Re: [PATCH] gdb/dwarf2: Add support for DW_LNS_set_epilogue_begin in line-table

[Guinevere Larsen <blarsen@redhat.com>]

On 10/01/2024 17:57, Simon Marchi wrote:
> On 12/21/23 05:29, Guinevere Larsen wrote:
>> This commit adds a mechanism for GDB to detect the linetable opcode
>> DW_LNS_set_epilogue_begin. This opcode is set by compilers to indicate
>> that a certain instruction marks the point where the frame is destroyed.
>>
>> While the standard allows for multiple points marked with epilogue_begin
>> in the same function, for performance reasons, the function that
>> searches for the epilogue address will only find the last address that
>> sets this flag for a given block.
>>
>> This commit also changes amd64_stack_frame_destroyed_p_1 to attempt to
>> use the epilogue begin directly, and only if an epilogue can't be found
>> will it attempt heuristics based on the current instruction.
>>
>> Finally, this commit also changes the dwarf assembler to be able to emit
>> epilogue-begin instructions, to make it easier to test this patch
> Starting with this commit, I see:
>
> FAIL: gdb.base/unwind-on-each-insn-amd64.exp: foo: instruction 6: $fba_value == $fn_fba
> FAIL: gdb.base/unwind-on-each-insn-amd64.exp: foo: instruction 6: check frame-id matches
> FAIL: gdb.base/unwind-on-each-insn-amd64.exp: foo: instruction 6: bt 2
> FAIL: gdb.base/unwind-on-each-insn-amd64.exp: foo: instruction 6: up
> FAIL: gdb.base/unwind-on-each-insn-amd64.exp: foo: instruction 6: $sp_value == $::main_sp
> FAIL: gdb.base/unwind-on-each-insn-amd64.exp: foo: instruction 6: $fba_value == $::main_fba
> FAIL: gdb.base/unwind-on-each-insn-amd64.exp: foo: instruction 6: [string equal $fid $::main_fid]
>
> Do you see it?
>
Hi Simon,

I don't see anything wrong with this test locally, I get 179 expected 
passes. Could it be some difference in config?

-- 
Cheers,
Guinevere Larsen
She/Her/Hers