+Valgrind <http://valgrind.org/> is also highly recommended, if
+Valgrind supports your architecture.
+
+Bison is written using Bison grammars, so there are bootstrapping
+issues. The bootstrap script attempts to discover when the C code
+generated from the grammars is out of date, and to bootstrap with an
+out-of-date version of the C code, but the process is not foolproof.
+Also, you may run into similar problems yourself if you modify Bison.