EL 6 x86_64

4.8.0 on PPC further reveals:

fatal.c: In function 'print_fatal_info':
fatal.c:206:14: warning: unused variable 'uctx' [-Wunused-variable]
ucontext_t *uctx = (ucontext_t *)context;
^
fatal.c: At top level:
fatal.c:65:20: warning: 'get_register_name' defined but not used [-Wunused-function]
static const char *get_register_name(int reg)
^

The odbc.c warning is only there for 64 bit builds, I found.

Thanks, Volker, for reporting this!
The warning from odbc.c turned out to be a real error on 64-bit platform.
Can you test the solution from development branch svn://svn.zabbix.com/branches/dev/ZBX-6435 (trunk based)?
(PPC platform is also interesting)

Fixed in development branch svn://svn.zabbix.com/branches/dev/ZBX-6435 (trunk)

All gcc 4.8, Intel and PPC 32 and 64 bit architectures show two warnings for ZBX-6435:

lld_item.c: In function 'DBlld_update_items':
lld_item.c:609:2372: warning: 'item' may be used uninitialized in this function [-Wmaybe-uninitialized]
if (0 != strcmp(item->key_proto, key_proto))
^
lld_item.c:540:18: note: 'item' was declared here
zbx_lld_item_t *item;
^

...

checks_ipmi.c:836:3: warning: enumeration value 'IPMI_CHANGED' not handled in switch [-Wswitch]
switch (op)
^

Fixed in development branch svn://svn.zabbix.com/branches/dev/ZBX-6435 (trunk) rev. 34952

Successfully tested.

Fixed in version pre-2.1.0 rev. 35130

For the record: The latter two are still present in the Alpha release. Contrary to what I said above, the warning is also there with gcc 4.7.2.

lld_item.c: In function 'DBlld_update_items':
lld_item.c:609:23: warning: 'item' may be used uninitialized in this function [-Wmaybe-uninitialized]
if (0 != strcmp(item->key_proto, key_proto))
^

lld_item.c:540:18: note: 'item' was declared here
zbx_lld_item_t *item;
^
checks_ipmi.c: In function 'sensor_change':
checks_ipmi.c:836:3: warning: enumeration value 'IPMI_CHANGED' not handled in switch [-Wswitch]
switch (op)
^

No, forget that last comment, I was using the old tarball I made from SVN then.

4.7.2 and 4.8:

valuecache.c: In function 'zbx_vc_get_value_range':
valuecache.c:3379: warning: 'item' may be used uninitialized in this function
valuecache.c:3311: note: 'item' was declared here
mv -f .deps/libzbxdbcache_a-valuecache.Tpo .deps/libzbxdbcache_a-valuecache.Po
dbcache.c: In function 'DCmass_add_history':
dbcache.c:1809: warning: 'pvalue' may be used uninitialized in this function

EL6's gcc additionally warns about:

comms.c: In function 'zbx_tcp_check_security':
comms.c:1173: warning: dereferencing pointer 'name.87' does break strict-aliasing rules
comms.c:1173: note: initialized from here

modules.c: In function 'load_modules':
modules.c:123: warning: dereferencing type-punned pointer will break strict-aliasing rules
modules.c:139: warning: dereferencing type-punned pointer will break strict-aliasing rules
modules.c:156: warning: dereferencing type-punned pointer will break strict-aliasing rules
modules.c:165: warning: dereferencing type-punned pointer will break strict-aliasing rules
modules.c: In function 'unload_modules':
modules.c:237: warning: dereferencing type-punned pointer will break strict-aliasing rules
modules.c:237: warning: dereferencing pointer 'func_uninit.50' does break strict-aliasing rules
modules.c:237: note: initialized from here
modules.c: In function 'load_modules':
modules.c:123: warning: dereferencing pointer 'func_version.37' does break strict-aliasing rules
modules.c:123: note: initialized from here
modules.c:139: warning: dereferencing pointer 'func_init.40' does break strict-aliasing rules
modules.c:139: note: initialized from here
modules.c:156: warning: dereferencing pointer 'func_timeout.42' does break strict-aliasing rules
modules.c:156: note: initialized from here
modules.c:165: warning: dereferencing pointer 'func_list.44' does break strict-aliasing rules
modules.c:165: note: initialized from here

Complaints from EL5's gcc:

memalloc.c: In function '__zbx_mem_malloc':
memalloc.c:666: warning: comparison is always false due to limited range of data type
memalloc.c: In function '__zbx_mem_realloc':
memalloc.c:700: warning: comparison is always false due to limited range of data type

evalfunc.c: In function 'add_value_suffix_uptime':
evalfunc.c:1910: warning: implicit declaration of function 'round'
evalfunc.c:1910: warning: incompatible implicit declaration of built-in function 'round'
evalfunc.c: In function 'add_value_suffix_s':
evalfunc.c:1968: warning: incompatible implicit declaration of built-in function 'round'

httpmacro.c: In function 'httpmacro_append_pair':
httpmacro.c:168: warning: dereferencing type-punned pointer will break strict-aliasing rules

nodesync.c: In function 'node_sync':
nodesync.c:62: warning: 'rec' may be used uninitialized in this function

Thanks, fixed value cache related warnings (valuecache.c, dbcache.c) in ZBXNEXT-322 development branch