SB2 Bug using std::filesystem

Platform Development
#1

Using std::filesystem operations in a program built in the SDK results in odd/incorrect file permissions.

Please see this minimal test case:
As you can see, test.out has only w permission, no r permission when copied with

std::filesystem::copy

In SDK:

    #include <filesystem>
    ​
    int main(int argc, char *argv[])
    {
    ​
        std::filesystem::path src(argv[1]);
        std::filesystem::path dst(argv[2]);
    ​
    ​
        std::error_code ec;
        std::filesystem::copy(src, dst, std::filesystem::copy_options::update_existing, ec);
    }
    [SailfishOS-4.6.0.11EA-aarch64] upstream # clang++ -std=c++17 test.cpp
    [SailfishOS-4.6.0.11EA-aarch64] upstream # ./a.out test.cpp test.out
    [SailfishOS-4.6.0.11EA-aarch64] upstream # ls -lh test.*
    -rw-r--r-- 1 1001 1001 256 Sep 19 15:43 test.cpp
    -rw-r--r-- 1 root root 256 Sep 19 15:46 test.out
    ​
    ​
    On Host:
    ​
    ╰ $ ls -lh test.*
    -rw-r--r-- 1 piggz piggz 256 Sep 19 16:43 test.cpp
    --w------- 1 piggz piggz 256 Sep 19 16:46 test.out
1 Like
#2

These are the syscalls made when the same program is run on my host (strace doesnt work in the sdk)

openat(AT_FDCWD, “test.cpp”, O_RDONLY|O_CLOEXEC) = 3
openat(AT_FDCWD, “test.out”, O_WRONLY|O_CREAT|O_EXCL|O_CLOEXEC, 0200) = 4
fchmod(4, 0100644) = 0
sendfile(4, 3, [0] => [184], 184) = 184
close(4) = 0
close(3) = 0

Maybe fchmod isnt implemented correctly?

1 Like
#3

When updating permissions using command line chmod within the sdk, permissions appear to update correctly, but on the host the remain the same. Becuase on the host there is no r permission, its not possible to cp a file within the sdk

[SailfishOS-4.6.0.11EA-aarch64] upstream # cp test.out test.2
cp: cannot open ‘test.out’ for reading: Operation not permitted
[SailfishOS-4.6.0.11EA-aarch64] upstream # ls -lh test.*
-rw-r–r-- 1 1001 1001 239 Sep 19 16:17 test.cpp
-rw----r-- 1 root root 239 Sep 19 16:24 test.out

1 Like
#4

@vige Just tagging you as this bug report isnt in the general bug reports category :slight_smile:

#5

Searching fchmod doesn’t yield good results on scratchbox2, maybe it is really not supported?

#6

Tagging @martyone or @Thaodan might be more effective :slight_smile: