Fixes JuliaLang#18141, eliminating null in value when iterating over …

…`ENV`. (JuliaLang#18144)

* Eliminate trailing null from iterator over `ENV`.

Fixes JuliaLang#18141.

* Add failing test for JuliaLang#18141.

base/env.jl

@@ -91,15 +91,15 @@ if is_windows()
  function next(hash::EnvHash, block::Tuple{Ptr{UInt16},Ptr{UInt16}})
  pos = block[1]
  blk = block[2]
- len = ccall(:wcslen, UInt, (Ptr{UInt16},), pos) + 1
+ len = ccall(:wcslen, UInt, (Ptr{UInt16},), pos)
  buf = Array{UInt16}(len)
  unsafe_copy!(pointer(buf), pos, len)
  env = transcode(String, buf)
  m = match(r"^(=?[^=]+)=(.*)$"s, env)
  if m === nothing
  error("malformed environment entry: $env")
  end
- return (Pair{String,String}(m.captures[1], m.captures[2]), (pos+len*2, blk))
+ return (Pair{String,String}(m.captures[1], m.captures[2]), (pos+(len+1)*2, blk))
  end
 else # !windows
  start(::EnvHash) = 0

test/env.jl

@@ -63,3 +63,10 @@ end
 
 # Test for #10853
 @test withenv(Dict{Any,Any}()...) do; true; end
+
+# Test for #18141
+for (k, v) in ENV
+ if length(v) > 0
+ @test v[end] != '\0'
+ end
+end