pneubeck pointed out an obvious thing, that a second p = stext + strlen(stext) - 1 is unnecessary

main.c

@@ -273,7 +273,7 @@ main(int argc, char *argv[]) {
 				break;
 			default:
 				for(stext[r] = '\0', p = stext + strlen(stext) - 1; p >= stext && *p == '\n'; *p-- = '\0');
-				for(p = stext + strlen(stext) - 1; p >= stext && *p != '\n'; --p);
+				for(; p >= stext && *p != '\n'; --p);
 				if(p > stext)
 					strncpy(stext, p + 1, sizeof stext);
 			}