lib: path-util - Allocate more space earlier

Fixes assert crash in path_normalize when termination
needs to happen at asize boundary.

Panic: file path-util.c: line 93 (path_normalize): assertion failed: ((size_t)((npath_pos - npath) + 1) < asize)

src/lib/path-util.c

@@ -87,13 +87,6 @@ static int path_normalize(const char *path, bool resolve_links,
 				for (; *(npath_pos-1) != '/'; npath_pos--);
 			}
 		} else {
-			/* make sure npath now ends in slash */
-			if (*(npath_pos-1) != '/') {
-				i_assert(npath_pos >= npath);
-				i_assert((size_t)((npath_pos - npath) + 1) < asize);
-				*(npath_pos++) = '/';
-			}
-
 			/* allocate space if necessary */
 			if ((npath_pos + seglen + 1) >= (npath + asize)) {
 				ptrdiff_t npath_offset = npath_pos - npath;
@@ -102,6 +95,13 @@ static int path_normalize(const char *path, bool resolve_links,
 				npath_pos = npath + npath_offset;
 			}
 
+			/* make sure npath now ends in slash */
+			if (*(npath_pos-1) != '/') {
+				i_assert(npath_pos >= npath);
+				i_assert((size_t)((npath_pos - npath) + 1) < asize);
+				*(npath_pos++) = '/';
+			}
+
 			/* copy segment to normalized path */
 			i_assert(npath_pos >= npath);
 			i_assert((size_t)((npath_pos - npath) + seglen) < asize);