boost filesystem create_directories function fails randomly when accessing to a mapped network drive

[sergio.anza@…]

When trying to create a folder in a mapped network drive with boost filesystem create_directories function, I get random errors of type: "The system cannot find the path specified.". By random I mean that sometimes I get the error and sometimes I don't.

And yes, I have checked:

• It is a valid path.
• It is not a too long path. In fact, I use windows extended path as \?\PATH.
• The network drive works perfectly, and it is inside our company local network (Gigabit ethernet).
• I have write permissions.
• There are not unicode characters.

Below the code (adapted to make it more simple).

#include "boost/filesystem.hpp"
#include <string>
#include <chrono>
#include <thread>
#include <iostream>

#define MAX_RETRIES 10
#define RETRY_TIME 5000 //in millisecond

namespace fs = boost::filesystem;

bool createDirectory(const std::string& folderPath)
{        
    //If the function does not succeed to create the directory in first place, it will retry after RETRY_TIME miliseconds a maximum number of MAX_RETRIES.
    for (unsigned int i=0; i<MAX_RETRIES; i++)
    {
        try
        {
            if (fs::create_directories(fs::path(folderPath)))
            {   
                std::cerr << "Folder created successfully!" << std::endl;             
                return true;
            }
        }
        catch (fs::filesystem_error const & e)
        {
                std::cerr << "File operation problem with files: " << e.what() <<". Try number: "<<i+1<<std::endl;
        }

        if (i==MAX_RETRIES-1)
        {
            return false;
        }

        std::this_thread::sleep_for(std::chrono::milliseconds(RETRY_TIME)); 

    }
    return true;
}

In this example I am trying to create the folder:

Z:\PRIVATE_FOLDERS\XXX\tests\YYY\ZZZZZ\MMMMMMM\CCCCCC\@mmmm1\@ccccc1\@eeeeeeeee2 (Z is a network mapped drive):

And here is the output. Sometimes it works the first time

Folder created successfully!

Sometimes it fails several consecutive times until it works. Magic?

File operation problem with files: "boost::filesystem::create_directories: The system cannot find the path specified: "\\?\Z:\PRIVATE_FOLDERS\XXX\tests\YYY\ZZZZZ\MMMMMMM\CCCCCC\@mmmm1\@ccccc1\@eeeeeeeee2"". try number: 1
File operation problem with files: "boost::filesystem::create_directories: The system cannot find the path specified: "\\?\Z:\PRIVATE_FOLDERS\XXX\tests\YYY\ZZZZZ\MMMMMMM\CCCCCC\@mmmm1\@ccccc1\@eeeeeeeee2"". try number: 2
File operation problem with files: "boost::filesystem::create_directories: The system cannot find the path specified: "\\?\Z:\PRIVATE_FOLDERS\XXX\tests\YYY\ZZZZZ\MMMMMMM\CCCCCC\@mmmm1\@ccccc1\@eeeeeeeee2"". try number: 3
Folder created successfully!

The problem of this implementation is that, a priori there is no way to differentiate if the input path is a network drive, or it is a wrong path or does not have write permissions. Therefore I need always to spend the MAX_RETRIES until it finally fails, with the consequent performance penalty.

Notes:

• I am on Windows 10
• Boost version is 1.60 built on VS2015 downloaded from official webpage.
• I use intel compiler 17 for the rest of the code.