Can't show variable value by p in gdb (DW_FORM_strp)

[coolg92003]

when I build envoy by "-c dbg", then run by gdb and try to check variable value and get below info

**p socket_->isOpen())**
DW_FORM_strp pointing outside of .debug_str section [in module /build/.cache/bazel/_bazel_envoybuild/b570b5ccd0454dc9af9f65ab1833764d/execroot/envoy/bazel-out/k8-dbg/bin/source/exe/envoy-static]
**p read_end_stream_**
DW_FORM_strp pointing outside of .debug_str section [in module /build/.cache/bazel/_bazel_envoybuild/b570b5ccd0454dc9af9f65ab1833764d/execroot/envoy/bazel-out/k8-dbg/bin/source/exe/envoy-static]

anything or path missed? and check below for details:

1. build
   cd /source; export PATH bazel build -c dbg //source/exe:envoy
2. run
   gdb /build/.cache/bazel/_bazel_envoybuild/b570b5ccd0454dc9af9f65ab1833764d/execroot/envoy/ba
   zel-out/k8-dbg/bin/source/exe/envoy-static
   b ConnectionImpl::onRead
   run -l trace --concurrency 1 -c /tmp/sesDySecLCnoDEnvoy.yaml --log-path /tmp/envoy.log
3. trigger message
4. check variable
   p this->read_end_stream_
   DW_FORM_strp pointing outside of .debug_str section [in module /build/.cache/bazel/_bazel_envoybuild/b570b5ccd0454dc9af9f65ab1833764d/execroot/envoy/bazel-out/k8-dbg/bin/source/exe/envoy-static]

thanks
Cliff

[ravenblackx]

@KBaichoo has been looking at debug symbol related things recently and may have some insight.

[coolg92003]

Hi @KBaichoo ,
Would you share some idea on this?
Thanks in advance!
Cliff

[coolg92003]

The major concern is that it can't show the content of *this

[KBaichoo]

See my PR here: #33942 for a brief overview on some debug symbols related stuff.

I'd check that the section being referenced exists.
Also what version of clang / gcc are you using? Likewise with gdb ?

I've ran into some issues of using newer toolchains with older gdb versions.

[coolg92003]

hi @KBaichoo ,
Really Appreciated your reply! in our build container(ubuntu), I didn't find clang and see below for gdb and gcc version:
gdb --version
GNU gdb (Ubuntu 10.2-0ubuntu120.041) 10.2
Copyright (C) 2021 Free Software Foundation, Inc.
License GPLv3+: GNU GPL version 3 or later http://gnu.org/licenses/gpl.html
gcc --version
gcc (Ubuntu 11.4.0-2ubuntu1~20.04) 11.4.0
Copyright (C) 2021 Free Software Foundation, Inc.

BTW, which version of gdb and gcc works for you?
I mean that it can read *this in gdb for envoy built by "-c dbg"
thanks,
Cliff

[KBaichoo]

neither of those versions look too old.

I actually build with clang 14 (which is what CI is using) and use gdb GNU gdb (GDB) 14.2. I know some other folks have tried use lldb when debugging and run into issues using gdb.

FWIW I'm able to get the value printed as expected following your experiment:

Thread 8 "wrk:worker_0" hit Breakpoint 1, Envoy::Network::ConnectionImpl::onRead (this=0x26a0bd3f6000, read_buffer_size=79)
    at source/common/network/connection_impl.cc:357
357       ASSERT(dispatcher_.isThreadSafe());
(gdb) p this->read_end_stream_
$1 = false

And these are the segments I have from in the debug build:

[11:16:27] kbaichoo:envoy:0 $size --format=SysV bazel-bin/source/exe/envoy-static    
bazel-bin/source/exe/envoy-static  :
section                     size        addr
.interp                       28         736
.note.ABI-tag                 32         764
.note.gnu.build-id            36         796
.dynsym                    14088         832
.gnu.version                1174       14920
.gnu.version_r               560       16096
.gnu.hash                   1396       16656
.dynstr                     7286       18052
.rela.dyn                7981248       25344
.rela.plt                   9600     8006592
.rodata                  9880792     8019968
.gcc_except_table        2210936    17900760
protodesc_cold            581552    20111696
flags_help_cold             5452    20693248
.eh_frame_hdr            8443644    20698700
.eh_frame               34644932    29142344
.text                   97679155    63791424
.init                         27   161470580
.fini                         13   161470608
google_malloc             815665   161470656
malloc_hook                  553   162286322
.plt                        6416   162286880
.tdata                       192   162297408
.tbss                       9581   162297600
.fini_array                    8   162297600
.init_array                17320   162297608
.data.rel.ro             2895800   162314928
.dynamic                     512   165210728
.got                         296   165211240
.got.plt                    3224   165211536
.data                     381560   165218880
.tm_clone_table                0   165600440
__rseq_cs                   2624   165600448
__rseq_cs_ptr_array          656   165603072
.bss                    10189248   165603776
.comment                      97           0
.debug_abbrev             245791           0
.debug_info              2565679           0
.debug_str_offsets        580120           0
.debug_str                668320           0
.debug_addr             60972824           0
.debug_line            363996157           0
.debug_line_str           497779           0
.debug_rnglists         27153314           0
.debug_loclists           445938           0
.debug_aranges              1056           0
.debug_frame                  96           0
.gdb_index             382380659           0
Total                 1015293436

In bazel-bin I have the following:

[11:18:37] kbaichoo:bazel-bin:0 $find . -name *.dwp
[11:18:41] kbaichoo:bazel-bin:0 $find . -name *.dwo
./external/com_github_alibaba_hessian2_codec/hessian2/_objs/codec_impl_lib/codec.pic.dwo
./external/com_github_alibaba_hessian2_codec/hessian2/_objs/reader_lib/reader.pic.dwo
./external/com_github_alibaba_hessian2_codec/hessian2/basic_codec/_objs/byte_codec_lib/byte_codec.pic.dwo
...

No dwp files but many dwo.

[coolg92003]

Congratulations!
I still can't print *this
thanks
Cliff

[coolg92003]

hi @KBaichoo ,
After building by below command, then gdb can show everything

cd /source; export PATH CC=clang CXX=clang++ && bazel build --define tcmalloc=debug -c dbg --copt=-Wno-unknown-warning-option --copt=-Wno-unused-but-set-variable --cxxopt=-Wno-unknown-warning-option --cxxopt=-Wno-unused-but-set-variable //source/exe:envoy

hope it help!
Cliff