[llvm-dev] Miscompilation while switching from clang-4 to clang-5

Alex Denisov via llvm-dev llvm-dev at lists.llvm.org
Fri Jun 1 00:06:15 PDT 2018

Hi Tim,

The verbose mode is a good idea, thank you.

I've gathered all compilation commands with -v flag for clang-4 and clang-5 and they are identical (excerpt of compiler version).
I will try to find what has changed in clang/llvm between the versions.

If there are any other hints: send them my way :)

> On 31. May 2018, at 09:54, Tim Northover <t.p.northover at gmail.com> wrote:
> On 31 May 2018 at 08:41, Alex Denisov via llvm-dev
> <llvm-dev at lists.llvm.org> wrote:
>> I understand the linking problem. What I do not understand is how to debug the difference between two versions of compilers.
>> This what I do (briefly):
>> clang++-4 foobar.cpp -lLLVM -l/opt/llvm-3.9/lib
>> clang++-5 foobar.cpp -lLLVM -l/opt/llvm-3.9/lib
> If you add -v then Clang will output each individual command it runs
> to do that compilation (I'd expect 2: one compile step and one link
> step).
> As Tom & Michael said, the link step is most likely to be wrong. You
> could test that by mixing and matching the invocations (using the .o
> file produced by one version of Clang in the other link command for
> example). In the end though, I suspect you'll find it's linking
> against a different set of libraries now.
> Cheers.
> Tim.

Software Engineer, https://lowlevelbits.org
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