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Title: bpo-34780: Fix potential hang during stdin initialization on Windows by izbyshev · Pull Request #9520 · python/cpython · GitHub

Open Graph Title: bpo-34780: Fix potential hang during stdin initialization on Windows by izbyshev · Pull Request #9520 · python/cpython

X Title: bpo-34780: Fix potential hang during stdin initialization on Windows by izbyshev · Pull Request #9520 · python/cpython

Description: On Windows, if there is an outstanding operation on a synchronous pipe handle (e.g., ReadFile()), many other operations will block until the first one completes. This is true even for operations that normally complete immediately (PeekNamedPipe(), SetFilePointer(), etc.). Python performs fstat(fd) during file object initialization to check for attempts to open a directory, which is forbidden. If fd refers to a pipe, msvcrt calls PeekNamedPipe() to fill in st_size member of struct stat, potentially hanging the interpreter before execution of user code when stdin object is initialized in the conditions described above. fstat() on Windows can't distinguish between a file and a directory because it relies on GetFileType(), which returns FILE_TYPE_DISK in both cases. Therefore, skipping the no-op check avoids the hang. https://bugs.python.org/issue34780

Open Graph Description: On Windows, if there is an outstanding operation on a synchronous pipe handle (e.g., ReadFile()), many other operations will block until the first one completes. This is true even for operations th...

X Description: On Windows, if there is an outstanding operation on a synchronous pipe handle (e.g., ReadFile()), many other operations will block until the first one completes. This is true even for operations th...

Opengraph URL: https://github.com/python/cpython/pull/9520

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