PkgId objects change by printing and returning from function

[lgoettgens]

Running the following prints the UUID of Aqua as expected (on 1.10.3, 1.11.0-beta1, and b54dce2 (few days old master)):

using Pkg
Pkg.activate(; temp=true)
Pkg.add(["Aqua"])
Pkg.instantiate()

function foo()
    pkgid = Base.identify_package("Aqua")
    return pkgid
end

println(foo().uuid)

However, if we move the printing into the function, makes the code behave differently in different julia versions:

using Pkg
Pkg.activate(; temp=true)
Pkg.add(["Aqua"])
Pkg.instantiate()

function foo()
    pkgid = Base.identify_package("Aqua")
    println(pkgid.uuid)
end

foo()

output 1.10.3:

4c88cf16-eb10-579e-8560-4a9242c79595

output 1.11.0-beta1:

ERROR: LoadError: type Nothing has no field uuid
Stacktrace:
 [1] getproperty
   @ ./Base.jl:49 [inlined]
 [2] foo()
   @ Main ~/code/julia/julia/foo.jl:9
 [3] top-level scope
   @ ~/code/julia/julia/foo.jl:13

output b54dce2 (few days old master):

ERROR: LoadError: type Nothing has no field uuid
Stacktrace:
 [1] getproperty
   @ ./Base.jl:49 [inlined]
 [2] foo()
   @ Main ~/code/julia/julia/foo.jl:9
 [3] top-level scope
   @ ~/code/julia/julia/foo.jl:13
 [4] include
   @ ./Base.jl:559 [inlined]
 [5] exec_options(opts::Base.JLOptions)
   @ Base ./client.jl:325
 [6] _start()
   @ Base ./client.jl:533

If we add another print in there, the LoadError transforms into a segfault:

using Pkg
Pkg.activate(; temp=true)
Pkg.add(["Aqua"])
Pkg.instantiate()

function foo()
    pkgid = Base.identify_package("Aqua")
    println(pkgid)
    println(pkgid.uuid)
end

foo()

output 1.10.3:

Aqua [4c88cf16-eb10-579e-8560-4a9242c79595]
4c88cf16-eb10-579e-8560-4a9242c79595

output 1.11.0-beta1:

Base.PkgId(Base.UUID("4c88cf16-eb10-579e-8560-4a9242c79595"), "Aqua")

[925569] signal 11 (128): Segmentation fault
in expression starting at /home/lgoe/code/julia/julia/foo.jl:13
foo at /home/lgoe/code/julia/julia/foo.jl:6
unknown function (ip: 0x7417e9b3158f)
unknown function (ip: (nil))
Allocations: 6884270 (Pool: 6882848; Big: 1422); GC: 8
[1]    925569 segmentation fault (core dumped)  julia +1.11 foo.jl

output b54dce2 (few days old master):

Base.PkgId(Base.UUID("4c88cf16-eb10-579e-8560-4a9242c79595"), "Aqua")

[925819] signal 11 (128): Segmentation fault
in expression starting at /home/lgoe/code/julia/julia/foo.jl:13
foo at /home/lgoe/code/julia/julia/foo.jl:6
unknown function (ip: 0x7d7afbb2adff)
unknown function (ip: (nil))
Allocations: 4446232 (Pool: 4444892; Big: 1340); GC: 6
[1]    925819 segmentation fault (core dumped)  julia +nightly foo.jl

some device information:

Platform Info:
  OS: Linux (x86_64-linux-gnu)
  CPU: 8 × Intel(R) Core(TM) i7-10510U CPU @ 1.80GHz
  WORD_SIZE: 64
  LIBM: libopenlibm
  LLVM: libLLVM-15.0.7 (ORCJIT, skylake)

all three julia versions are installed via juliaup

cc @fingolfin

[fingolfin]

I see that @gbaraldi has a fix for this, great! In case it helps further: git bisect pinpoints the start of this to 00cbe4a from PR #53326 by @vtjnash but of course that change may have only exposed an instance of an already existing condition.

[fingolfin]

Looking at the proposed fix it seems Julia is generating invalid code here, ouch