Re: [PATCH] Windows: Normalize backward slashes to forward slashes

[Pedro Alves <pedro@palves.net>]

On 2026-06-30 12:26, Eli Zaretskii wrote:
>> From: Pedro Alves <pedro@palves.net>
>> Date: Mon, 29 Jun 2026 22:24:30 +0100
>>
>>   Starting program: C:/msys2/home/alves/gdb/build-testsuite/outputs/gdb.rocm/simple/simple
> 
> Are forward slashes only shown to the user, or does the code pas the
> file name with forward slashes to CreateProcess?  (I'm not familiar
> with thecode enough to determine which one myself, sorry.)  If we pass
> forward slashes to CreateProcess, it could cause problems, IME; it is
> much safer to use backslashes there.

We now pass forward slashes down to CreateProcess.  It just works on my Windows 11 machine, though.  I forgot to
mention, but I (painfully) ran the whole testsuite before and after this patch (that's how I discovered the need
to tweak the gdb.base/set-cwd.exp testcase).

Searching online, I found this:

  https://stackoverflow.com/questions/5652834/c-createprocess-wont-work-with-app-and-args-with-forward-slash-worked

... where someone said:

  "CreateProcess does work with forward-slashes on Windows 7. I'm guessing this is a version-specific feature (or bug)."

And here:

  https://www.reddit.com/r/programmingmemes/comments/1k8ctk2/comment/mp8lvsr/?utm_source=share&utm_medium=web3x&utm_name=web3xcss&utm_term=1&utm_content=share_button

Someone said: 

  "At least since Windows 2000, probably since always."

I asked an LLM, and got this:

  "That normalization is original to NT -- Windows NT 3.1 (1993). The kernel's RtlDosPathNameToNtPathName has always treated / as an alternate separator. CreateProcess
  itself never "added" the feature -- it just calls through to the kernel, which handles it transparently."

So I wonder whether what you're recalling is something from the Windows 9x days, which we no longer support (we support WinXP and up).  Do you happen to recall?

If it's really a problem on supported Windows versions, it should be a matter of converting back to forward slashes before we
call CreateProcess.  We already do that in gdb/windows-nat.c:windows_nat_target::create_inferior, for "set cwd":

      /* Mirror slashes on inferior's cwd.  */
      std::replace (expanded_infcwd.begin (), expanded_infcwd.end (),
		    '/', '\\');

we'd just need to do the same for exec_file.

Pedro Alves