dhcp: Fix compiler error

[thomas]

(Reported by Clayton J. on blfs-dev)

Instructions in book leads to errors like

discover.c:646:4: error: 'strncpy' output may be truncated copying 15 bytes from a string of length 15 [-Werror=stringop-truncation]
    strncpy(tmp->name, info.name, sizeof(tmp->name) - 1);

This is caused by a strange handling of set/unset CFLAGS. Doing an

export CFLAGS="-D...

makes it compile. Most likely it has been missed because we might had CFLAGS exported while testing. With this export of CFLAGS, our -D's are recognized but but -fno-strict-aliasing gets not set but it would be if CFLAGS are not spezified.

Remove the -Werror flag by doing a

sed -e "/STD_CWARNINGS=/ s/-Werror//" -i configure

This would make it compile too but the CFLAGS we set (without the export) will not be used. See summary of configure script.

I'd propose to solve it like this:

export CFLAGS="$CFLAGS -Wall -fno-strict-aliasing \
        -D_PATH_DHCLIENT_SCRIPT='\"/sbin/dhclient-script\"' \
        -D_PATH_DHCPD_CONF='\"/etc/dhcp/dhcpd.conf\"' \
        -D_PATH_DHCLIENT_CONF='\"/etc/dhcp/dhclient.conf\"'"
./configure --prefix=/usr                                           \
            --sysconfdir=/etc/dhcp                                  \
            --localstatedir=/var                                    \
            --with-srv-lease-file=/var/lib/dhcpd/dhcpd.leases       \
            --with-srv6-lease-file=/var/lib/dhcpd/dhcpd6.leases     \
            --with-cli-lease-file=/var/lib/dhclient/dhclient.leases \
            --with-cli6-lease-file=/var/lib/dhclient/dhclient6.leases

The summary of configure than looks like (note the CFLAGS line):

     ISC DHCP source configure results:
    -=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-

Package:
  Name:          DHCP
  Version:       4.4.1

C Compiler:      gcc

Flags:
  DEFS:          -DHAVE_CONFIG_H
  CFLAGS:         -Wall -fno-strict-aliasing         -D_PATH_DHCLIENT_SCRIPT='"/sbin/dhclient-script"'         -D_PATH_DHCPD_CONF='"/etc/dhcp/dhcpd.conf"'         -D_PATH_DHCLIENT_CONF='"/etc/dhcp/dhclient.conf"'  -I$(top_srcdir)/includes -I/home/lfs/dhcp-4.4.1/bind/include

DHCP versions:   DHCPv4 and DHCPv6

Features:
  debug:         no
  failover:      yes
  execute:       yes
  binary-leases: no
  dhcpv6:        yes
  delayed-ack:   yes
  dhcpv4o6:      no
  relay-port:    no

Developer:
  ATF unittests : no


Now you can type make to build ISC DHCP

Please add comments!

[Bruce Dubbs]

One thing to keep in mind is that we need to see if CFLAGS is already set and if it is, save it and restore it after the package has been installed,

[thomas]

Fixed in r20561 by exporting modified CFLAGS in a subshell. The subshell saves CFLAGS if they are allready set in environment.