Segfault instead of throwing UndefVarError — includes rr trace

[jmert]

The test case from this discourse question leads to a segfault after the local function definitions are changed to either anonymous functions (which I tried locally) or local assignment of different functions (as shown in the third reply).

A later reply identified just changing @error to error() in the function definition avoids the segfault. The else branch doesn't define showcase(), so the later call should result in an UndefVarError being thrown. (The earlier observation that error() works is because that cases the function to throw an actual error and exit the function before the call following the if-else block is called.)

I've tried out Julia v1.5's new julia --bug-report=rr tool — the rr dump was uploaded to https://s3.amazonaws.com/julialang-dumps/reports/2020-08-28T15-12-54-jmert.tar.zst

Julia version:

julia> versioninfo()
Julia Version 1.5.0-beta1.0
Commit 6443f6c95a (2020-05-28 17:42 UTC)
Platform Info:
  OS: Linux (x86_64-pc-linux-gnu)
  CPU: Intel(R) Core(TM) i7-7500U CPU @ 2.70GHz
  WORD_SIZE: 64
  LIBM: libopenlibm
  LLVM: libLLVM-9.0.1 (ORCJIT, skylake)

(I had to switch to my Intel laptop since rr doesn't run on Ryzen, and I didn't realize I still had the beta installed on the laptop. I can reproduce with v1.5.1 if need be.)

Test script:

using Printf

function switchcase(i, str)
    case = str
    if uppercase(case) == "A"
        @info "set case A"
        showcase = i -> @printf("case A number %i", i)
    elseif uppercase(case) == "B"
        @info "set case B"
        showcase = i -> @printf("case B number %i and some more parameters %i", i, 8)
    else
        @error("no case $case")
    end
    showcase(i)
end

switchcase(2, "C")

[lmiq]

Simpler test script:

f() = 1
g() = 2
function h(i)
  if i == 1
    s = f
  elseif i == 2
    s = g
  else
    @error("none")
  end
  s()
end
h(1)

[maleadt]

Slightly simpler, and without the macro:

a() = 0
b() = 0
function c(d)
  if 0
    e = a
  elseif 0
    e = b
  else
    try
    catch 
    end
  end
  e
end
c(0)

[yuyichao]

Making this line https://github.com/JuliaLang/julia/blob/master/src/codegen.cpp#L6840 conditional on VN should fix it without any other effect though I'm not 100% sure if this should happen.