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10.206 dup2

POSIX specification:
https://pubs.opengroup.org/onlinepubs/9699919799/functions/dup2.html

Gnulib module: dup2

Portability problems fixed by Gnulib:

• This function is declared in a different header file (namely, <io.h>) on some platforms: MSVC 14.
• This function always returns 0 for success on some platforms: mingw, MSVC 14.
• This function can hang when duplicating an fd to itself on some platforms: mingw, MSVC 14.
• This function crashes when invoked with invalid arguments on some platforms: Cygwin 1.7.17, MSVC 14.
• This function crashes when invoked with valid arguments on some platforms: Cygwin 1.7.25.
• This function fails with EINVAL when duplicating an fd to itself: Android.
• This function resets the FD_CLOEXEC flag when duplicating an fd to itself on some platforms: Haiku.
• This function returns 0 for dup2 (1, 1) on some platforms: Cygwin 1.5.x.
• This function may return -EBADF instead of -1 on some platforms: Linux releases between July 2008 and May 2009 (versions 2.6.27 to 2.6.29).
• This function returns EMFILE instead of EBADF for large targets, which interferes with using dup2(fd,fd)==fd) as the minimal EBADF filter: AIX 7.1, FreeBSD 6.1, Cygwin 1.5.

Portability problems not fixed by Gnulib: