2008/7/30 Jacob <jacobchappelle@xxxxxxxxx>:
> If we haven't beat this to death yet, the right way to fix these warnings
> is to return a "smth" data type... which most people have commented on
>
> // original version
> smth function()
> {
> switch (var) {
> case one:
> return 1;
> default:
> BUG();
> }
> }
>
> // modified version
> smth function()
> {
> smth ret = 0;
> switch (var) { // unless this is a global var is undefined
> case one:
> ret = 1; // 1 was not a 'smth' type so we should use
> the function's return type or face compiler errors/warnings
> break; // unless you want hard to find bugs always
> include a break;
> default:
> BUG(); // if this is a macro does it return a value?
> ret = 0;
> break;
> }
> return ret; // since we are returning a 'smth' type we do not
> let control reach the end of this non-void funtion
> }
Looks good, but how can I know which value should it return in that case?
>
>
> Where does this function get used, and what is it used for?
Ok, some examples
kernel/cpuset.c:
static u64 cpuset_read_u64(struct cgroup *cont, struct cftype *cft)
{
struct cpuset *cs = cgroup_cs(cont);
cpuset_filetype_t type = cft->private;
switch (type) {
case FILE_CPU_EXCLUSIVE:
return is_cpu_exclusive(cs);
case FILE_MEM_EXCLUSIVE:
return is_mem_exclusive(cs);
case FILE_MEM_HARDWALL:
return is_mem_hardwall(cs);
case FILE_SCHED_LOAD_BALANCE:
return is_sched_load_balance(cs);
case FILE_MEMORY_MIGRATE:
return is_memory_migrate(cs);
case FILE_MEMORY_PRESSURE_ENABLED:
return cpuset_memory_pressure_enabled;
case FILE_MEMORY_PRESSURE:
return fmeter_getrate(&cs->fmeter);
case FILE_SPREAD_PAGE:
return is_spread_page(cs);
case FILE_SPREAD_SLAB:
return is_spread_slab(cs);
default:
BUG();
}
}
static s64 cpuset_read_s64(struct cgroup *cont, struct cftype *cft)
{
struct cpuset *cs = cgroup_cs(cont);
cpuset_filetype_t type = cft->private;
switch (type) {
case FILE_SCHED_RELAX_DOMAIN_LEVEL:
return cs->relax_domain_level;
default:
BUG();
}
}
mm/mempolicy.c:
/*
* Depending on the memory policy provide a node from which to allocate the
* next slab entry.
* @policy must be protected by freeing by the caller. If @policy is
* the current task's mempolicy, this protection is implicit, as only the
* task can change it's policy. The system default policy requires no
* such protection.
*/
unsigned slab_node(struct mempolicy *policy)
{
if (!policy || policy->flags & MPOL_F_LOCAL)
return numa_node_id();
switch (policy->mode) {
case MPOL_PREFERRED:
/*
* handled MPOL_F_LOCAL above
*/
return policy->v.preferred_node;
case MPOL_INTERLEAVE:
return interleave_nodes(policy);
case MPOL_BIND: {
/*
* Follow bind policy behavior and start allocation at the
* first node.
*/
struct zonelist *zonelist;
struct zone *zone;
enum zone_type highest_zoneidx = gfp_zone(GFP_KERNEL);
zonelist = &NODE_DATA(numa_node_id())->node_zonelists[0];
(void)first_zones_zonelist(zonelist, highest_zoneidx,
&policy->v.nodes,
&zone);
return zone->node;
}
default:
BUG();
}
}
drivers/net/sky2.c:
/* Chip internal frequency for clock calculations */
static u32 sky2_mhz(const struct sky2_hw *hw)
{
switch (hw->chip_id) {
case CHIP_ID_YUKON_EC:
case CHIP_ID_YUKON_EC_U:
case CHIP_ID_YUKON_EX:
case CHIP_ID_YUKON_SUPR:
case CHIP_ID_YUKON_UL_2:
return 125;
case CHIP_ID_YUKON_FE:
return 100;
case CHIP_ID_YUKON_FE_P:
return 50;
case CHIP_ID_YUKON_XL:
return 156;
default:
BUG();
}
}
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