llvm dev - Jan 2020 - Crash in SmallVector with latest MSVC 2019 (debug mode)

Is anybody using the LLVM/clang/lldb compiled with the MSVC 2019
(x86-32bit) successfully?
I am getting crash in SmallVector at multiple places after a
llvm:SmallVector is being moved around in move constructor or move
operator=.
 Not sure what is going on.

  ~SmallVectorImpl() {
    if (!this->isSmall())
      free(this->begin());  // <=== crash here, line 336 SmallVector.h
  }

The crash occurs only with clang compile in debug mode. Release mode is
fine.
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> The crash occurs only with clang compile in debug mode.
Sanity check: you're not mixing clang in debug mode with LLVM in release
mode, right?
I've seen similar crashes in DenseMap when I *accidentally* did the above.
________________________________
From: llvm-dev <llvm-dev-bounces at lists.llvm.org> on behalf of Francois
Pichet via llvm-dev <llvm-dev at lists.llvm.org>
Sent: Wednesday, January 22, 2020 1:00 PM
To: llvm-dev at lists.llvm.org <llvm-dev at lists.llvm.org>
Subject: [llvm-dev] Crash in SmallVector with latest MSVC 2019 (debug mode)

Is anybody using the LLVM/clang/lldb compiled with the MSVC 2019 (x86-32bit)
successfully?
I am getting crash in SmallVector at multiple places after a llvm:SmallVector is
being moved around in move constructor or move operator=.
 Not sure what is going on.

  ~SmallVectorImpl() {
    if (!this->isSmall())
      free(this->begin());  // <=== crash here, line 336 SmallVector.h
  }

The crash occurs only with clang compile in debug mode. Release mode is fine.

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I don't think there is anymore upstream LLVM testing for 32-bit MSVC.
I'll
run a local build in this configuration and look into it. I'll use this
compiler version:
Microsoft (R) C/C++ Optimizing Compiler Version 19.24.28315 for x86

We had so many issues in clang-cl around calling conventions for
"small"
objects with interior pointers, I wouldn't be surprised if there are bugs.

On Wed, Jan 22, 2020 at 10:01 AM Francois Pichet via llvm-dev <
llvm-dev at lists.llvm.org> wrote:
> Is anybody using the LLVM/clang/lldb compiled with the MSVC 2019
> (x86-32bit) successfully?
> I am getting crash in SmallVector at multiple places after a
> llvm:SmallVector is being moved around in move constructor or move
> operator=.
>  Not sure what is going on.
>
>   ~SmallVectorImpl() {
>     if (!this->isSmall())
>       free(this->begin());  // <=== crash here, line 336
SmallVector.h
>   }
>
> The crash occurs only with clang compile in debug mode. Release mode is
> fine.
>
> _______________________________________________
> LLVM Developers mailing list
> llvm-dev at lists.llvm.org
> https://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev
>
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I was able to reproduce the problem. It seems to relate to the use of a
UniqueVector (which uses std::vector internally) of SmallVectors here:
https://github.com/llvm/llvm-project/blob/master/llvm/utils/TableGen/DFAEmitter.h#L91

Aside from potential MSVC bugs, this is a poor choice of data structures. I
would suggest using a SmallVector<T, 0> or std::vector<T> instead.
So, we
could commit that as a workaround.

Relatedly, debug MSVC tablegen builds are still unusably slow. :(
https://bugs.llvm.org/show_bug.cgi?id=28222

On Wed, Jan 22, 2020 at 11:15 AM Reid Kleckner <rnk at google.com> wrote:
> I don't think there is anymore upstream LLVM testing for 32-bit MSVC.
I'll
> run a local build in this configuration and look into it. I'll use this
> compiler version:
> Microsoft (R) C/C++ Optimizing Compiler Version 19.24.28315 for x86
>
> We had so many issues in clang-cl around calling conventions for
"small"
> objects with interior pointers, I wouldn't be surprised if there are
bugs.
>
> On Wed, Jan 22, 2020 at 10:01 AM Francois Pichet via llvm-dev <
> llvm-dev at lists.llvm.org> wrote:
>
>> Is anybody using the LLVM/clang/lldb compiled with the MSVC 2019
>> (x86-32bit) successfully?
>> I am getting crash in SmallVector at multiple places after a
>> llvm:SmallVector is being moved around in move constructor or move
>> operator=.
>>  Not sure what is going on.
>>
>>   ~SmallVectorImpl() {
>>     if (!this->isSmall())
>>       free(this->begin());  // <=== crash here, line 336
SmallVector.h
>>   }
>>
>> The crash occurs only with clang compile in debug mode. Release mode is
>> fine.
>>
>> _______________________________________________
>> LLVM Developers mailing list
>> llvm-dev at lists.llvm.org
>> https://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev
>>
>
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