[lldb-dev] LLDB can't find source...but it can?
Greg Clayton via lldb-dev
lldb-dev at lists.llvm.org
Mon Oct 17 09:02:58 PDT 2016
This is a compiler bug.
> On Oct 14, 2016, at 12:14 PM, Ted Woodward <ted.woodward at codeaurora.org> wrote:
>
>> 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
>
> I'm changing gears here - I'm having the same issue with lldb-server, and it's smaller, so I'm looking at that.
>
> main calls main_gdbserver, which is in tools/lldb-server/lldb-gdbserver.cpp, and has no line table info, according to lldb's list comm info.
>
> 4: name = 'main_gdbserver', locations = 2
> 4.1: where = lldb-server`main_gdbserver(int, char**) + 32, address = 0x00048964, unresolved, hit count = 0
> 4.2: where = lldb-server`main_gdbserver(int, char**) + 32, address = 0x00048964, unresolved, hit count = 0
>
> (lldb) list 0x48964
> error: address resolves to lldb-server[0x0000000000048964], but there is no line table information available for this address.
>
>
> main_gdbserver has a DW_AT_subprogram entry:
> 0x000306a4: DW_TAG_subprogram [106] *
> DW_AT_low_pc [DW_FORM_addr] (0x0000000000048944)
> DW_AT_high_pc [DW_FORM_data4] (0x00000da4)
> DW_AT_frame_base [DW_FORM_exprloc] (<0x1> 6e )
> DW_AT_linkage_name [DW_FORM_strp] ( .debug_str[0x0006577b] = "_Z14main_gdbserveriPPc")
> DW_AT_name [DW_FORM_strp] ( .debug_str[0x00065792] = "main_gdbserver")
> DW_AT_decl_file [DW_FORM_data1] ("/local/mnt/workspace/ted/linux/llvm/tools/lldb/tools/lldb-server/lldb-gdbserver.cpp")
> DW_AT_decl_line [DW_FORM_data2] (326)
> DW_AT_type [DW_FORM_ref4] (cu + 0x003b => {0x00011c13})
> DW_AT_external [DW_FORM_flag_present] (true)
>
> And a linetable entry:
> 0x0000000000048944 327 0 1 0 0 is_stmt
> 0x0000000000048964 328 11 1 0 0 is_stmt prologue_end
>
>
>
> --
> Qualcomm Innovation Center, Inc.
> The Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum, a Linux Foundation Collaborative Project
>
>> -----Original Message-----
>> From: Greg Clayton [mailto:gclayton at apple.com]
>> Sent: Tuesday, October 11, 2016 1:34 PM
>> To: Ted Woodward <ted.woodward at codeaurora.org>
>> Cc: LLDB <lldb-dev at lists.llvm.org>
>> Subject: Re: [lldb-dev] LLDB can't find source...but it can?
>>
>>
>>> 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.cp
>> p
>>> 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?
>>>
>>
>>
>>> Ted
>>>
>>> --
>>> Qualcomm Innovation Center, Inc.
>>> The Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum,
>> a Linux Foundation Collaborative Project
>>>
>>> _______________________________________________
>>> lldb-dev mailing list
>>> lldb-dev at lists.llvm.org
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>
>
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