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

[Pavel Labath via Phabricator via lldb-commits]

labath 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;
----------------
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:



Repository:
  rG LLVM Github Monorepo

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

https://reviews.llvm.org/D112931