[lld] r282633 - Warn on empty archive files.

[Nico Weber via llvm-commits]

libtool (on mac) warns on this, and it's spectacularly unhelpful. We filter
out that warning in a wrapper script since there's no flag to turn it off
and the warning is just noise in our build. If lld gets this warning,
please provide a way to toggle it off.

On Sep 30, 2016 12:31 PM, "Reid Kleckner" <rnk at google.com> wrote:

> Are you sure we should be warning on empty archives? This comes up in
> Chromium's build, which apparently has an archive with no symbols:
> https://build.chromium.org/p/chromium.fyi/builders/
> ClangToTLinuxLLD/builds/1596/steps/compile/logs/stdio
>
> That build also doesn't involve LTO, so the long explanatory comment isn't
> helpful.
>
> On Wed, Sep 28, 2016 at 2:10 PM, Rui Ueyama via llvm-commits <
> llvm-commits at lists.llvm.org> wrote:
>
>> Author: ruiu
>> Date: Wed Sep 28 16:10:54 2016
>> New Revision: 282633
>>
>> URL: http://llvm.org/viewvc/llvm-project?rev=282633&view=rev
>> Log:
>> Warn on empty archive files.
>>
>> Differential Revision: https://reviews.llvm.org/D25044
>>
>> Modified:
>>     lld/trunk/ELF/InputFiles.cpp
>>     lld/trunk/test/ELF/empty-archive.s
>>
>> Modified: lld/trunk/ELF/InputFiles.cpp
>> URL: http://llvm.org/viewvc/llvm-project/lld/trunk/ELF/InputFiles
>> .cpp?rev=282633&r1=282632&r2=282633&view=diff
>> ============================================================
>> ==================
>> --- lld/trunk/ELF/InputFiles.cpp (original)
>> +++ lld/trunk/ELF/InputFiles.cpp Wed Sep 28 16:10:54 2016
>> @@ -427,8 +427,17 @@ template <class ELFT> void ArchiveFile::
>>    File = check(Archive::create(MB), "failed to parse archive");
>>
>>    // Read the symbol table to construct Lazy objects.
>> -  for (const Archive::Symbol &Sym : File->symbols())
>> +  bool IsEmpty = true;
>> +  for (const Archive::Symbol &Sym : File->symbols()) {
>>      Symtab<ELFT>::X->addLazyArchive(this, Sym);
>> +    IsEmpty = false;
>> +  }
>> +
>> +  if (IsEmpty)
>> +    warning(getName() + " has no symbol. Chances are you are doing "
>> +            "an LTO build and forgot to use an ar command that can
>> create "
>> +            "a symbol table for LLVM bitcode files. If so, use llvm-ar
>> or "
>> +            "GNU ar + plugin.");
>>  }
>>
>>  // Returns a buffer pointing to a member file containing a given symbol.
>>
>> Modified: lld/trunk/test/ELF/empty-archive.s
>> URL: http://llvm.org/viewvc/llvm-project/lld/trunk/test/ELF/empty
>> -archive.s?rev=282633&r1=282632&r2=282633&view=diff
>> ============================================================
>> ==================
>> --- lld/trunk/test/ELF/empty-archive.s (original)
>> +++ lld/trunk/test/ELF/empty-archive.s Wed Sep 28 16:10:54 2016
>> @@ -1,3 +1,5 @@
>>  // RUN: llvm-ar rc %t.a
>>  // RUN: llvm-mc -filetype=obj -triple=x86_64-pc-linux %s -o %t.o
>> -// RUN: ld.lld -shared %t.o %t.a -o t
>> +// RUN: ld.lld -shared %t.o %t.a -o t 2>&1 | FileCheck %s
>> +
>> +// CHECK: has no symbol.
>>
>>
>> _______________________________________________
>> llvm-commits mailing list
>> llvm-commits at lists.llvm.org
>> http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-commits
>>
>
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.llvm.org/pipermail/llvm-commits/attachments/20160930/a59e85d7/attachment.html>