[LLVMdev] Problem with InsertPointGuard ABI?

[Reid Kleckner]

The layout of AssertingVH has depended on NDEBUG since 2009, which predates
any of our efforts to make LLVM's ABI resilient to mismatched NDEBUG
definitions between LLVM and its users.

For now, make sure your definition of NDEBUG matches LLVM's. In the long
run, we could conceivably do something with LLVM_ENABLE_ABI_BREAKING_CHECKS
to allow this mismatch.

On Mon, Jul 13, 2015 at 6:39 AM, Paweł Bylica <chfast at gmail.com> wrote:

> Hi,
>
> I have problem with IRBuilderBase::InsertPointGuard class that simply does
> not work in the release build of my project. The class does not restore the
> IRBuilder's insert point correctly when NDEBUG macro is set. It happens on
> OSX system only, trunk version of the LLVM built with brew.
>
> I suspect it is the ABI problem. InsertPointGuard uses AssertingVT for
> debug builds.
>
> LLDB gets confused also. The first listing shows that the instance of
> InsertPointGuard is messed up:
>
>    96   auto check = _builder.GetInsertBlock();
>    97   {
>    98   llvm::IRBuilderBase::InsertPointGuard guard{_builder};
> -> 99   _builder.SetInsertPoint(checkBB);
>    100 }
>    101
>    102 if (_builder.GetInsertBlock() != check)
> (lldb) p _builder
> (llvm::IRBuilder<true, llvm::ConstantFolder,
> llvm::IRBuilderDefaultInserter<true> >) $4 = {
>   llvm::IRBuilderBase = {
>     CurDbgLocation = {
>       Loc = {
>         Ref = {
>           MD = 0x0000000000000000
>         }
>       }
>     }
>     BB = 0x000000010642ecf0
>     InsertPt = {
>       NodePtr = 0x000000010642ed00
>     }
>     Context = 0x000000010642d170
>     DefaultFPMathTag = 0x0000000000000000
>     FMF = (Flags = 0)
>   }
>   Folder = {}
> }
> (lldb) p guard
> (llvm::IRBuilderBase::InsertPointGuard) $5 = {
>   Builder = 0x00007fff5fbf46d8
>   Block = {
>     ThePtr = 0x0000000107800398
>   }
>   Point = {
>     NodePtr = 0x0000000000000000
>   }
>   DbgLoc = {
>     Loc = {
>       Ref = {
>         MD = 0x000000010642ecf0
>       }
>     }
>   }
> }
>
> Moreover, if I start printing the guard from InsertPointGuard constructor
> it shows different data layout. LLDB also crashes after step out and
> printing the guard again.
>
>    195   public:
>    196     InsertPointGuard(IRBuilderBase &B)
>    197         : Builder(B), Block(B.GetInsertBlock()),
> Point(B.GetInsertPoint()),
> -> 198           DbgLoc(B.getCurrentDebugLocation()) {}
>    199
>    200     ~InsertPointGuard() {
>    201       Builder.restoreIP(InsertPoint(Block, Point));
> (lldb) p *this
> (llvm::IRBuilderBase::InsertPointGuard) $6 = {
>   Builder = 0x00007fff5fbf4440
>   Block = {
>     llvm::ValueHandleBase = {
>       PrevPair = (Value = 4337803886)
>       Next = 0x000000010615b0a8
>       V = 0x000000010615b170
>     }
>   }
>   Point = {
>     NodePtr = 0x000000010615b140
>   }
>   DbgLoc = {
>     Loc = {
>       Ref = {
>         MD = 0x000000010324444b
>       }
>     }
>   }
> }
> (lldb) n
> Process 1498 stopped
> * thread #1: tid = 0x493aa8, 0x0000000102920b22
> libevmjit.0.0.dylib`dev::eth::jit::test(_builder=0x00007fff5fbf46d8) + 258
> at RuntimeManager.cpp:99, queue = 'com.apple.main-thread', stop reason =
> step over
>     frame #0: 0x0000000102920b22
> libevmjit.0.0.dylib`dev::eth::jit::test(_builder=0x00007fff5fbf46d8) + 258
> at RuntimeManager.cpp:99
>    96   auto check = _builder.GetInsertBlock();
>    97   {
>    98   llvm::IRBuilderBase::InsertPointGuard guard{_builder};
> -> 99   _builder.SetInsertPoint(checkBB);
>    100 }
>    101
>    102 if (_builder.GetInsertBlock() != check)
> (lldb) p guard
> Assertion failed: (field_idx < record_layout.getFieldCount()), function
> GetChildClangTypeAtIndex, file
> /SourceCache/lldb/lldb-320.4.156/source/Symbol/ClangASTType.cpp, line 6615.
> Abort trap: 6
>
> It's hard to create a small executable where the problem can be reproduced.
>
> Cheers,
> - Paweł Bylica
>
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>
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