[lldb-dev] LLDB can't find source...but it can?
Greg Clayton via lldb-dev
lldb-dev at lists.llvm.org
Mon Oct 17 10:26:53 PDT 2016
Send me the file offline. I will help narrow it down for you.
> On Oct 17, 2016, at 9:58 AM, Ted Woodward <ted.woodward at codeaurora.org> wrote:
>
> What's the compiler bug? I see a DW_AT_subprogram entry for main_gdbserver, and linetable entries for the addresses of main_gdbserver.
>
> I've found that getting DWARF compiler bugs fixed can be...challenging. The better I can narrow it down for the compiler engineers, the better.
>
> This is clang that was ToT about 2 months ago, BTW.
>
> --
> 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: Monday, October 17, 2016 11:03 AM
>> 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?
>>
>> 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
>>>>> http://lists.llvm.org/cgi-bin/mailman/listinfo/lldb-dev
>>>
>>>
>
>
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