7.0 installation problem, help please :-(

I'm pgsql newbie. I try to install the pgsql 7.0 on my Solaris 8 x86 server
but fail. The following is the error message:

stringinfo.c: In function `appendStringInfo':
stringinfo.c:104: `va_list' undeclared (first use in this function)
stringinfo.c:104: (Each undeclared identifier is reported only once
stringinfo.c:104: for each function it appears in.)
stringinfo.c:104: parse error before `args'
stringinfo.c:121: warning: implicit declaration of function `va_start'
stringinfo.c:121: `args' undeclared (first use in this function)
stringinfo.c:124: warning: implicit declaration of function `va_end'
gmake[2]: *** [stringinfo.o] Error 1
gmake[2]: Leaving directory `/usr/share/src/postgresql-7.0/src/backend/lib'
gmake[1]: *** [lib.dir] Error 2
gmake[1]: Leaving directory `/usr/share/src/postgresql-7.0/src/backend'
gmake: *** [all] Error 2

The installed softwares on the Solaris 8
1. gcc 2.95.2
2. bison 1.28
3. flex 2.5.4
4. gmake, zcat ...etc.

Can anyone help me? 1,000,000 thanks

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Chris Chan