Cannot link shared library

[moritzbuhl]

On OpenBSD I cannot build v5.9:

/usr/bin/libtool --mode=link cc -O2 -pipe -g -DNETSNMP_ENABLE_IPV6 -fno-strict-aliasing -DNETSNMP_REMOVE_U64 -O2 -pipe -g -Uopenbsd6 -Dopen
-checks -pipe -fstack-protector-strong -I/usr/local/include  -I/usr/libdata/perl5/amd64-openbsd/CORE   -Wall -Wextra -Wstrict-prototypes -W
no-type-limits -rpath /usr/local/lib -o libnetsnmp.la snmp_client.lo mib.lo parse.lo snmp_api.lo snmp.lo         snmp_auth.lo asn1.lo md5.l
tools.lo  snmp_logging.lo        text_utils.lo   large_fd_set.lo cert_util.lo snmp_openssl.lo            snmpv3.lo lcd_time.lo keytools.lo 
.lo fd_event_manager.lo          check_varbind.lo                                        mt_support.lo snmp_enum.lo snmp-tc.lo snmp_service
snmpIPv6BaseDomain.lo transports/snmpIPBaseDomain.lo transports/snmpUDPBaseDomain.lo transports/snmpUDPIPv4BaseDomain.lo transports/snmpTCP
IPv6Domain.lo transports/snmpTCPIPv6Domain.lo transports/snmpUDPDomain.lo transports/snmpTCPDomain.lo transports/snmpAliasDomain.lo transpo
 snmp_version.lo      container.lo container_binary_array.lo                     ucd_compat.lo                                            d
iner_iterator.lo  -Wl,-no-undefined  -lm   -lcrypto                                                                                        
libtool: link: cc -shared -fPIC -DPIC -o .libs/libnetsnmp.so.17.1 -O2 -pipe -g -DNETSNMP_ENABLE_IPV6 -fno-strict-aliasing -DNETSNMP_REMOVE_
aliasing -fno-delete-null-pointer-checks -pipe -fstack-protector-strong -I/usr/local/include -I/usr/libdata/perl5/amd64-openbsd/CORE -Wall 
mpare -Wno-unused-parameter -Wno-type-limits -Wl,-no-undefined .libs/snmp_client.o .libs/mib.o .libs/parse.o .libs/snmp_api.o .libs/snmp.o 
/int64.o .libs/read_config.o .libs/pkcs.o .libs/snmp_debug.o .libs/tools.o .libs/snmp_logging.o .libs/text_utils.o .libs/large_fd_set.o .li
libs/callback.o .libs/default_store.o .libs/snmp_alarm.o .libs/data_list.o .libs/oid_stash.o .libs/fd_event_manager.o .libs/check_varbind.o
printf.o .libs/snmp_transport.o transports/.libs/snmpIPv6BaseDomain.o transports/.libs/snmpIPBaseDomain.o transports/.libs/snmpUDPBaseDomai
nmpSocketBaseDomain.o transports/.libs/snmpIPv4BaseDomain.o transports/.libs/snmpUDPIPv6Domain.o transports/.libs/snmpTCPIPv6Domain.o trans
sports/.libs/snmpUnixDomain.o transports/.libs/snmpCallbackDomain.o .libs/snmp_secmod.o .libs/snmpusm.o .libs/snmp_version.o .libs/containe
tainer_null.o .libs/container_list_ssll.o .libs/container_iterator.o -L.libs -lm -lcrypto -Wl,-soname,libnetsnmp.so.17.1                   
ld: error: undefined symbol: calloc                                  
>>> referenced by snmp_client.c:130                                                                                                        
>>>               .libs/snmp_client.o:(snmp_pdu_create)              
>>> referenced by snmp_client.c:130                                                                                                        
>>>               .libs/snmp_client.o:(_query)                                                                                             
>>> referenced by mib.c:3179                                                                                                               
>>>               .libs/mib.o:(netsnmp_sprint_realloc_objid_tree)                                                                          
>>> referenced by mib.c:2871                                                                                                               
>>>               .libs/mib.o:(netsnmp_init_mib)                     
>>> referenced by mib.c:3108                                                                                                               
>>>               .libs/mib.o:(netsnmp_sprint_realloc_objid)                                                                               
>>> referenced by mib.c:3347                                    

Bisecting between 5.8.1.pre2 and 5.8.1.rc1 showed that commit cb9b87d is at fault.
After some testing I am convinced that -lc is missing:

Here is a small POC:

scanny$ cat Makefile hello.c  

LDFLAGS =       -Wl,-no-undefined
CFLAGS =        -shared

#include <stdio.h>
int
main(void){
        printf("hello world\n");
        return 0;
}
scanny$ make hello
cc -shared  -Wl,-no-undefined -o hello hello.c 
ld: error: undefined symbol: printf
>>> referenced by hello.c
>>>               /tmp/hello-9a4a5e.o:(main)
cc: error: linker command failed with exit code 1 (use -v to see invocation)
*** Error 1 in /tmp/tmp.JZ1T2Ayofw (<sys.mk>:85 'hello')

After addding -lc:

scanny$ cat Makefile hello.c                                                                                                              

LDFLAGS =       -lc -Wl,-no-undefined
CFLAGS =        -shared

#include <stdio.h>
int
main(void){
        printf("hello world\n");
        return 0;
}
scanny$ make hello
cc -shared  -lc -Wl,-no-undefined -o hello hello.c 

So the solution should be adding -lc somewhere in the linker flags.

[bvanassche]

In the libtool source code I found the following:

	  *-*-openbsd* | *-*-freebsd* | *-*-dragonfly*)
	    # Do not include libc due to us having libc/libc_r.
	    ;;

How to decide whether to link libnetsnmp against libc or libc_r?

[sthen]

I think it would be better to avoid -Wl,-no-undefined on OpenBSD. I'm not sure of the original reason but shared libraries are explicitly not recording a dependency on libc and I think that's what trips up the -no-undefined check.

[bvanassche]

Please take a look at commit ee7c66c.

[sthen]

@bvanassche Sorry for the slow reply, confirmed your commit is working on OpenBSD.

[bvanassche]

Thanks for confirming!