Bug#700737: binutils-gold: produces different symbols for webkit

[Matthias Klose]

[CC-ing dpkg]

Am 17.02.2013 11:27, schrieb Jonathan Nieder:
> tags 700737 + moreinfo
> quit
> 
> Hi Michael,
> 
> Michael Gilbert wrote:
> 
>> - (optional|c++)"WebCore::TextIterator::getLocationAndLengthFromRange(WebCore::Element*, WebCore::Range const*, unsigned int&, unsigned int&)@Base" 1.7.4
>> +#MISSING: 1.8.1-3.3# (optional|c++)"WebCore::TextIterator::getLocationAndLengthFromRange(WebCore::Element*, WebCore::Range const*, unsigned int&, unsigned int&)@Base" 1.7.4
> 
> From the dpkg-gensymbols(1) manpage:
> 
> 	optional
> 		A symbol marked as optional can disappear from the
> 		library at any time and that will never cause
> 		dpkg-gensymbols to fail.
> 
> [...]
>> @@ -213,6 +213,7 @@
>>   _NPN_SetException at Base 1.3.10
>>   _NPN_SetProperty at Base 1.3.10
>>   _NPN_UTF8FromIdentifier at Base 1.3.10
>> + _ZdlPv at Base 1.8.1-3.3
> 
> c++filt tells me this is operator delete(void*).
> 
> So presumably an entry
> 
> 	(optional|c++)"operator delete(void*)"
> 
> would suppress the build failure.  Can you say a little more about
> whether this is a gold bug?  Do binaries built against versions of
> libwebkit built with gold rely on this symbol and fail when run
> against libwebkit built with ld.bfd?
> 
> In C++, different lists of exported symbols based on the phase of moon
> are completely normal, for example when template instantiation is
> involved.  So more details would be welcome.

I think that dpkg-gensymbols is misleading in that it treats all symbols
exported as the same, not differentiating where they come from. Yes, you do have
the option to mark a symbol as optional, however marking a symbol as coming from
another library (libstdc++, Webkit:Core) would help too, but would require some
work by the package maintainer too. Whether a template operator or another
template from another library ends up as an exported symbol depends on the
toolchain (different compiler/linker, different version, different optimization
level), and that should not be encoded in the symbols files.

  Matthias