================
@@ -122,8 +123,14 @@ struct ForkLaunchInfo {
ExitWithError(error_fd, "close");
break;
case FileAction::eFileActionDuplicate:
- if (dup2(action.fd, action.arg) == -1)
- ExitWithError(error_fd, "dup2");
+ if (action.fd != action.arg) {
----------------
labath wrote:
Can you explain your reasoning?
This is something I have considered, and I came to the opposite conclusion. The
reason is that I think this fits nicely into the `DuplicateFileAction(from,
to)` interface. You're saying "I want to take fd `from` from my process and
pass it as fd `to` to the child process". That statement makes sense regardless
of whether `from` and `to` have the same value or not. The fact that one needs
to use a different sequence of calls to achieve this effect is (can be) an
implementation detail.
Imagine I have some file descriptor open, and for whatever reason, I want to
pass it to the child process exactly as fd 47. That's something I can freely
do, as I control all of the FDs of the child process, but if this were to be
controlled by a separate flag, I would have to write special code to handle the
case where the my own copy of that FD happens to be 47:
```
if (fd_I_want_to_pass != 47)
info.AppendDuplicateFileAction(47, fd_I_want_to_pass);
else
info.InheritFileAction(47);
```
>From a windows point of view, I agree that a separate action makes sense, but
>if we can agree that the above makes sense for posix, then I think it also
>makes sense to reuse the same thing here (we're sort of doing the same thing,
>except that we only support the case where the two numbers are the same).
That said, since the `from==to` is going to be the only case that is going to
work in cross-platform code, I can imagine having some wrapper/helper function,
which lets you avoid specifying the same FD twice, but then calls
`DuplicateFileAction(fd, fd)` under the hood. Would that address your concerns?
https://github.com/llvm/llvm-project/pull/137978
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