> If the driver can be sure that an executable is being compiled
> (which is a challenge in general case, but simple cases --
> compilation of GCC testsuites -- can be accommodated)
I totally agree here that it could be a challenge. Also it could be
quite confusing: if the user wants to get assembler code we must
conservatively generate it with -fpic; However producing executable
with default options and then objdumping it will give us different
assembly with -fno-pic..
And although it could fix those testcases that are failing right now
on android that would indeed be hiding our head in the sand.
Considering all that, I believe that we are left with only one
solution: to carefully add "-fno-pic" or
"{ target nonpic }" to the affected tests as we discussed above.
Thank you very much for your help!
2012/11/18 Maxim Kuvyrkov <ma...@codesourcery.com>:
> On 18/11/2012, at 7:50 AM, Alexander Ivchenko wrote:
>
>> You are right, we are talking about the same things. The only open
>> question I see is regarding:
>>
>>>>>> In other cases we can safely assume
>>>>>> that the executable will be created and
>>>>>> in such case it would be a good idea to use -fPIE.
>>
>>>> I don't see why it would be a good idea to use -fPIE for most normal
>>>> user-space applications when -fno-pic would
>>>> suffice and provide better code.
>>
>> Do you agree that if the driver knows that the executable will be at
>> the end of the build
>> we can safely use -fno-pic or -fPIE to override -fpic default?
>
> If the driver can be sure that an executable is being compiled (which is a
> challenge in general case, but simple cases -- compilation of GCC testsuites
> -- can be accommodated) then it is OK to revert to default for a particular
> <arch>-linux-gnu target. For most architectures that would mean reverting to
> -fno-pic, but at least mips-linux-gnu uses -fpic by default in certain
> configurations. This is me not picking on your proposal, just alerting that
> -fno-pic may not be the right choice for executables for all targets.
>
>> I'm not
>> quite sure which one is better for Android; -fPIE will
>> give us all the security advantages of the position independent code
>> and probably is a better option.
>
> Using -fPIE will also bring all the performance drawbacks of PIC, there is a
> reason why -fPIE is not the most common way of building applications. I
> don't think Android is too security-concious a platform to warrant -fPIE
> (does Android even use address-space randomization?). Performance is a more
> serious consideration for its target market.
>
> Alexander, I appreciate you looking into -fpic vs -fno-pic compilation for
> Android.
>
> Thank you,
>
> --
> Maxim Kuvyrkov
> CodeSourcery / Mentor Graphics
>
