-string_datestamp_offset = -1; /* Datestamp not inserted */
-string_datestamp_length = 0; /* Datestamp not inserted */
-string_datestamp_type = 0; /* Datestamp not inserted */
+int width, precision, off, lim, need;
+const char * fp = format; /* Deliberately not unsigned */
+BOOL dest_tainted = FALSE;
+
+string_datestamp_offset = -1; /* Datestamp not inserted */
+string_datestamp_length = 0; /* Datestamp not inserted */
+string_datestamp_type = 0; /* Datestamp not inserted */
+
+#ifdef COMPILE_UTILITY
+assert(!(flags & SVFMT_EXTEND));
+assert(g);
+#else
+
+/* Ensure we have a string, to save on checking later */
+if (!g) g = string_get(16);
+else if (!(flags & SVFMT_TAINT_NOCHK)) dest_tainted = is_tainted(g->s);
+
+if (!(flags & SVFMT_TAINT_NOCHK) && !dest_tainted && is_tainted(format))
+ {
+#ifndef MACRO_PREDEF
+ if (!(flags & SVFMT_REBUFFER))
+ die_tainted(US"string_vformat", func, line);
+#endif
+ gstring_rebuffer(g);
+ dest_tainted = TRUE;
+ }
+#endif /*!COMPILE_UTILITY*/
+
+lim = g->size - 1; /* leave one for a nul */
+off = g->ptr; /* remember initial offset in gstring */