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@node mmap
@section @code{mmap}
@findex mmap
POSIX specification:@* @url{https://pubs.opengroup.org/onlinepubs/9699919799/functions/mmap.html}
Gnulib module: ---
Portability problems fixed by Gnulib:
@itemize
@end itemize
Portability problems not fixed by Gnulib:
@itemize
@item
This function is missing on some platforms:
mingw, MSVC 14.
@item
On platforms where @code{off_t} is a 32-bit type, this function may not
work correctly across the entire data range of files larger than 2 GB.
The fix is to use the @code{AC_SYS_LARGEFILE} macro.
@item
To get anonymous memory, on some platforms, you can use the flags
@code{MAP_ANONYMOUS | MAP_PRIVATE} and @code{-1} instead of a file descriptor;
on others you have to use a read-only file descriptor of @file{/dev/zero}.
@item
On HP-UX, passing a non-NULL first argument, as a hint for the address (even
without @code{MAP_FIXED}), often causes @code{mmap} to fail. Better pass NULL
in this case.
@item
On HP-UX, @code{MAP_FIXED} basically never works. On other platforms, it depends
on the circumstances whether memory can be returned at a given address.
@end itemize
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