Re: [PATCH] arm/translate-a64: fix uninitialized variable warning

[Pan Nengyuan]

On 1/6/2020 10:15 AM, Richard Henderson wrote:
> On 1/6/20 11:57 AM, address@hidden wrote:
>> From: Pan Nengyuan <address@hidden>
>>
>> Fixes:
>> target/arm/translate-a64.c: In function 'disas_crypto_three_reg_sha512':
>> target/arm/translate-a64.c:13625:9: error: 'genfn' may be used uninitialized 
>> in this function [-Werror=maybe-uninitialized]
>>     genfn(tcg_rd_ptr, tcg_rn_ptr, tcg_rm_ptr);
>>     ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>> qemu/target/arm/translate-a64.c:13609:8: error: 'feature' may be used 
>> uninitialized in this function [-Werror=maybe-uninitialized]
>>     if (!feature) {
>>
>> Reported-by: Euler Robot <address@hidden>
>> Signed-off-by: Pan Nengyuan <address@hidden>
>> Cc: Peter Maydell <address@hidden> 
> 
> Are you compiling with reduced optimization?  The compiler should be able to
> prove that these variables are initialized.  It certainly does with -O2, on 
> all
> known gcc versions.

Yes, I compile it with optimization flags (-O2) and get this warnings. The gcc 
version is 8.2.1.

> 
> Perhaps a better fix is to add a
> 
>     default:
>         g_assert_not_reached();
> 
> entry to the o == 0 switch.  Though of course opcode must be in [0-3], based 
> on
> the extraction mask, so a default label isn't actually reachable.  But that's
> the only path I can see for which incomplete optimization would fail to prove
> initializatio
Yes, a default label is a better way.

> 
> r~
>