[PATCH] D44388: [ELF] Rework debug line parsing to use llvm::Error (LLD-side)

[David Blaikie via llvm-commits]

(I will say "LTOrErr" is a slightly confusing variable name, given the
prevalence of "LTO" as a known acronym... )

On Mon, Mar 12, 2018 at 8:27 AM James Henderson via Phabricator via
llvm-commits <llvm-commits at lists.llvm.org> wrote:

> jhenderson created this revision.
> jhenderson added reviewers: ruiu, espindola.
> Herald added subscribers: arichardson, emaste.
>
> This is a companion change to https://reviews.llvm.org/D44382. That
> change changes the debug line parser interface to report LLVM errors, and
> to improve the error/warning reporting mechanism to not use fprintf(stderr,
> ...).
>
> As noted in the description on https://reviews.llvm.org/D44382, these
> warnings were not using the errs() stream, and so were not always being
> flushed properly by LLD on shutdown. To test this, I have extended the
> bad-debug undefined symbol message case to show that a corresponding
> warning is printed, if the debug line cannot be parsed.
>
>
> Repository:
>   rLLD LLVM Linker
>
> https://reviews.llvm.org/D44388
>
> Files:
>   ELF/InputFiles.cpp
>   test/ELF/Inputs/undef-bad-debug.s
>   test/ELF/undef.s
>
>
> Index: test/ELF/undef.s
> ===================================================================
> --- test/ELF/undef.s
> +++ test/ELF/undef.s
> @@ -34,6 +34,7 @@
>  # CHECK: >>> referenced by undef-debug.s:11 (dir{{/|\\}}undef-debug.s:11)
>  # CHECK: >>>               {{.*}}.o:(.text.2+0x0)
>
> +# CHECK: warning: parsing line table prologue at 0x00000000 should have
> ended at 0x00000038 but it ended at 0x00000037
>  # CHECK: error: undefined symbol: zed6
>  # CHECK: >>> referenced by {{.*}}tmp4.o:(.text+0x0)
>
> Index: test/ELF/Inputs/undef-bad-debug.s
> ===================================================================
> --- test/ELF/Inputs/undef-bad-debug.s
> +++ test/ELF/Inputs/undef-bad-debug.s
> @@ -1,7 +1,37 @@
>  .section .text,"ax"
>  sym:
>      .quad zed6
> -
> +
> +.section .debug_line,"", at progbits
> +    .long .Lunit_end - .Lunit_start # unit length
> +.Lunit_start:
> +    .short 4                        # version
> +    .long .Lprologue_end - .Lprologue_start # prologue length
> +.Lprologue_start:
> +    .byte 1                         # minimum instruction length
> +    .byte 1                         # maximum operatiosn per instruction
> +    .byte 1                         # default is_stmt
> +    .byte -5                        # line base
> +    .byte 14                        # line range
> +    .byte 13                        # opcode base
> +    .byte 0, 1, 1, 1, 1, 0, 0, 0, 1, 0, 0, 1 # standard opcode lengths
> +    .asciz "dir"                    # include directories
> +    .byte 0
> +    .asciz "undef-bad-debug.s"      # file names
> +    .byte 1, 0, 0
> +    .byte 0
> +    .byte 0                         # extraneous byte
> +.Lprologue_end:
> +    .byte 0, 9, 2                   # DW_LNE_set_address
> +    .quad sym
> +    .byte 3                         # DW_LNS_advance_line
> +    .byte 10
> +    .byte 1                         # DW_LNS_copy
> +    .byte 2                         # DW_LNS_advance_pc
> +    .byte 8
> +    .byte 0, 1, 1                   # DW_LNE_end_sequence
> +.Lunit_end:
> +
>  .section .debug_info,"", at progbits
>      .long   .Lcu_end - .Lcu_start   # Length of Unit
>  .Lcu_start:
> Index: ELF/InputFiles.cpp
> ===================================================================
> --- ELF/InputFiles.cpp
> +++ ELF/InputFiles.cpp
> @@ -124,8 +124,11 @@
>    // The second parameter is offset in .debug_line section
>    // for compilation unit (CU) of interest. We have only one
>    // CU (object file), so offset is always 0.
> -  const DWARFDebugLine::LineTable *LT =
> -      DwarfLine->getOrParseLineTable(LineData, 0, Dwarf, nullptr);
> +  auto LTOrErr = DwarfLine->getOrParseLineTable(LineData, 0, Dwarf,
> nullptr);
> +  const DWARFDebugLine::LineTable *LT = LTOrErr.Table;
> +  handleAllErrors(std::move(LTOrErr.Err),
> +                  [&](DebugLineError &Err) { warn(Err.message()); },
> +                  [&](ErrorInfoBase &Err) { error(Err.message()); });
>    if (!LT)
>      return;
>
>
>
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