 
-    BLI_make_file_string("/",
-                         tmp_name,
-                         BKE_appdir_folder_id_create(BLENDER_USER_CONFIG, NULL),
-                         BLENDER_BOOKMARK_FILE);
+    BLI_join_dirfile(tmp_name,
+                     sizeof(tmp_name),
+                     BKE_appdir_folder_id_create(BLENDER_USER_CONFIG, NULL),
+                     BLENDER_BOOKMARK_FILE);
     fsmenu_write_file(ED_fsmenu_get(), tmp_name);
   }
 }
@@ -332,10 +332,10 @@ void ED_fsmenu_entry_set_name(struct FSMenuEntry *fsentry, const char *name)
       BLI_strncpy(fsentry->name, name, sizeof(fsentry->name));
     }
 
-    BLI_make_file_string("/",
-                         tmp_name,
-                         BKE_appdir_folder_id_create(BLENDER_USER_CONFIG, NULL),
-                         BLENDER_BOOKMARK_FILE);
+    BLI_join_dirfile(tmp_name,
+                     sizeof(tmp_name),
+                     BKE_appdir_folder_id_create(BLENDER_USER_CONFIG, NULL),
+                     BLENDER_BOOKMARK_FILE);
     fsmenu_write_file(ED_fsmenu_get(), tmp_name);
   }
 }
diff --git a/source/blender/editors/space_file/space_file.c b/source/blender/editors/space_file/space_file.c
index c7dee1c1680..11d759b5b75 100644
--- a/source/blender/editors/space_file/space_file.c
+++ b/source/blender/editors/space_file/space_file.c
@@ -802,7 +802,7 @@ void ED_file_read_bookmarks(void)
 
   if (cfgdir) {
     char name[FILE_MAX];
-    BLI_make_file_string("/", name, cfgdir, BLENDER_BOOKMARK_FILE);
+    BLI_join_dirfile(name, sizeof(name), cfgdir, BLENDER_BOOKMARK_FILE);
     fsmenu_read_bookmarks(ED_fsmenu_get(), name);
   }
 }
diff --git a/source/blender/editors/space_outliner/outliner_edit.c b/source/blender/editors/space_outliner/outliner_edit.c
index 945bfb55b1b..1d852d72e6e 100644
--- a/source/blender/editors/space_outliner/outliner_edit.c
+++ b/source/blender/editors/space_outliner/outliner_edit.c
@@ -770,7 +770,7 @@ static int outliner_id_copy_exec(bContext *C, wmOperator *op)
     return OPERATOR_CANCELLED;
   }
 
-  BLI_make_file_string("/", str, BKE_tempdir_base(), "copybuffer.blend");
+  BLI_join_dirfile(str, sizeof(str), BKE_tempdir_base(), "copybuffer.blend");
   BKE_copybuffer_save(bmain, str, op->reports);
 
   BKE_reportf(op->reports, RPT_INFO, "Copied %d selected data-block(s)", num_ids);
@@ -797,7 +797,7 @@ static int outliner_id_paste_exec(bContext *C, wmOperator *op)
   char str[FILE_MAX];
   const short flag = FILE_AUTOSELECT | FILE_ACTIVE_COLLECTION;
 
-  BLI_make_file_string("/", str, BKE_tempdir_base(), "copybuffer.blend");
+  BLI_join_dirfile(str, sizeof(str), BKE_tempdir_base(), "copybuffer.blend");
 
   const int num_pasted = BKE_copybuffer_paste(C, str, flag, op->reports, 0);
   if (num_pasted == 0) {
diff --git a/source/blender/editors/space_view3d/view3d_ops.c b/source/blender/editors/space_view3d/view3d_ops.c
index cfdd3dcbb6f..be8824971cb 100644
--- a/source/blender/editors/space_view3d/view3d_ops.c
+++ b/source/blender/editors/space_view3d/view3d_ops.c
@@ -76,7 +76,7 @@ static int view3d_copybuffer_exec(bContext *C, wmOperator *op)
   }
   CTX_DATA_END;
 
-  BLI_make_file_string("/", str, BKE_tempdir_base(), "copybuffer.blend");
+  BLI_join_dirfile(str, sizeof(str), BKE_tempdir_base(), "copybuffer.blend");
   BKE_copybuffer_save(bmain, str, op->reports);
 
   BKE_reportf(op->reports, RPT_INFO, "Copied %d selected object(s)", num_copied);
@@ -108,7 +108,7 @@ static int view3d_pastebuffer_exec(bContext *C, wmOperator *op)
     flag |= FILE_ACTIVE_COLLECTION;
   }
 
-  BLI_make_file_string("/", str, BKE_tempdir_base(), "copybuffer.blend");
+  BLI_join_dirfile(str, sizeof(str), BKE_tempdir_base(), "copybuffer.blend");
 
   const int num_pasted = BKE_copybuffer_paste(C, str, flag, op->reports, FILTER_ID_OB);
   if (num_pasted == 0) {
diff --git a/source/blender/io/collada/DocumentExporter.cpp b/source/blender/io/collada/DocumentExporter.cpp
index 24a960ab287..9d61b9b56ab 100644
--- a/source/blender/io/collada/DocumentExporter.cpp
+++ b/source/blender/io/collada/DocumentExporter.cpp
@@ -157,13 +157,12 @@ DocumentExporter::DocumentExporter(BlenderContext &blender_context, ExportSettin
 static COLLADABU::NativeString make_temp_filepath(const char *name, const char *extension)
 {
   char tempfile[FILE_MAX];
-  const char *tempdir = BKE_tempdir_session();
 
   if (name == NULL) {
     name = "untitled";
   }
 
-  BLI_make_file_string(NULL, tempfile, tempdir, name);
+  BLI_join_dirfile(tempfile, sizeof(tempfile), BKE_tempdir_session(), name);
 
   if (extension) {
     BLI_path_extension_ensure(tempfile, FILE_MAX, extension);
diff --git a/source/blender/render/intern/source/render_result.c b/source/blender/render/intern/source/render_result.c
index 81395399134..2021967b05d 100644
--- a/source/blender/render/intern/source/render_result.c
+++ b/source/blender/render/intern/source/render_result.c
@@ -1335,7 +1335,7 @@ void render_result_exr_file_path(Scene *scene, const char *layname, int sample,
   /* Make name safe for paths, see T43275. */
   BLI_filename_make_safe(name);
 
-  BLI_make_file_string("/", filepath, BKE_tempdir_session(), name);
+  BLI_join_dirfile(filepath, FILE_MAX, BKE_tempdir_session(), name);
 }
 
 /* called for reading temp files, and for external engines */
diff --git a/source/blender/windowmanager/intern/wm_files.c b/source/blender/windowmanager/intern/wm_files.c
index 1ce56ad2dfc..83355ecb786 100644
--- a/source/blender/windowmanager/intern/wm_files.c
+++ b/source/blender/windowmanager/intern/wm_files.c
@@ -1088,7 +1088,7 @@ void wm_history_file_read(void)
     return;
   }
 
-  BLI_make_file_string("/", name, cfgdir, BLENDER_HISTORY_FILE);
+  BLI_join_dirfile(name, sizeof(name), cfgdir, BLENDER_HISTORY_FILE);
 
   lines = BLI_file_read_as_lines(name);
 
@@ -1144,7 +1144,7 @@ static void wm_history_file_write(void)
     return;
   }
 
-  BLI_make_file_string("/", name, user_config_dir, BLENDER_HISTORY_FILE);
+  BLI_join_dirfile(name, sizeof(name), user_config_dir, BLENDER_HISTORY_FILE);
 
   fp = BLI_fopen(name, "w");
   if (fp) {
@@ -1487,7 +1487,7 @@ void wm_autosave_location(char *filepath)
   }
 #endif
 
-  BLI_make_file_string("/", filepath, BKE_tempdir_base(), path);
+  BLI_join_dirfile(filepath, FILE_MAX, BKE_tempdir_base(), path);
 }
 
 void WM_autosave_init(wmWindowManager *wm)
@@ -1559,7 +1559,7 @@ void wm_autosave_delete(void)
 
   if (BLI_exists(filename)) {
     char str[FILE_MAX];
-    BLI_make_file_string("/", str, BKE_tempdir_base(), BLENDER_QUIT_FILE);
+    BLI_join_dirfile(str, sizeof(str), BKE_tempdir_base(), BLENDER_QUIT_FILE);
 
     /* if global undo; remove tempsave, otherwise rename */
     if (U.uiflag & USER_GLOBALUNDO) {
@@ -2439,7 +2439,7 @@ void WM_recover_last_session(bContext *C, ReportList *reports)
 {
   char filepath[FILE_MAX];
 
-  BLI_make_file_string("/", filepath, BKE_tempdir_base(), BLENDER_QUIT_FILE);
+  BLI_join_dirfile(filepath, sizeof(filepath), BKE_tempdir_base(), BLENDER_QUIT_FILE);
   /* if reports==NULL, it's called directly without operator, we add a quick check here */
   if (reports || BLI_exists(filepath)) {
     G.fileflags |= G_FILE_RECOVER;
diff --git a/source/blender/windowmanager/intern/wm_init_exit.c b/source/blender/windowmanager/intern/wm_init_exit.c
index 7a05ef4b849..c428eefb028 100644
--- a/source/blender/windowmanager/intern/wm_init_exit.c
+++ b/source/blender/windowmanager/intern/wm_init_exit.c
@@ -358,7 +358,8 @@ void WM_init(bContext *C, int argc, const char **argv)
   /* allow a path of "", this is what happens when making a new file */
 #if 0
   if (BKE_main_blendfile_path_from_global()[0] == '\0') {
-    BLI_make_file_string("/", G_MAIN->name, BKE_appdir_folder_default(), "untitled.blend");
+    BLI_join_dirfile(
+        G_MAIN->name, sizeof(G_MAIN->name), BKE_appdir_folder_default(), "untitled.blend");
   }
 #endif
 
@@ -495,7 +496,7 @@ void WM_exit_ex(bContext *C, const bool do_python)
         bool has_edited;
         int fileflags = G.fileflags & ~(G_FILE_COMPRESS | G_FILE_HISTORY);
 
-        BLI_make_file_string("/", filename, BKE_tempdir_base(), BLENDER_QUIT_FILE);
+        BLI_join_dirfile(filename, sizeof(filename), BKE_tempdir_base(), BLENDER_QUIT_FILE);
 
         has_edited = ED_editors_flush_edits(bmain);
 
diff --git a/source/blender/windowmanager/intern/wm_platform_support.c b/source/blender/windowmanager/intern/wm_platform_support.c
index 94eceafc59b..73ba4b550c9 100644
--- a/source/blender/windowmanager/intern/wm_platform_support.c
+++ b/source/blender/windowmanager/intern/wm_platform_support.c
@@ -55,7 +55,7 @@ static bool wm_platform_support_check_approval(const char *platform_support_key,
 
   if (cfgdir) {
     char filepath[FILE_MAX];
-    BLI_make_file_string("/", filepath, cfgdir, BLENDER_PLATFORM_SUPPORT_FILE);
+    BLI_join_dirfile(filepath, sizeof(filepath), cfgdir, BLENDER_PLATFORM_SUPPORT_FILE);
     LinkNode *lines = BLI_file_read_as_lines(filepath);
     for (LinkNode *line_node = lines; line_node; line_node = line_node->next) {
       char *line = line_node->link;
diff --git a/source/creator/creator_signals.c b/source/creator/creator_signals.c
index afec54a636c..dff23837203 100644
--- a/source/creator/creator_signals.c
+++ b/source/creator/creator_signals.c
@@ -114,7 +114,7 @@ static void sig_handle_crash(int signum)
       char fname[FILE_MAX];
 
       if (!(G_MAIN && G_MAIN->name[0])) {
-        BLI_make_file_string("/", fname, BKE_tempdir_base(), "crash.blend");
+        BLI_join_dirfile(fname, sizeof(fname), BKE_tempdir_base(), "crash.blend");
       }
       else {
         BLI_strncpy(fname, G_MAIN->name, sizeof(fname));