[lldb-dev] Need help on LLDB on Fedora x86_64 Linux

[Todd Fiala]

Hi Xu,Chiheng,

Locally I'm using this patch to work around the issue.  I'm not yet sure if
it's the right fix since I haven't had cycles to dig into the root cause
yet, but it does get me past the seg faults in the scenarios I'm using.
 This patch is against the llvm repo:

https://llvm.org/svn/llvm-project/llvm/trunk@203176

--- a/lib/MC/MCExternalSymbolizer.cpp
+++ b/lib/MC/MCExternalSymbolizer.cpp
@@ -132,7 +132,8 @@ bool
MCExternalSymbolizer::tryAddingSymbolicOperand(MCInst &MI,
       Expr = MCConstantExpr::Create(0, Ctx);
   }

-  Expr = RelInfo->createExprForCAPIVariantKind(Expr,
SymbolicOp.VariantKind);
+  if (RelInfo)
+      Expr = RelInfo->createExprForCAPIVariantKind(Expr,
SymbolicOp.VariantKind);
   if (!Expr)
     return false;


On Thu, Mar 6, 2014 at 6:05 AM, Xu,Chiheng <chiheng.xu at gmail.com> wrote:

> Hi, list,
> When I use lastest LLDB(and Clang/LLVM) to debug a hello world program
> on Fedora 18 x86_64 Linux. I encounter a crash of LLDB.  I have
> debugged LLDB using gdb-7.6.2, and found that the offending line is :
>
> Breakpoint 3, llvm::MCExternalSymbolizer::tryAddingSymbolicOperand (
>     this=0x7fe470000c50, MI=..., cStream=..., Value=258220247920,
>     Address=258220234131, IsBranch=true, Offset=1, InstSize=4)
>     at /mnt/work/llvm/lib/MC/MCExternalSymbolizer.cpp:135
> 135       Expr = RelInfo->createExprForCAPIVariantKind(Expr,
> SymbolicOp.VariantKind);
>
> where RelInfo (of type std::unique_ptr<MCRelocationInfo>) is 0, so
> LLDB crash, I'm new to this, can some one explain this to me.
>
> LLDB does not has this problem about 2 weeks ago.
> Attached is the debug log.
>
> Thank you.
>
> --
> Xu,Chiheng(徐持恒)
>
> _______________________________________________
> lldb-dev mailing list
> lldb-dev at cs.uiuc.edu
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>
>


-- 
Todd Fiala | Software Engineer | tfiala at google.com | 650-943-3180
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