It’s not too difficult to implement, something like that in file.scm:
#>
# define C_mkstemps(buf, extlen) C_fix(mkstemps(C_c_string(buf),
C_unfix(extlen)))
# define C_close(fd) C_fix(close(C_unfix(fd)))
<#
(set! create-temporary-file
(lambda (#!optional (ext "tmp"))
(##sys#check-string ext 'create-temporary-file)
(let* ((n (number-of-bytes ext))
;; Account for the added dot.
(n (if (fx= n 0) 0 (fx+ n 1)))
(pn (make-pathname
(tempdir)
(string-append temp-prefix "XXXXXX")
ext))
(r (##core#inline "C_mkstemps" (##sys#make-c-string pn
'create-temporary-file) n)))
(if (fx= r -1)
(##sys#signal-hook
#:file-error 'create-temporary-file
(##sys#string-append "cannot create temporary file - " strerror)
pn)
(begin
(##core#inline "C_close" r)
pn)))))
And then of course dig through the respective Windows APIs to make it work
there:
https://learn.microsoft.com/en-us/cpp/c-runtime-library/reference/mktemp-s-wmktemp-s?view=msvc-170
(Or just keep the current loop on Windows - _wpktemp_s is slightly quirky).
One could also hypothesise that call-with-temporary-file has the right to exist
as well,
giving access to the port and the underlying fd.
Let’s see what Felix thinks. If he says that either is worth doing, I will be
happy
to make the patch.
--
Stan
> On 17 Sep 2026, at 20:20, Diego A. Mundo via Chicken-users
> <[email protected]> wrote:
>
>
> On Thursday, September 17th, 2026 at 13:56, Daniel Colascione via
> Chicken-users <[email protected]> wrote:
>
>> Why not just use mkstemp on platforms that support it and outsource the
>> fiddly bits?
>
> I think the why not may merely be that nobody has prioritized it and actually
> done the patch yet. I was just looking at what this would entail. We do have
> a file-mkstemp in (chicken file posix), which is implemented with mkstemp on
> unix and a custom function on windows, but:
>
> a) At least the Unix version is currently broken on master, something to do
> with the new string representation and u8 vectors, though this seems like a
> simple fix.
> b) This would be a backward-incompatible change, right? Which might be fine,
> I just don't see that mkstemp has a way to create a temp file with a
> particular extension. I don't know how many people were using that feature of
> create-temporary-file.
>
> Diego
>
