From 9d0d599dbedb90810285e7a082a2c64b2fb00573 Mon Sep 17 00:00:00 2001
From: Valentin Churavy <v.churavy@gmail.com>
Date: Mon, 14 Dec 2020 16:12:14 -0500
Subject: [PATCH] Unset TMPDIR for tempname

---
 base/file.jl | 12 ++++++++----
 test/file.jl |  8 ++++++++
 2 files changed, 16 insertions(+), 4 deletions(-)

diff --git a/base/file.jl b/base/file.jl
index d76e81f62364e8..37cbbc01a6ba0a 100644
--- a/base/file.jl
+++ b/base/file.jl
@@ -578,10 +578,14 @@ else # !windows
 # Obtain a temporary filename.
 function tempname(parent::AbstractString=tempdir(); cleanup::Bool=true)
     isdir(parent) || throw(ArgumentError("$(repr(parent)) is not a directory"))
-    p = ccall(:tempnam, Cstring, (Cstring, Cstring), parent, temp_prefix)
-    systemerror(:tempnam, p == C_NULL)
-    s = unsafe_string(p)
-    Libc.free(p)
+    # If TEMPDIR is set tempname will ignore `parent` as an argument (#38873)
+    s = withenv("TMPDIR" => nothing) do
+        p = ccall(:tempnam, Cstring, (Cstring, Cstring), parent, temp_prefix)
+        systemerror(:tempnam, p == C_NULL)
+        s = unsafe_string(p)
+        Libc.free(p)
+        return s
+    end
     cleanup && temp_cleanup_later(s)
     return s
 end
diff --git a/test/file.jl b/test/file.jl
index 2a2de0d7932159..50859742445b7b 100644
--- a/test/file.jl
+++ b/test/file.jl
@@ -71,6 +71,14 @@ end
         t = tempname(d)
         @test dirname(t) == d
     end
+    # 38873: check that `TMPDIR` being set does not
+    # override the parent argument to `tempname`.
+    mktempdir() do d
+        whithenv("TMPDIR"=>tmpdir()) do
+            t = tempname(d)
+            @test dirname(t) == d
+        end
+    end
     @test_throws ArgumentError tempname(randstring())
 end