Re: [PATCH] MdeModulePkg:disable wraning to pass gcc4.8 build

["Gao, Liming" <liming.gao@intel.com>]

Laszlo:
   We meet with this failure in GCC4.8 and GCC4.9, but not in GCC5.  We don't verify earlier version than GCC4.8. 
   GCC48 is the specific tool chain for GCC4.8. But, GCC49 is the general tool chain that can be used with GCC4.9 or the above GCC version for LTO disable. So, even if we specify this warning for GCC48 and GCC49, it may be applied for GCC5 version. To be simplified, I suggest to disable this warning in the general style. I suggest to add more comments here to describe this warning for GCC4.8, GCC4.9 version. Not for GCC5. 
  
>>>> +  # Oniguruma: tag_end in parse_callout_of_name
>>>> +  GCC:*_*_*_CC_FLAGS = -Wno-error=maybe-uninitialized

Thanks
Liming
>-----Original Message-----
>From: edk2-devel [mailto:edk2-devel-bounces@lists.01.org] On Behalf Of
>Laszlo Ersek
>Sent: Tuesday, October 02, 2018 2:02 AM
>To: Tomas Pilar (tpilar) <tpilar@solarflare.com>; edk2-devel@lists.01.org
>Subject: Re: [edk2] [PATCH] MdeModulePkg:disable wraning to pass gcc4.8
>build
>
>Wait a sec:
>
>On 10/01/18 19:48, Laszlo Ersek wrote:
>
>> However, this (edk2) commit message seems to suggest that the warnings
>> are only present with gcc-4.8 (and no later gcc releases). This in turn
>> suggests that the warnings are spurious (presumably, later gcc releases
>> recognize that none of the affected variables are actually read without
>> a prior initialization or assignment.)
>>
>> Hence, upstream Oniguruma might argue that we should fix our compiler --
>> they might consider gcc-4.8 too old to care -- rather than litter their
>> code with superfluous assignments, just to pacify gcc-4.8.
>
>[...]
>
>> So, I think I agree with this patch, but the commit message should be a
>> *lot* more detailed. (Basically, include the analysis from above.)
>
>In fact, another improvement is possible: if the issue only affects
>gcc-4.8, then:
>
>>> On 29/09/18 02:55, Dongao Guo wrote:
>>>> Change-Id: I782962e4994a8edf14beb7ede8b1aabe233dc3a8
>>>> Contributed-under: TianoCore Contribution Agreement 1.1
>>>> ---
>>>>
>MdeModulePkg/Universal/RegularExpressionDxe/RegularExpressionDxe.inf |
>3 +++
>>>>  1 file changed, 3 insertions(+)
>>>>
>>>> diff --git
>a/MdeModulePkg/Universal/RegularExpressionDxe/RegularExpressionDxe.in
>f
>b/MdeModulePkg/Universal/RegularExpressionDxe/RegularExpressionDxe.in
>f
>>>> index 16e91bd..07bc02e 100644
>>>> ---
>a/MdeModulePkg/Universal/RegularExpressionDxe/RegularExpressionDxe.in
>f
>>>> +++
>b/MdeModulePkg/Universal/RegularExpressionDxe/RegularExpressionDxe.in
>f
>>>> @@ -109,3 +109,6 @@
>>>>
>>>>    # Oniguruma: error: variable 'fp' set but not used
>>>>    GCC:*_*_*_CC_FLAGS = -Wno-error=unused-but-set-variable
>>>> +
>>>> +  # Oniguruma: tag_end in parse_callout_of_name
>>>> +  GCC:*_*_*_CC_FLAGS = -Wno-error=maybe-uninitialized
>
>this toolchain glob pattern is too general. It should be:
>
>  GCC:*_GCC48_*_CC_FLAGS
>
>(or maybe spell it out for all GCC versions up to and including 4.8,
>from the earliest we support, 4.4.)
>
>Thanks
>Laszlo
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