add api function BLI_path_append to add to a path (and ensure a seperator), replaces BLI_join_dirfile when the dir and the destimation were the same.

source/blender/blenlib/BLI_path_util.h

@@ -89,7 +89,18 @@ void BLI_make_existing_file(const char *name);
 void BLI_split_dirfile(const char *string, char *dir, char *file, const size_t dirlen, const size_t filelen);
 void BLI_split_dir_part(const char *string, char *dir, const size_t dirlen);
 void BLI_split_file_part(const char *string, char *file, const size_t filelen);
-void BLI_join_dirfile(char *string, const size_t maxlen, const char *dir, const char *file);
+void BLI_path_append(char *__restrict dst, const size_t maxlen,
+                     const char *__restrict file)
+#ifdef __GNUC__
+__attribute__((nonnull))
+#endif
+;
+void BLI_join_dirfile(char *__restrict string, const size_t maxlen,
+                      const char *__restrict dir, const char *__restrict file)
+#ifdef __GNUC__
+__attribute__((nonnull))
+#endif
+;
 const char *BLI_path_basename(const char *path);
 
 typedef enum bli_rebase_state {

source/blender/blenlib/intern/fileops.c

@@ -445,7 +445,7 @@ static void join_dirfile_alloc(char **dst, size_t *alloc_len, const char *dir, c
 	size_t len = strlen(dir) + strlen(file) + 1;
 
 	if (*dst == NULL)
-		*dst = MEM_callocN(len + 1, "join_dirfile_alloc path");
+		*dst = MEM_mallocN(len + 1, "join_dirfile_alloc path");
 	else if (*alloc_len < len)
 		*dst = MEM_reallocN(*dst, len + 1);
 

source/blender/blenlib/intern/path_util.c

@@ -1690,6 +1690,26 @@ void BLI_split_file_part(const char *string, char *file, const size_t filelen)
 	BLI_split_dirfile(string, NULL, file, 0, filelen);
 }
 
+/**
+ * Append a filename to a dir, ensuring slash separates.
+ */
+void BLI_path_append(char *dst, const size_t maxlen, const char *file)
+{
+	size_t dirlen = BLI_strnlen(dst, maxlen);
+
+	/* inline BLI_add_slash */
+	if ((dirlen > 0) && (dst[dirlen - 1] != SEP)) {
+		dst[dirlen++] = SEP;
+		dst[dirlen] = '\0';
+	}
+
+	if (dirlen >= maxlen) {
+		return; /* fills the path */
+	}
+
+	BLI_strncpy(dst + dirlen, file, maxlen - dirlen);
+}
+
 /**
  * Simple appending of filename to dir, does not check for valid path!
  * Puts result into *dst, which may be same area as *dir.
@@ -1698,15 +1718,16 @@ void BLI_join_dirfile(char *dst, const size_t maxlen, const char *dir, const cha
 {
 	size_t dirlen = BLI_strnlen(dir, maxlen);
 
-	if (dst != dir) {
-		if (dirlen == maxlen) {
-			memcpy(dst, dir, dirlen);
-			dst[dirlen - 1] = '\0';
-			return; /* dir fills the path */
-		}
-		else {
-			memcpy(dst, dir, dirlen + 1);
-		}
+	/* args can't match */
+	BLI_assert(!ELEM(dst, dir, file));
+
+	if (dirlen == maxlen) {
+		memcpy(dst, dir, dirlen);
+		dst[dirlen - 1] = '\0';
+		return; /* dir fills the path */
+	}
+	else {
+		memcpy(dst, dir, dirlen + 1);
 	}
 
 	if (dirlen + 1 >= maxlen) {
@@ -1723,10 +1744,6 @@ void BLI_join_dirfile(char *dst, const size_t maxlen, const char *dir, const cha
 		return; /* fills the path */
 	}
 
-	if (file == NULL) {
-		return;
-	}
-
 	BLI_strncpy(dst + dirlen, file, maxlen - dirlen);
 }
 
@@ -1842,7 +1859,7 @@ int BLI_rebase_path(char *abs, size_t abs_len,
 			/* subdirectories relative to blend_dir */
 			BLI_join_dirfile(dest_path, sizeof(dest_path), dest_dir, rel_dir);
 			/* same subdirectories relative to dest_dir */
-			BLI_join_dirfile(dest_path, sizeof(dest_path), dest_path, base);
+			BLI_path_append(dest_path, sizeof(dest_path), base);
 			/* keeping original item basename */
 		}
 
@@ -2063,7 +2080,7 @@ static void bli_where_am_i(char *fullname, const size_t maxlen, const char *name
 					else {
 						strncpy(filename, path, sizeof(filename));
 					}
-					BLI_join_dirfile(fullname, maxlen, fullname, name);
+					BLI_path_append(fullname, maxlen, name);
 					if (add_win32_extension(filename)) {
 						BLI_strncpy(fullname, filename, maxlen);
 						break;

source/blender/editors/interface/interface_ops.c

@@ -917,7 +917,7 @@ static void edittranslation_find_po_file(const char *root, const char *uilng, ch
 	/* First, full lang code. */
 	BLI_snprintf(tstr, sizeof(tstr), "%s.po", uilng);
 	BLI_join_dirfile(path, maxlen, root, uilng);
-	BLI_join_dirfile(path, maxlen, path, tstr);
+	BLI_path_append(path, maxlen, tstr);
 	if (BLI_is_file(path))
 		return;
 
@@ -941,7 +941,7 @@ static void edittranslation_find_po_file(const char *root, const char *uilng, ch
 
 			BLI_join_dirfile(path, maxlen, root, tstr);
 			strcat(tstr, ".po");
-			BLI_join_dirfile(path, maxlen, path, tstr);
+			BLI_path_append(path, maxlen, tstr);
 			if (BLI_is_file(path))
 				return;
 		}

source/blender/imbuf/intern/indexer.c

@@ -366,8 +366,8 @@ static void get_index_dir(struct anim *anim, char *index_dir, size_t index_dir_l
 	if (!anim->index_dir[0]) {
 		char fname[FILE_MAXFILE];
 		BLI_split_dirfile(anim->name, index_dir, fname, index_dir_len, sizeof(fname));
-		BLI_join_dirfile(index_dir, index_dir_len, index_dir, "BL_proxy");
-		BLI_join_dirfile(index_dir, index_dir_len, index_dir, fname);
+		BLI_path_append(index_dir, index_dir_len, "BL_proxy");
+		BLI_path_append(index_dir, index_dir_len, fname);
 	}
 	else {
 		BLI_strncpy(index_dir, anim->index_dir, index_dir_len);