Problems when making gdb

[Vallas, Nikolaos]

I have downloaded the gdb-5.1.tar.gz.
The system is an Compaq AlphaServer 800 running Tru64 Unix 4.0G
I have extracted the the file and i have run configure which went fine.
When i run the make command i receive the below errors.

# make
if [ x"" != x ]; then  cc -c -DHAVE_CONFIG_H -g -I.
-I/u01/gdb-5.1/libiberty/..i
cc -c -DHAVE_CONFIG_H -g -I. -I/u01/gdb-5.1/libiberty/../include   alloca.c
cc: Error: alloca.c, line 128: Missing ";". (nosemi)
     size_t size;
------------^
cc: Error: alloca.c, line 141: Invalid declarator. (declarator)
  {
--^
cc: Error: alloca.c, line 154: Invalid declarator. (declarator)
      else
------^
cc: Warning: alloca.c, line 127: In the declaration of "C_alloca", a
function d)
C_alloca (size);
^
cc: Error: alloca.c, line 131: In this declaration, a storage class of
"auto" o)
  register char *depth = ADDRESS_FUNCTION (probe);
--^
*** Exit 1
Stop.
# 

Could you tell what wrong?
I think the error is in the alloca.c lib file but my knowledge 
in C lang is not enough to find the error.
Thank you in advance.

Vallas Nikos.