Re: [PATCH]: Pass -no_pie on SYSTEMSPEC for darwin11

[IainS <developer@sandoe-acoustics.co.uk>]

Hi Mike, Jack,

On 17 Jun 2011, at 20:24, Jack Howarth wrote:

> On Fri, Jun 17, 2011 at 10:43:07AM -0700, Mike Stump wrote:
>> On Jun 16, 2011, at 7:21 PM, Jack Howarth wrote:
>>> The gcj compiler needs to pass -no_pie for linkage on darwin11 due  
>>> to the new -pie
>>> default of the linker. The attached patch accomplishes this by  
>>> passing -no_pie on SYSTEMSPEC
>>> for *-*-darwin[12]*. Since Darwin10 supports -no_pie in its  
>>> linker, I included it in the
>>> triplet match to simplify the syntax. Bootstrap and tested on  
>>> x86_64-apple-darwin11.
>>> Okay for gcc trunk?
>>
>> The darwin aspects of this seem right to me.  I'm less familiar  
>> with the SYSTEMSPEC bit in libjava, someone want to give a quick  
>> comment on if this is the right knob to twist?
>
>   Since SYSTEMSPEC in configure.ac is setting system specific  
> options for libgcj.spec.in, it seemed
> the most rational place to append -no_pie to (and we already had a  
> darwin entry in the case statement).
> FYI, I also tried a different approach of not appending -no_pie  
> SYSTEMSPEC on darwin but instead using...

maybe I need more coffee .. and the gcc gathering was very sociable...  
but...

... It seems to me that switching pie off in libjava spec == switching  
pie off for every java program.

(i.e. it doesn't seem equivalent to BOOT_CFLAGS, but maybe I'm still  
missing something).

>> Roughly, there are unresolved issues with position independent code  
>> with the garbage collector (or was it a problem with some unknown  
>> bit in the compiler), and this just turns off a new OS default for  
>> java to work around the issue.  I hope that's an at least half way  
>> accurate description.  We're aiming to have the default for C be - 
>> fpie, but for java, no pie.  For the C compiler, we must build the  
>> compiler without -pie in order for PCH to work.  It is reasonable  
>> to turn off pie in the java compiler as well.
>>
>> Jack, do we have a PR number for this?  If so, please include in  
>> the changelog in the usual spot.
>
> I plan on opening a PR shortly, but I was hoping to be able to  
> reproduce the same failures under linux
> using a bootstrap with the compiler defaulted to -fPIC code  
> generation and the inverse change applied
> to linux of...

The thing that is not clear is this.

libjava (and boehm-gc) with pie passes on d9 and d10 (modulo a test- 
suite related kludge); so it doesn't seem that there's a fundamental  
problem.
(c.f. PCH, which won't work with pie, by definition from its design).

AFAIR ecj1 is not involved in the libjava tests - because they don't  
actually compile from .java.

(I'm not debating that there is a problem with ecj1 - but maybe that  
needs to be solved in the explicit build instructions for that  
executable).

----

So is this 'fix' a work-around for a tool bug... or is there really a  
lurking problem in boehm-gc/libjava that is uncovered by darwin11?

we seem to be switching off pie without actually pointing at the  
reason for doing so...

Iain