[sword-devel] Segmentation fault - was Re: SWORD 1.7.0RC3

[Troy A. Griffitts]

Just committed a large delta which checks for all file local globals and 
uses Jaaks suggested method for initializing these to avoid global 
initializer order conflicts.

The commit looks large, but it is a very regular change, there are some 
whitespace changes as well when I saw code that didn't conform to our 
style guide.

The details of the problem are as follows and exemplified in the minimal 
test case http://crosswire.org/~scribe/global_init_order_bug.tar.gz

D.cpp has file local globals with constructors (not, for example, const 
char *, which works fine)

main.cpp declares a global D instance object.

In this scenario, both compile units D.cpp and main.cpp have a global 
init which each need to run.  The C++ standard says that there is no 
order specified for which one runs first.

In the failure case main.cpp's global initialization runs first and 
tries to call methods on D (specifically D's c-tor) before D's global 
initialization has run.

Jaak has well pointed out the problem and the solution, which I have 
implemented in all of our option filters that used this pattern.  Thanks 
Jaak!

I just always unconsciously assumed the compile unit with main() would 
be initialized last, after all libraries had already been initialized-- 
and it seems that every version of every compiler we've ever tried 
before this recent version of g++ has implemented things this way.  But 
indeed the spec never says anything about the compile unit with main() 
being any different than any other compile unit, so there's nothing 
keeping a compiler from initializing it first.

Anyway, big commit, fairly uniform change, so not as big as it looks.  
All regression tests pass.  I'm not going to cut a new RC until I look 
at the recent post from John Austin tomorrow, so have a go at SVN if you 
have time.

Thanks again Jaak for the fix, and Peter for reporting the problem,

Troy



On 09/12/2013 12:07 PM, Jaak Ristioja wrote:
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> On 12.09.2013 09:54, Troy A. Griffitts wrote:
>> Thanks Jaak. I also tested surrounding the symbols in an anonymous
>> namespace but this alone did not fix the problem for me.
> Do I understand you correctly, that the patch worked, but just using
> an anonymous namespace didn't work? - This is what I think is to be
> expected. The anonymous namespace might just help prevent these
> globals from being exported as symbols from the library.
>
>> Can you explain again why there is even a problem at all?
>>
>> Again, every one of those globals is in the same compile unit and
>> in the correct order, top down. The initialization spec you cite
>> does not seem to explain the issue, unless I'm daft.
> No they are not in the same translation unit. The variable "oValues"
> is in utfgreekaccents.cpp:41 and "greekAccentsFilter" is in
> imp2gbs.cpp:62.
>
> Sorry, no time to explain. ;( But please read
>    http://www.parashift.com/c++-faq/ctors.html
> from 10.14(10.12) to 10.18, and the init_priority section from
>    http://gcc.gnu.org/onlinedocs/gcc/C_002b_002b-Attributes.html
>
> I hope this helps.
>
> Blessings,
> Jaak
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