[Lldb-commits] [PATCH] D112931: Fix mixed disassembly showing source lines for "line 0"

[Ted Woodward via Phabricator via lldb-commits]

ted added inline comments.


================
Comment at: lldb/test/Shell/Commands/command-disassemble-mixed.c:11-18
+int main(int argc, char **argv)
+{
+  int i;
+
+  for (i=0; i < 10; ++i) ;
+
+  return 0;
----------------
labath wrote:
> ted wrote:
> > labath wrote:
> > > ted wrote:
> > > > clayborg wrote:
> > > > > are we guaranteed to get some debug info with line zero in it with this example?
> > > > I tried this with x86 Linux clang 12.0 and our internal Hexagon clang; both gave me a line zero.
> > > > 
> > > > I ran this test on Ubuntu 18 using x86 Linux clang 12.0 and the test failed without the change and passed with it.
> > > Nonetheless, it would be better to test this via a .s file with some explicit .line directives. That way you could check for the actual command output instead of the absence of some string.
> > > 
> > > (Negative tests like this are very brittle, as they can be rendered ineffective by a change in the capitalization of the error message.)
> > The test is specifically "the first line of the source file is not displayed when we do dis -m". The only way I can think of testing this is a negative test.  If anyone can think of a better way, I'm happy to do that.
> > Fortunately, the message we're testing against is contained in the test, so it avoids the brittleness of changes to text in the tool.
> I missed the fact that this is a string coming from the test. That makes it better indeed, though I'd still recommend a .s file, as that also removes the dependence on the compiler producing a particular debug_line sequence.
> 
> Regarding the negative test, that's easy to avoid with a .s file, as you can assert exact command output. Something like this ought to do it (the test input should be alright, the assertions are made up).
> ```
> # RUN: llvm-mc -filetype=obj -triple x86_64-pc-linux %s -o %t
> # RUN: lldb %t -o "disassemble -m -n main" | FileCheck %s
> 
> # CHECK: disassemble -m -n main
> # CHECK-NEXT: first line of disassembly
> # CHECK-NEXT: second line of disassembly
> # CHECK-NEXT: etc.
> 
>         .text
>         .globl  main
>         .type   main, at function
> main:
>         .file   1 "" "mytest.s"
>         .loc    1 10
>         nop
>         .loc    1 0
>         nop
>         .loc    1 20
>         nop
> .Lfunc_end0:
>         .size   main, .Lfunc_end0-main
>                                         # -- End function
>         .section        .debug_abbrev,"", at progbits
>         .byte   1                               # Abbreviation Code
>         .byte   17                              # DW_TAG_compile_unit
>         .byte   0                               # DW_CHILDREN_no
>         .byte   37                              # DW_AT_producer
>         .byte   8                               # DW_FORM_string
>         .byte   19                              # DW_AT_language
>         .byte   5                               # DW_FORM_data2
>         .byte   3                               # DW_AT_name
>         .byte   8                               # DW_FORM_string
>         .byte   16                              # DW_AT_stmt_list
>         .byte   23                              # DW_FORM_sec_offset
>         .byte   17                              # DW_AT_low_pc
>         .byte   1                               # DW_FORM_addr
>         .byte   18                              # DW_AT_high_pc
>         .byte   6                               # DW_FORM_data4
>         .byte   0                               # EOM(1)
>         .byte   0                               # EOM(2)
>         .byte   0                               # EOM(3)
>         .section        .debug_info,"", at progbits
> .Lcu_begin0:
>         .long   .Ldebug_info_end0-.Ldebug_info_start0 # Length of Unit
> .Ldebug_info_start0:
>         .short  4                               # DWARF version number
>         .long   .debug_abbrev                   # Offset Into Abbrev. Section
>         .byte   8                               # Address Size (in bytes)
>         .byte   1                               # Abbrev [1] 0xb:0x1f DW_TAG_compile_unit
>         .asciz  "Hand-written DWARF"            # DW_AT_producer
>         .short  12                              # DW_AT_language
>         .asciz  "mytest.s"                      # DW_AT_name
>         .long   .Lline_table_start0             # DW_AT_stmt_list
>         .quad   main                            # DW_AT_low_pc
>         .long   .Lfunc_end0-main                # DW_AT_high_pc
> .Ldebug_info_end0:
>         .section        .debug_line,"", at progbits
> .Lline_table_start0:
> 
My issues with the above:

  - I want to test a c source file, not an assembly file.
  - This assumes the user's toolchain supports x86-64, which many downstream toolchains do not. I'd rather the test be core-agnostic, which is why I didn't check any actual disassembly.






Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D112931/new/

https://reviews.llvm.org/D112931