[PATCH] D62462: [llvm-objdump] Add warning messages if disassembly + source for problematic inputs
James Henderson via Phabricator via llvm-commits
llvm-commits at lists.llvm.org
Thu Jul 11 01:41:39 PDT 2019
jhenderson added inline comments.
================
Comment at: llvm/test/tools/llvm-objdump/X86/source-interleave-no-debug-info.test:12
+# WARN: warning: failed to parse debug info from file <invalid>
# CHECK: 0000000000000010 main:
----------------
mmpozulp wrote:
> jhenderson wrote:
> > mmpozulp wrote:
> > > jhenderson wrote:
> > > > Hmm... Not sure about this one. I think we need a different message in that case, since '<invalid>' isn't actually a file.
> > > I think `failed to parse debug info` is a bit better than `failed to parse debug info from file "<invalid>"`. Here's what the user sees
> > >
> > > ```
> > > [mike at gannon build]$ ./bin/llvm-objdump --source test/tools/llvm-objdump/X86/Output/source-interleave-no-debug-info.test.tmp2.o
> > >
> > > test/tools/llvm-objdump/X86/Output/source-interleave-no-debug-info.test.tmp2.o: file format ELF64-x86-64
> > >
> > >
> > > Disassembly of section .text:
> > >
> > > 0000000000000000 foo:
> > > ./bin/llvm-objdump: warning: failed to parse debug info
> > > 0: 55 pushq %rbp
> > > 1: 48 89 e5 movq %rsp, %rbp
> > > 4: 8b 05 00 00 00 00 movl (%rip), %eax
> > > a: 5d popq %rbp
> > > b: c3 retq
> > > c: 90 nop
> > > d: 90 nop
> > > e: 90 nop
> > > f: 90 nop
> > >
> > > 0000000000000010 main:
> > > 10: 55 pushq %rbp
> > > 11: 48 89 e5 movq %rsp, %rbp
> > > 14: 53 pushq %rbx
> > > 15: 48 83 ec 18 subq $24, %rsp
> > > 19: c7 45 f4 00 00 00 00 movl $0, -12(%rbp)
> > > 20: 48 c7 45 e8 00 00 00 00 movq $0, -24(%rbp)
> > > 28: 8b 1d 00 00 00 00 movl (%rip), %ebx
> > > 2e: e8 cd ff ff ff callq -51 <foo>
> > > 33: 01 d8 addl %ebx, %eax
> > > 35: 48 83 c4 18 addq $24, %rsp
> > > 39: 5b popq %rbx
> > > 3a: 5d popq %rbp
> > > 3b: c3 retq
> > >
> > > ```
> > They'll only see this if standard output and standard error are printed to the same stream. I think you need something indicating the file in most cases, where possible.
> >
> > Thinking about your previous version (reporting "invalid"), that sounds like something's wrong. Why isn't it able to print the object file name here? How could it be in an invalid state in that context? Sure, the debug info in the object file might be invalid, but that doesn't affect the file name of the object.
> > Why isn't it able to print the object file name here?
>
> In this test, we "failed to parse debug info" because it was stripped from the object file.
> ```
> [mike at gannon build]$ ./bin/llvm-dwarfdump test/tools/llvm-objdump/X86/Output/source-interleave-no-debug-info.test.tmp2.o
> test/tools/llvm-objdump/X86/Output/source-interleave-no-debug-info.test.tmp2.o: file format ELF64-x86-64
>
> .debug_info contents:
> ```
> Thus, `LineInfo.FileName == "<invalid>"` for every instruction. Here is the output from dwarfdump on the unstripped file (that is, before running `llvm-objcopy --strip-debug`). The filename `/home/mike/ws/llvm/llvm-project/llvm/test/tools/llvm-objdump/X86/Inputs/source-interleave-x86_64.c` is present.
>
> ```[mike at gannon build]$ ./bin/llvm-dwarfdump test/tools/llvm-objdump/X86/Output/source-interleave-no-debug-info.test.tmp.o
> test/tools/llvm-objdump/X86/Output/source-interleave-no-debug-info.test.tmp.o: file format ELF64-x86-64
>
> .debug_info contents:
> 0x00000000: Compile Unit: length = 0x00000089 version = 0x0004 abbr_offset = 0x0000 addr_size = 0x08 (next unit at 0x0000008d)
>
> 0x0000000b: DW_TAG_compile_unit
> DW_AT_producer ("clang version 4.0.0")
> DW_AT_language (DW_LANG_C99)
> DW_AT_name ("source-interleave-x86_64.c")
> DW_AT_stmt_list (0x00000000)
> DW_AT_comp_dir ("/home/mike/ws/llvm/llvm-project/llvm/test/tools/llvm-objdump/X86/Inputs")
> DW_AT_GNU_pubnames (true)
> DW_AT_low_pc (0x0000000000000000)
> DW_AT_high_pc (0x000000000000003c)
>
> 0x0000002a: DW_TAG_variable
> DW_AT_name ("a")
> DW_AT_type (0x0000003f "int")
> DW_AT_external (true)
> DW_AT_decl_file ("/home/mike/ws/llvm/llvm-project/llvm/test/tools/llvm-objdump/X86/Inputs/source-interleave-x86_64.c")
> DW_AT_decl_line (1)
> DW_AT_location (DW_OP_addr 0x0)
>
> 0x0000003f: DW_TAG_base_type
> DW_AT_name ("int")
> DW_AT_encoding (DW_ATE_signed)
> DW_AT_byte_size (0x04)
>
> 0x00000046: DW_TAG_subprogram
> DW_AT_low_pc (0x0000000000000000)
> DW_AT_high_pc (0x000000000000000c)
> DW_AT_frame_base (DW_OP_reg6 RBP)
> DW_AT_name ("foo")
> DW_AT_decl_file ("/home/mike/ws/llvm/llvm-project/llvm/test/tools/llvm-objdump/X86/Inputs/source-interleave-x86_64.c")
> DW_AT_decl_line (2)
> DW_AT_type (0x0000003f "int")
> DW_AT_external (true)
>
> 0x0000005f: DW_TAG_subprogram
> DW_AT_low_pc (0x0000000000000010)
> DW_AT_high_pc (0x000000000000003c)
> DW_AT_frame_base (DW_OP_reg6 RBP)
> DW_AT_name ("main")
> DW_AT_decl_file ("/home/mike/ws/llvm/llvm-project/llvm/test/tools/llvm-objdump/X86/Inputs/source-interleave-x86_64.c")
> DW_AT_decl_line (6)
> DW_AT_type (0x0000003f "int")
> DW_AT_external (true)
>
> 0x00000078: DW_TAG_variable
> DW_AT_location (DW_OP_fbreg -24)
> DW_AT_name ("b")
> DW_AT_decl_file ("/home/mike/ws/llvm/llvm-project/llvm/test/tools/llvm-objdump/X86/Inputs/source-interleave-x86_64.c")
> DW_AT_decl_line (7)
> DW_AT_type (0x00000087 "int*")
>
> 0x00000086: NULL
>
> 0x00000087: DW_TAG_pointer_type
> DW_AT_type (0x0000003f "int")
>
> 0x0000008c: NULL
>
> ```
> How do we recover the filename after stripping?
Isn't the name you want to report in this message the object file, not the source? That's the thing that's useful in this context (e.g. it could be "warning: unable to find debug information for object.o"). The problem here is in the object, not the source.
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