[Power] First execution of backtrace() includes itself in trace

[vchuravy]

julia> bt1 = backtrace()
37-element Vector{Union{Ptr{Nothing}, Base.InterpreterIP}}:
 Ptr{Nothing} @0x00007fff9eb4f0cf
 Ptr{Nothing} @0x00007fff9eb4f257
 Ptr{Nothing} @0x00007fffb24aa4f7
 Ptr{Nothing} @0x00007fffb24ca8eb
 Ptr{Nothing} @0x00007fffb24ca403
 Ptr{Nothing} @0x00007fffb24caf5b
 Ptr{Nothing} @0x00007fffb24cbe5f
 Base.InterpreterIP in top-level CodeInfo for Main at statement 0
...
julia> bt2=backtrace()
36-element Vector{Union{Ptr{Nothing}, Base.InterpreterIP}}:
 Ptr{Nothing} @0x00007fff9eb4f257
 Ptr{Nothing} @0x00007fffb24aa4f7
 Ptr{Nothing} @0x00007fffb24ca8eb
 Ptr{Nothing} @0x00007fffb24ca403
 Ptr{Nothing} @0x00007fffb24caf5b
 Ptr{Nothing} @0x00007fffb24cbe5f
 Base.InterpreterIP in top-level CodeInfo for Main at statement 0
...

julia> Base.show_backtrace(stderr, bt1)

Stacktrace:
  [1] backtrace()
    @ Base ./error.jl:112
  [2] top-level scope

julia> Base.show_backtrace(stderr, bt2)

Stacktrace:
  [1] top-level scope
    @ REPL[2]:1

breaks one of the errorshow tests

[vchuravy]

Also responsible for a test-failure in logging:

Error in testset Logging:
Test Failed at /nobackup/users/vchuravy/builds/julia-nodbg/usr/share/julia/stdlib/v1.7/Logging/test/runtests.jl:198
  Expression: startswith(genmsg("msg", exception = (DivideError(), bt)), "┌ PREFIX msg\n│   exception =\n│    DivideError: integer division error\n│    Stacktrace:\n│      [1] func1()")
   Evaluated: startswith("┌ PREFIX msg\n│   exception =\n│    DivideError: integer division error\n│    Stacktrace:\n│      [1] backtrace()\n│        @ Base ./error.jl:112\n│      [2] func1()\n│        @ Main.Test12Main_Logging /nobackup/
users/vchuravy/builds/julia-nodbg/usr/share/julia/stdlib/v1.7/Logging/test/runtests.jl:7\n│      [3] macro expansion\n│        @ /nobackup/users/vchuravy/builds/julia-nodbg/usr/share/julia/stdlib/v1.7/Logging/test/runtests.jl:197 [inlined
]\n│      [4] macro expansion\n│        @ /nobackup/users/vchuravy/builds/julia-nodbg/usr/share/julia/stdlib/v1.7/Test/src/Test.jl:1147 [inlined]\n│      [5] macro expansion\n│        @ /nobackup/users/vchuravy/builds/julia-nodbg/usr/shar
e/julia/stdlib/v1.7/Logging/test/runtests.jl:20 [inlined]\n│      [6] macro expansion\n│        @ /nobackup/users/vchuravy/builds/julia-nodbg/usr/share/julia/stdlib/v1.7/Test/src/Test.jl:1147 [inlined]\n│      [7] top-level scope\n│      
  @ /nobackup/users/vchuravy/builds/julia-nodbg/usr/share/julia/stdlib/v1.7/Logging/test/runtests.jl:11\n│      [8] include\n│        @ ./Base.jl:386 [inlined]\n│      [9] macro expansion\n│        @ /nobackup/users/vchuravy/dev/julia/tes
t/testdefs.jl:24 [inlined]\n│     [10] macro expansion\n│        @ /nobackup/users/vchuravy/builds/julia-nodbg/usr/share/julia/stdlib/v1.7/Test/src/Test.jl:1147 [inlined]\n│     [11] macro expansion\n│        @ /nobackup/users/vchuravy/de
v/julia/test/testdefs.jl:23 [inlined]\n│     [12] macro expansion\n│        @ ./timing.jl:353 [inlined]\n│     [13] runtests(name::String, path::String, isolate::Bool; seed::UInt128)\n│        @ Main /nobackup/users/vchuravy/dev/julia/tes
t/testdefs.jl:21\n│     [14] #137\n│        @ /nobackup/users/vchuravy/builds/julia-nodbg/usr/share/julia/stdlib/v1.7/Distributed/src/remotecall.jl:354 [inlined]\n│     [15] run_work_thunk(thunk::Distributed.var\"#137#138\"{typeof(runtest
s), Tuple{String, String}, Base.Iterators.Pairs{Symbol, UInt128, Tuple{Symbol}, NamedTuple{(:seed,), Tuple{UInt128}}}}, print_error::Bool)\n│        @ Distributed /nobackup/users/vchuravy/builds/julia-nodbg/usr/share/julia/stdlib/v1.7/Dis
tributed/src/process_messages.jl:63\n│     [16] remotecall_fetch(::Function, ::Distributed.LocalProcess, ::String, ::Vararg{String, N} where N; kwargs::Base.Iterators.Pairs{Symbol, UInt128, Tuple{Symbol}, NamedTuple{(:seed,), Tuple{UInt12
8}}})\n│        @ Distributed /nobackup/users/vchuravy/builds/julia-nodbg/usr/share/julia/stdlib/v1.7/Distributed/src/remotecall.jl:379\n│     [17] remotecall_fetch(::Function, ::Int64, ::String, ::Vararg{String, N} where N; kwargs::Base.
Iterators.Pairs{Symbol, UInt128, Tuple{Symbol}, NamedTuple{(:seed,), Tuple{UInt128}}})\n│        @ Distributed /nobackup/users/vchuravy/builds/julia-nodbg/usr/share/julia/stdlib/v1.7/Distributed/src/remotecall.jl:421\n│     [18] macro exp
ansion\n│        @ /nobackup/users/vchuravy/dev/julia/test/runtests.jl:217 [inlined]\n│     [19] (::var\"#29#39\"{Vector{Task}, var\"#print_testworker_errored#35\"{ReentrantLock, Int64, Int64}, var\"#print_testworker_stats#33\"{ReentrantL
ock, Int64, Int64, Int64, Int64, Int64, Int64}, Vector{Any}, Dict{String, DateTime}})()\n│        @ Main ./task.jl:406\n└ SUFFIX\n", "┌ PREFIX msg\n│   exception =\n│    DivideError: integer division error\n│    Stacktrace:\n│      [1] fu
nc1()")

[vchuravy]

Ah:

#0  jl_backtrace_from_here (returnsp=0, skip=1) at /nobackup/users/vchuravy/dev/julia/src/stackwalk.c:228
#1  0x00007fffe276eef0 in jlplt_jl_backtrace_from_here_12751 () from /nobackup/users/vchuravy/builds/julia/usr/lib/julia/sys-debug.so
#2  0x00007fffe216a8e4 in julia_backtrace_25029 () at error.jl:112
#3  0x00007fffe216ab40 in jfptr_backtrace_25030 () from /nobackup/users/vchuravy/builds/julia/usr/lib/julia/sys-debug.so

vis-a-vis:

(gdb) bt
#0  jl_backtrace_from_here (returnsp=0, skip=1) at /nobackup/users/vchuravy/dev/julia/src/stackwalk.c:228
#1  0x00007fffe216a8e4 in julia_backtrace_25029 () at error.jl:112
#2  0x00007fffe216ab40 in jfptr_backtrace_25030 () from /nobackup/users/vchuravy/builds/julia/usr/lib/julia/sys-debug.so
#3  0x00007ffff74b3d54 in _jl_invoke (F=0x7fffe3228c90 <jl_system_image_data+10058576>, args=0x7fffffff8998, nargs=0, mfunc=0x7fffe3228810 <jl_system_image_data+10057424>, world=29541) at /nobackup/users/vchuravy/dev/julia/src/gf.c:2205
#4  0x00007ffff74b4820 in jl_apply_generic (F=0x7fffe3228c90 <jl_system_image_data+10058576>, args=0x7fffffff8998, nargs=0) at /nobackup/users/vchuravy/dev/julia/src/gf.c:2406

So the first time we call backtrace, we go through the PLT and include that in the trace.