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Having various type declarations in the file.hrl file was once upon a time
necessary since the system could not really handle remote types. Now it can
and these declarations should not be there but appear in file.erl instead.
This means that files that need to use these types can refer to them using
a remote type reference, and not having to include file.hrl - at least not
for this reason.
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* ta/ensure_dir_eexist:
filelib_SUITE: strenghten tests of filelib:ensure_dir/1
Don't return a false {error,eexist} in filelib:ensure_dir/1
OTP-8389 Because of a race condition, using filelib:ensure_dir/1 from
multiple processes to create the same path or parts of the same
directory structure, filelib:ensure_dir/1 could return a
meaningless {error,eexist}. That race condition has been
eliminated, and {error,eexist} will now be returned only if there
exists a regular file, device file, or some other non-directory
file with the same name. (Thanks to Tuncer Ayaz.)
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This is about the non-atomicity of filelib:ensure_dir/1.
When using filelib:ensure_dir/1 from multiple processes to create
the same path or parts of the same directory structure (which happens
with rebar's worker processes) it happens quite a lot that between
a file:read_file_info/1 and file:make_dir/1 one of the other procs
has already created the directory we want to create.
mkdir(1) says one of the following for -p depending on which Unix
like system you're on:
"no error if existing"
"no error will be reported if a directory given as an operand already
exists"
I've seen more than one Erlang project where the return value of
ensure_dir/1 is ignored completely.
To eliminate the race condition, call file:make_dir/1 without first
testing whether the directory exists. If it succeeds everything
is fine. Otherwise, if the error code is {error,eexists}, check
whether the directory exists. If it does, everything is fine;
if not, return {error,eexist} (which indicates that there
exists a regular file with the same name, or (more unlikely)
that another process removed the directory after the call
to file:make_dir/1).
Signed-off-by: Tuncer Ayaz <[email protected]>
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