[Lldb-commits] [lldb] [lldb/Host] Enable inheriting "non-inheritable" FDs (PR #126935)

[David Spickett via lldb-commits]

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@@ -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) {
+        if (dup2(action.fd, action.arg) == -1)
+          ExitWithError(error_fd, "dup2");
+      } else {
+        if (fcntl(action.fd, F_SETFD,
+                  fcntl(action.fd, F_GETFD) & ~FD_CLOEXEC) == -1)
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DavidSpickett wrote:

...definitely "it's the same picture" if you don't look too deep into it.

* New process is started, and is given some file descriptors.
* It sets CLOEXEC on those.
* It then runs the code this PR is modifying.
* That code clears CLOEXEC from the file descriptor in question, so that it can live through the execve.
* It execve's into whatever other program.
* From this point on, that file descriptor will never have CLOEXEC set on it, unless something in this new program does that.
* So we can execve any number of times and the file descriptor will always survive.

Which sounds vaguely like a "leak" to me, if you do indeed execve multiple times. But maybe this is the intended behaviour?

https://github.com/llvm/llvm-project/pull/126935