[LLVMdev] LTOModule::parseSymbols not handling GlobalAlias

Shankar Easwaran
Thu, 02 Oct 2014 16:35:11 -0000

Hi,

There is a genuine case that lto_module_get_num_symbols doesnot return
all the symbols that are in the bitcode file.

Test case:-

cat > test.c << \!
int bar() { return 0; }
int foo()  __attribute__ ((weak, alias ("bar")));
!

clang -c test.c -emit-llvm

Use a program to list all the symbols using lto_module_get_num_symbols, and foo
will be missing from the list.

Thanks

Shankar Easwaran

On 10/2/2014 11:22 AM, Sergei Larin wrote:
> Hello everyone,
>
>    ...I should have used a different subject line in the first place...
>
>
> I've asked Rafael a question about GlobalAlias handling in
> LTOModule::parseSymbols, but he seems to be on vacation...
>
>
> Does anyone knows the answer?
>
> Thanks a lot!
>
> Sergei
>
>
> ---
> Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum, hosted
by
> The Linux Foundation
>
>
>> -----Original Message-----
>> From: llvmdev-bounces at cs.uiuc.edu [mailto:llvmdev-bounces at
cs.uiuc.edu]
>> On Behalf Of Sergei Larin
>> Sent: Thursday, October 02, 2014 11:06 AM
>> To: 'Rafael Espíndola'
>> Cc: 'LLVM Developers Mailing List'
>> Subject: Re: [LLVMdev] [RFC] Exhaustive bitcode compatibility tests for
IR
>> features
>>
>>
>> Hi Rafael,
>>
>>    I have a quick question for you. First of all I am not very familiar
> with this
>> code, so....
>>
>>
>> Before this change:
>>
>> [llvm] r212349 - Implement LTOModule on top of IRObjectFile
>> http://comments.gmane.org/gmane.comp.compilers.llvm.cvs/195450
>>
>>
>> LTOModule::parseSymbols used to explicitly add global aliases as
defined
>> symbols:
>>
>>    // add aliases
>>   for (const auto &Alias : IRFile->aliases())
>>      addDefinedDataSymbol(Alias);
>>
>> After your patch I do not seem to see an explicit handling of
aliases... I
> would
>> naively expect something like this:
>>
>> for (auto &Sym : IRFile->symbols()) {
>> .....
>>      if (isa<GlobalVariable>(GV)) {
>>        addDefinedDataSymbol(Sym);
>>        continue;
>>      }
>>
>>      if (isa<GlobalAlias>(GV)) {
>>        addDefinedDataSymbol(Sym);
>>        continue;
>>      }
>>
>> }
>>
>>
>>   Is this an oversight or a design decision? If this is the later,
> when/where
>> aliases should be handled?
>> Thanks a lot.
>>
>> Sergei
>>
>>
>>
>>
>> ---
>> Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum,
>> hosted by The Linux Foundation
>>
>>
>>
>> _______________________________________________
>> LLVM Developers mailing list
>> LLVMdev at cs.uiuc.edu         http://llvm.cs.uiuc.edu
>> http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev
>
> _______________________________________________
> LLVM Developers mailing list
> LLVMdev at cs.uiuc.edu         http://llvm.cs.uiuc.edu
> http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev


--
Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum, hosted by the
Linux Foundation