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cmd/compile: autotmp_ variables included in DWARF #17644

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aarzilli opened this issue Oct 28, 2016 · 4 comments
Closed

cmd/compile: autotmp_ variables included in DWARF #17644

aarzilli opened this issue Oct 28, 2016 · 4 comments
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FrozenDueToAge NeedsFix The path to resolution is known, but the work has not been done.
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Go1.8

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@aarzilli
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Please answer these questions before submitting your issue. Thanks!

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

go version devel +f595848 Fri Oct 28 04:36:31 2016 +0000 linux/amd64

What operating system and processor architecture are you using (go env)?

GOARCH="amd64"
GOBIN=""
GOEXE=""
GOHOSTARCH="amd64"
GOHOSTOS="linux"
GOOS="linux"
GOPATH="/home/a/n/go/"
GORACE=""
GOROOT="/usr/local/go-tip"
GOTOOLDIR="/usr/local/go-tip/pkg/tool/linux_amd64"
GCCGO="gccgo"
CC="gcc"
GOGCCFLAGS="-fPIC -m64 -pthread -fmessage-length=0 -fdebug-prefix-map=/tmp/go-build802960213=/tmp/go-build -gno-record-gcc-switches"
CXX="g++"
CGO_ENABLED="1"
PKG_CONFIG="pkg-config"
CGO_CFLAGS="-g -O2"
CGO_CPPFLAGS=""
CGO_CXXFLAGS="-g -O2"
CGO_FFLAGS="-g -O2"
CGO_LDFLAGS="-g -O2"

What did you do?

Complied this with gcflags='-N -l' then ran objdump --dwarf on the output.

What did you expect to see?

No autotmp_nn variables in .debug_info.

What did you see instead?

 <1><1901a>: Abbrev Number: 2 (DW_TAG_subprogram)
    <1901b>   DW_AT_name        : main.main
    <19025>   DW_AT_low_pc      : 0x44a4e0
    <1902d>   DW_AT_high_pc     : 0x44a550
    <19035>   DW_AT_external    : 1
 <2><19036>: Abbrev Number: 4 (DW_TAG_variable)
    <19037>   DW_AT_name        : i
    <19039>   DW_AT_location    : 4 byte block: 9c 11 50 22     (DW_OP_call_frame_cfa; DW_OP_consts: -48; DW_OP_plus)
    <1903e>   DW_AT_type        : <0x1b07e>
 <2><19046>: Abbrev Number: 4 (DW_TAG_variable)
    <19047>   DW_AT_name        : i#1
    <1904b>   DW_AT_location    : 4 byte block: 9c 11 58 22     (DW_OP_call_frame_cfa; DW_OP_consts: -40; DW_OP_plus)
    <19050>   DW_AT_type        : <0x1b07e>
 <2><19058>: Abbrev Number: 4 (DW_TAG_variable)
    <19059>   DW_AT_name        : autotmp_1
    <19063>   DW_AT_location    : 4 byte block: 9c 11 60 22     (DW_OP_call_frame_cfa; DW_OP_consts: -32; DW_OP_plus)
    <19068>   DW_AT_type        : <0x1b07e>
 <2><19070>: Abbrev Number: 4 (DW_TAG_variable)
    <19071>   DW_AT_name        : autotmp_0
    <1907b>   DW_AT_location    : 4 byte block: 9c 11 68 22     (DW_OP_call_frame_cfa; DW_OP_consts: -24; DW_OP_plus)
    <19080>   DW_AT_type        : <0x1b07e>
 <2><19088>: Abbrev Number: 0

This bug was introduced by commit d80e8de see also #17240
@gopherbot
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CL https://golang.org/cl/32159 mentions this issue.

@dr2chase dr2chase mentioned this issue Oct 28, 2016
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@gopherbot
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CL https://golang.org/cl/32255 mentions this issue.

@quentinmit quentinmit added the NeedsFix The path to resolution is known, but the work has not been done. label Oct 28, 2016
@quentinmit quentinmit added this to the Go1.8 milestone Oct 28, 2016
@gopherbot
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CL https://golang.org/cl/32419 mentions this issue.

@gopherbot
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CL https://golang.org/cl/33233 mentions this issue.

gopherbot pushed a commit that referenced this issue Nov 16, 2016
@dr2chase
cmd/compile: ensure necessary types appear in .debug_info
9f5673d 
Autotmp filtering was too aggressive and excluded types
necessary to make debuggers work properly.  Restore the
"late filter" in dwarf.go based on names to exclude autotmps,
and remove the "early filter" in pgen.go based on how the
name was introduced.  However, the updated naming scheme
with a dot prefix is retained to prevent accidental clashes
with legal Go identifier names.

Includes test (grouped with runtime gdb tests),
verified to fail without the fix.

Updates #17644.
Fixes #17830.

Change-Id: I7ec3f7230083889660236e5f6bc77ba5fe434e93
Reviewed-on: https://go-review.googlesource.com/33233
Run-TryBot: David Chase <[email protected]>
TryBot-Result: Gobot Gobot <[email protected]>
Reviewed-by: Matthew Dempsky <[email protected]>
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