According to Gordon Atwood <gordon@cs.ualberta.ca>, GNU C on SunOS

4.1.4 uses libiberty to define strtoul and strerror.

Configure

@@ -163,7 +163,7 @@ my %table=(
 
 # Sunos configs, assuming sparc for the gcc one.
 ##"sunos-cc", "cc:-O4 -DNOPROTO -DNOCONST::(unknown)::DES_UNROLL:::",
-"sunos-gcc","gcc:-O3 -mv8 -Dssize_t=int::(unknown)::BN_LLONG RC4_CHAR RC4_CHUNK DES_UNROLL DES_PTR DES_RISC1:::",
+"sunos-gcc","gcc:-O3 -mv8 -Dssize_t=int::(unknown):-liberty:BN_LLONG RC4_CHAR RC4_CHUNK DES_UNROLL DES_PTR DES_RISC1:::",
 
 #### IRIX 5.x configs
 # -mips2 flag is added by ./config when appropriate.