[lldb-dev] LLDB can't find source...but it can?

[Greg Clayton via lldb-dev]

> On Oct 7, 2016, at 4:53 PM, Ted Woodward via lldb-dev <lldb-dev at lists.llvm.org> wrote:
> 
> Background – I’m working on getting LLDB to run on Hexagon Linux, built with an LLVM toolchain. We’re using libc++ and MUSL. The loader is a bit squirrelly right now, so I’ve built LLDB statically.
>  
> I’ve got full source debugging in the driver, but when I step into SBDebugger::Create, I don’t have any source. I’ve got symbols:
> (lldb) bt
> * thread #1: tid = 1, 0x00114730 lldb`lldb::SBDebugger::Create(bool) + 16, stop reason = breakpoint 2.1
>   * frame #0: 0x00114730 lldb`lldb::SBDebugger::Create(bool) + 16
>     frame #1: 0x000001dc lldb`Driver::Driver(this=0x7ffefc50) + 124 at Driver.cpp:150
>     frame #2: 0x00006aa0 lldb`main(argc=1, argv=0x7ffefd34) + 240 at Driver.cpp:1350
>     frame #3: 0x04744384 lldb`__libc_start_main + 48
>  
> list SBDebugger::Create fails, but list SBDebugger::Create(bool) gives me source.
> (lldb) list SBDebugger::Create
> (lldb) list SBDebugger::Create(bool)
> File: \local\mnt\workspace\ted\linux\llvm\tools\lldb\source\API\SBDebugger.cpp
>    172      return SBDebugger::Create(false, nullptr, nullptr);
>    173  }
>    174
>    175  SBDebugger
>    176  SBDebugger::Create(bool source_init_files)
>    177  {
>    178      return SBDebugger::Create (source_init_files, nullptr, nullptr);
>    179  }
>    180
>    181  SBDebugger
>    182  SBDebugger::Create(bool source_init_files, lldb::LogOutputCallback callback, void *baton)
>    183
>  
> Finally, I try to list based on the address of the function:
> (lldb) list 0x114720
> error: address resolves to lldb[0x0000000000114720], but there is no line table information available for this address.
>  
> But there is line table information for 0x114720 (from llvm-dwarfdump):
> 0x0000000000114720    177      0     80   0             0  is_stmt
> 0x0000000000114730    178     32     80   0             0  is_stmt prologue_end
> 0x0000000000114734    178     12     80   0             0 
> 0x0000000000114754    178      5     80   0             0
>  
>  
>  
> My breakpoint at SBDebugger::Create resolved to prologue_end:
> (lldb) break list
> Current breakpoints:
> 1: name = 'main', locations = 1, resolved = 1, hit count = 1
>   1.1: where = lldb`main + 32 at Driver.cpp:1335, address = 0x000069d0, resolved, hit count = 1
>  
> 2: name = 'SBDebugger::Create', locations = 3, resolved = 3, hit count = 1
>   2.1: where = lldb`lldb::SBDebugger::Create(bool) + 16, address = 0x00114730, resolved, hit count = 1
>   2.2: where = lldb`lldb::SBDebugger::Create() + 8, address = 0x001143c0, resolved, hit count = 0
>   2.3: where = lldb`lldb::SBDebugger::Create(bool, void (*)(char const*, void*), void*) + 40, address = 0x00114404, resolved, hit count = 0
>  
>  
> So – why can LLDB find the source when I specify the function explicitly, or find the line table info when I set a breakpoint, but not when I am in the function or list an address?
>  

Probably a debug info problem. Before we know to look for addresses within a compile unit, the compile unit must claim it has a function that contains this address. So check the DWARF in the compile unit that contains 0x114720 (not sure if there is a lookup by address in llmv-dwarfdump?) and make sure there is a DW_TAG_subprogram that contains this address. 

Greg

> Ted
>  
> --
> Qualcomm Innovation Center, Inc.
> The Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum, a Linux Foundation Collaborative Project
>  
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