fs::File::create() on Unix should use 0666 mode by default.

[rodrigorc]

Compare the output of this rust code

fn main() {
    std::fs::File::create("test1.txt");
}

with the C equivalent:

int main() { fopen("test2.txt", "w"); }

or the C++ one:

#include <fstream>
int main() { std::ofstream f("test3.txt"); }

The output of these programs is:

$ (compile & run)
$ ls -l test?.txt
-rw------- 1 rodrigo rodrigo 0 Feb 11 12:00 test1.txt
-rw-r--r-- 1 rodrigo rodrigo 0 Feb 11 12:00 test2.txt
-rw-r--r-- 1 rodrigo rodrigo 0 Feb 11 12:00 test3.txt

The C and C++ versions will create a file with mode 0666 (minus the umask, mine is 0022). But the Rust one is different: 0600.

Given the Principle of Least Surprise, I think that the default mode should be changed from 0600 to 0666.

[GuillaumeGomez]

There is no direct equivalent in C. However, it doesn't seem a good idea to give a create function without forcing the user to give permission. I think a change on that should be done (I think I'll right a RFC to change that).

[rodrigorc]

I don't understand why you think my C code is not equivalent. fopen() is the most C-ish way of creating files. Maybe you are thinking of open() but that is the POSIX way, not the C one.

Let me cite "man 3 fopen":

Any created files will have mode S_IRUSR | S_IWUSR | S_IRGRP | S_IWGRP | S_IROTH | S_IWOTH (0666), as modified by the process's umask value (see umask(2)).

About forcing the user to set permission (open() does that), but fopen() does just fine without any mechanism to set permissions at all. It could be a good idea anyway, but remember that in Windows the permissions work quite differently, so maybe there is no easy equivalent.

[alexcrichton]

Yes I think that this change was just carried over from the previous implementation. The relevant line to change would be this one and I think it's fine to make the change.

[GuillaumeGomez]

Then I change it.

[alexcrichton]

Fixed in #22186