[llvm-bugs] [Bug 49526] New: "operation not permitted" ferror on recursive_directory_iterator despite skip_permission_denied

[via llvm-bugs]

https://bugs.llvm.org/show_bug.cgi?id=49526

            Bug ID: 49526
           Summary: "operation not permitted" ferror on
                    recursive_directory_iterator despite
                    skip_permission_denied
           Product: libc++
           Version: unspecified
          Hardware: All
                OS: All
            Status: NEW
          Severity: normal
          Priority: P
         Component: All Bugs
          Assignee: unassignedclangbugs at nondot.org
          Reporter: ssh at pobox.com
                CC: llvm-bugs at lists.llvm.org, mclow.lists at gmail.com

On POSIX filesystem backend type systems the
std::filesystem::recursive_directory_iterator throws a filesystem_error
exception with "operation not permitted" when the opendir/readdir call returns
EPERM instead of EACCES even if
std::filesystem::directory_options::skip_permission_denied is set.

Given the following code:

#include <iostream>
#include <filesystem>

int main(int argc, char* argv[])
{
    fs::path dir{"."};
    if(argc == 2) {
        dir = fs::u8path(argv[1]);
    }

    int totalDirs = 0;
    int totalFiles = 0;
    try {
        for(const auto& de : fs::recursive_directory_iterator(dir,
fs::directory_options::skip_permission_denied)) {
            if(de.is_regular_file()) {
                ++totalFiles;
            }
            else if(de.is_directory()) {
                ++totalDirs;
            }
        }
    }
    catch(fs::filesystem_error fe) {
        std::cerr << "Error: " << fe.what() << std::endl;
        exit(1);
    }
    std::cout << totalFiles << " files in " << totalDirs << " directories" <<
std::endl;
    return 0;
}

This fails for example on macOS when called on the user home directory with:

Error: filesystem error: in recursive_directory_iterator::operator++():
attempting recursion into "/Users/<user>/Library/Application
Support/MobileSync": Operation not permitted

This is due to System Integrity Protection (since macOS 10.14) on that folder
leading to EPERM.

On Linux, called with / it stops when hitting for example a
"/proc/1/task/1/cwd", resulting in EPERM too.

I don't have examples from other POSIX systems, but I would say handling only
EACCES  for the skip_permission_denied option is not enough.

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