tempname ignores parent argument when environment variable TMPDIR is set

[vchuravy]

compiler/validation                (31) |        started at 2020-12-14T10:40:17.674           
compiler/validation                (31) |     2.18 |   0.09 |  4.2 |      56.87 |   303.75
file                               (31) |        started at 2020-12-14T10:40:20.769                                                                                                                                  
file                               (31) |         failed at 2020-12-14T10:40:42.395
Test Failed at /nobackup/users/vchuravy/dev/julia/test/file.jl:72
  Expression: dirname(t) == d
   Evaluated: "/tmp" == "/tmp/jl_b8KtOh"

I tried isolating it, but I have not yet reproduced it outside the tests themselves. Running file tests on it's own succeeds as well, but running make testall this is always reproducible.

[vchuravy]

The unaccounted for variable was running the tests under slurm vs on their own.

[vchuravy]

julia> ENV["TMPDIR"]
"/tmp"

julia> unsafe_string(ccall(:tempnam, Cstring, (Cstring, Cstring), "/nobackup", "jl_"))
"/tmp/jlUwwz4t"

and in the docs for tempnam

/* Generate a unique temporary filename using up to five characters of PFX
   if it is not NULL.  The directory to put this file in is searched for
   as follows: First the environment variable "TMPDIR" is checked.
   If it contains the name of a writable directory, that directory is used.
   If not and if DIR is not NULL, that value is checked.  If that fails,
   P_tmpdir is tried and finally "/tmp".  The storage for the filename
   is allocated by `malloc'.  */

[StefanKarpinski]

Seems like when parent is passed, we should ignore TMPDIR.

[KristofferC]

Dup of #35785.