[lldb-dev] LLDB can't find source...but it can?
Ted Woodward via lldb-dev
lldb-dev at lists.llvm.org
Mon Oct 17 09:58:11 PDT 2016
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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