cmd/compile: escaped local variables aren't assigned to the correct lexical block in debug_info

[aarzilli]

Please answer these questions before submitting your issue. Thanks!

What version of Go are you using (go version)?

1.9 beta 2

What did you do?

Compiled this program with -gcflags '-N -l', ran objdump --dwarf

Result:

 <1><26358>: Abbrev Number: 2 (DW_TAG_subprogram)
    <26359>   DW_AT_name        : main.main
    <26363>   DW_AT_low_pc      : 0x487a50
    <2636b>   DW_AT_high_pc     : 0x487ce7
    <26373>   DW_AT_frame_base  : 1 byte block: 9c      (DW_OP_call_frame_cfa)
    <26375>   DW_AT_external    : 1
 <2><26376>: Abbrev Number: 4 (DW_TAG_variable)
    <26377>   DW_AT_name        : &a
    <2637a>   DW_AT_location    : 5 byte block: 9c 11 e8 7e 22  (DW_OP_call_frame_cfa; DW_OP_consts: -152; DW_OP_plus)
    <26380>   DW_AT_type        : <0x32175>
 <2><26384>: Abbrev Number: 6 (DW_TAG_lexical_block)
    <26385>   DW_AT_ranges      : 0x0
 <3><26389>: Abbrev Number: 4 (DW_TAG_variable)
    <2638a>   DW_AT_name        : a
    <2638c>   DW_AT_location    : 5 byte block: 9c 11 b0 7e 22  (DW_OP_call_frame_cfa; DW_OP_consts: -208; DW_OP_plus)
    <26392>   DW_AT_type        : <0x27f27>
 <3><26396>: Abbrev Number: 6 (DW_TAG_lexical_block)
    <26397>   DW_AT_ranges      : 0x40
 <4><2639b>: Abbrev Number: 4 (DW_TAG_variable)
    <2639c>   DW_AT_name        : p
    <2639e>   DW_AT_location    : 5 byte block: 9c 11 c8 7e 22  (DW_OP_call_frame_cfa; DW_OP_consts: -184; DW_OP_plus)
    <263a4>   DW_AT_type        : <0x32175>
 <4><263a8>: Abbrev Number: 0
 <3><263a9>: Abbrev Number: 0
 <2><263aa>: Abbrev Number: 0

The &a variable should have been inside the second lexical block, together with p.

[gopherbot]

CL https://golang.org/cl/47852 mentions this issue.

[aarzilli]

cc @mdempsky

[odeke-em]

I've updated the milestone to Go1.9 as per the consensus on the CL.