How to convert errno to exception using <system_error>
You are on the right track, just pass the error code and a std::generic_category
object to the std::system_error
constructor and it should work.
Example:
#include <assert.h>
#include <errno.h>
#include <iostream>
#include <system_error>
int main()
{
try
{
throw std::system_error(EFAULT, std::generic_category());
}
catch (std::system_error& error)
{
std::cout << "Error: " << error.code() << " - " << error.what() << '\n';
assert(error.code() == std::errc::bad_address);
}
}
Output from the above program on my system is
Error: generic:14 - Bad address
To add to the excellent accepted answer, you can enrich the error message with some contextual information in the 3rd argument, e.g. the failing file name:
std::string file_name = "bad_file_name.txt";
fd = open(file_name, O_RDWR);
if (fd < 0) {
throw std::system_error(errno, std::generic_category(), file_name);
}
Then when caught, e.what()
will return, for example:
bad_file_name.txt: file not found