[m-dev.] Bug 321

Paul Bone paul at bone.id.au
Sat Feb 22 13:15:50 AEDT 2014

On Fri, Feb 21, 2014 at 11:24:02PM +1100, Julien Fischer wrote:
> On Fri, 21 Feb 2014, Paul Bone wrote:
>> I'm tracking down bug 321.  https://www.mercurylang.org/bugs/view.php?id=321
>> As you recall this is the symptom:
>>    The C linker gives me errors such as:
>>    paul at oxygen> mmc --rebuild test -O2 --intermodule-optimization
>>    Making Mercury/int3s/test.int3
>>    Making Mercury/ints/test.int
>>    Making Mercury/opts/test.opt
>>    Making Mercury/cs/test.c
>>    Making Mercury/os/test.o
>>    Making test
>>    ** Error making `test'.
>>    Mercury/os/test.o: In function `<predicate 'test.try_divide'/3 mode
>>    0>':
>>    test.c:(.text+0xe6): undefined reference to `<predicate
>>    'exception.wrap_success_or_failure'/2 mode 0>'
>>    collect2: error: ld returned 1 exit status
>> After looking at the exception.m code and the HLDS dumps during compilation
>> of my test.m I found that:
>>    The linker can't find an address for: wrap_success_or_failure/2
>>    But it can find addresses for: get_determinism/2
> Is your test.m the same as the file bug321.m that you uploaded to
> Mantis?  I ask, because when I try the file from Mantis everything
> seems fine ...

Yes it is except for the module name.

>> Both predicates are called by the same code in the HLDS representation of
>> test.m but one works and what doesn't.
> ... and when I look at the HLDS dumps (of bug321.m)I see no reference to
> wrap_success_or_failure/2.

Are you using the same options as above and in the bug report -O2

>> So I looked at readelf(1) dump of libmer_std.so's symbol table.
>> get_determinism/2 is exported globally and wrap_success_or_failure/2 is
>> exported locally.
>> Both are declared and defined in the implementation section of the exception
>> module.  So now I want to know why is one being treated differently.
> get_determinism/2 is exported globally from exception.o because it
> is referred to by opt-exported clauses in optimization interface for the
> exception module.  (It is also subject of a no_inline pragma so its own
> clauses do not appear in the .opt file.)
> wrap_success_or_failure/2 is not exported because it only refererred by
> the predicate try_det, whose own clauses are not opt-exported.

Okay that's odd.  I'll look more closely.

Paul Bone

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