pgsql-bugs(at)postgresql(dot)org writes:
> stringinfo.c:115: `va_list' undeclared (first use in this function)
Try changing src/include/c.h so that <stddef.h> and <stdarg.h> are
included unconditionally (near line 53) and remove #include <varargs.h>
near line 770.
Or try 7.1RC2 or later --- these changes are already made for 7.1.
regards, tom lane