I am trying to unmount a usb-storage device through a c++ code as follows.
while(umount("/dev/sdc1/")!=0)
{
std::cout << "ERROR: " << strerror(errno) << std::endl;
std::this_thread::sleep_for (std::chrono::seconds(2));
}
But, I get an error saying: Invalid argument.
What am I doing wrong?
Thanks in advance!
Related
While using a class to hold my window class and Vulkan class, this error VK_ERROR_FEATURE_NOT_PRESENT is returned when I use vkCreateDevice however, when I put the same code the class is running into the main class, it works completely fine. I also had a similar problem with getting the instance extensions via SDL_Vulkan_GetInstanceExtensions.
working main.cpp
window.createWindow();
engine.window = window.window;
try {
engine.initialize();
}
catch (XiError error) {
std::cout << "Error " << error.code << ": " << error.definition << std::endl;
}
window.instance = engine.getVkInstance();
VkPhysicalDeviceProperties deviceProperties;
vkGetPhysicalDeviceProperties(engine.physicalDevice, &deviceProperties);
std::cout << deviceProperties.deviceName << ", Driver Version " << deviceProperties.driverVersion << std::endl;
try {
window.createSurface();
}
catch (XiError error) {
std::cout << "Error " << error.code << ": " << error.definition << std::endl;
}
window.mainLoop();
vkDestroyDevice(engine.logicalDevice, nullptr);
vkDestroySurfaceKHR(engine.instance, window.surface, nullptr);
vkDestroyInstance(engine.instance, nullptr);
SDL_DestroyWindow(window.window);
SDL_Quit();
not working main.cpp
try {
app.run();
}
catch (XiError error) {
std::cout << "Error " << error.code << ": " << error.definition << std::endl;
}
VkPhysicalDeviceProperties deviceProperties;
vkGetPhysicalDeviceProperties(app.engine.physicalDevice, &deviceProperties);
std::cout << deviceProperties.deviceName << ", Driver Version " << deviceProperties.driverVersion << std::endl;
app.window.mainLoop();
app.shutDown();
app.run()
window.createWindow();
engine.window = window.window;
engine.createVulkanInstance();
window.instance = engine.getVkInstance();
window.createSurface();
engine.getPhysicalDevices();
engine.selectPhysicalDevice();
engine.createLogicalDevice();
window.mainLoop();
app.shutDown()
vkDestroyDevice(engine.logicalDevice, nullptr);
vkDestroySurfaceKHR(engine.instance, window.surface, nullptr);
vkDestroyInstance(engine.instance, nullptr);
SDL_DestroyWindow(window.window);
SDL_Quit();
window engine and app are pre-defined by my own classes
I've tried manually adding the different required and supported extensions, and it works, but it feels hacky and is quite a large bulk of code. If this is a weird out of scope error, I've really no idea. if any other code is needed I'll be happy to provide it and the GitHub can also be found here: https://github.com/XiniaDev/Xinia-Engine
I think your problem is that requiredFeatures in XiEngine is not initialised. You set a few values to true, but I think you need a memset(&requiredFeatures, 0, sizeof(requiredFeatures)); or similar at the start of XiEngine::XiEngine to fix it.
I'm attempting to decode .gif files using giflib. The following code leads to a segfault on the final line (the output width/height is correct).
GifFileType* gif = DGifOpenFileName(filename.c_str(), &errCode);
if (gif == NULL) {
std::cout << "Failed to open .gif, return error with type " << errCode << std::endl;
return false;
}
int slurpReturn = DGifSlurp(gif);
if (slurpReturn != GIF_OK) {
std::cout << "Failed to read .gif file" << std::endl;
return false;
}
std::cout << "Opened .gif with width/height = " << gif->SWidth << " " << gif->SHeight << std::endl;
std::cout << gif->SavedImages[0].RasterBits[0] << std::endl;
Output:
Opened .gif with width/height = 921 922
zsh: segmentation fault (core dumped) ./bin/testgiflib
As I understand, giflib should populate gif->SavedImages. But it is NULL after calling DGifSlurp().
Any ideas would be appreciated.
EDIT
I've added the following lines of code following a suggestion in comments:
if (gif->SavedImages == NULL) {
std::cout <<"SavedImages is NULL" << std::endl;
}
The line is printed, indicating that SavedImages is NULL.
EDIT2
Some gifs on which this issue occurs (note that I can't get it to work on any gifs):
https://upload.wikimedia.org/wikipedia/en/3/39/Specialist_Science_Logo.gif
GIF image data, version 89a, 921 x 922
https://upload.wikimedia.org/wikipedia/commons/2/25/Nasa-logo.gif
GIF image data, version 87a, 1008 x 863
Preface: Looks like in my version of giflib, 4.1.6, the DGifOpenFileName() function takes only the filename parameter, and does not return an error code, which is an irrelevant detail.
After adjusting for the API change, and adding the necessary includes, I compiled and executed the following complete, standalone test program:
#include <gif_lib.h>
#include <iostream>
int main()
{
GifFileType* gif = DGifOpenFileName("Specialist_Science_Logo.gif");
if (gif == NULL) {
std::cout << "Failed to open .gif, return error with type " << std::endl;
return false;
}
int slurpReturn = DGifSlurp(gif);
if (slurpReturn != GIF_OK) {
std::cout << "Failed to read .gif file" << std::endl;
return false;
}
std::cout << "Opened .gif with width/height = " << gif->SWidth << " " << gif->SHeight << std::endl;
std::cout << (int)gif->SavedImages[0].RasterBits[0] << std::endl;
}
Except for the presence of the header files, the slightly different DGifOpenFilename() signature, and my tweak to cast the second output line's value to an explicit (int), this is identical to your code. Also, the code was changed to explicitly open the Specialist_Science_Logo.gif file, one of the GIF image files you were having an issue with.
This code executed successfully on Fedora x86-64, giflib 4.1.6, gcc 5.5.1, without any issues.
Instrumenting the sample code with valgrind did not reveal any memory access violations.
From this, I conclude that there is nothing wrong with the shown code. The shown code is obviously an excerpt from a larger application. The bug lies elsewhere in this application, or perhaps giflib itself, and only manifests here.
I was wondering if there's a way to get an string representation of an errors type/name from std::exception. Let's say I catch std::exception &err, is there a way to say something like err.getName() or err.getType(). I have a project that can throw a wide variety of errors, but I want to get the exact type if it has not been caught by something else. I'll show what I generally mean.
For simplicity sake, let's say libraryA has several uniquely defined exception types (libraryA::Exception_# where # is replaced by a number to uniquely identify the error).
Here's some simple code for this:
try{
doSomeTaskThatMightThrowAnError();
}catch(libraryA::Exception_1 &err){
std::cout << "Error type 1: " << err.what() << std::endl;
}catch(libraryA::Exception_2 &err){
std::cout << "Error type 2: " << err.what() << std::endl;
}catch(libraryA::Exception_3 &err){
std::cout << "Error type 3: " << err.what() << std::endl;
}catch(std::exception &err){
std::cout << "Unknown error: " << err.what() << std::endl;
}
Is there some way within catch(std::exception &err)'s block that I can say std::cout << "Unknown error type: " << err.getType() << '\n' << "Error message: " << err.what() << std::endl;
I want to catch std::exception as a precaution in case nothing else catches the error, but I want to be able to identify the exact error type so I may update my code and include another catch statement for it. Is this possible?
You can always use typeid(e).name() (remember to include <typeinfo> header).
But very little is guaranteed about the name so produced.
With Visual C++ it's nice and readable, with g++ it's mangled so that you practically need to use some compiler-specific functionality to demangle it.
I'm catching errors in Boost Asio program like
if (!error)
{
//do stuff
}
else
{
std::cout << "Error : " << error << std::endl;
//handle error
}
But the error isn't human-readable (e.g. connecting to SSL server without certificate gives error asio.ssl:335544539). Is there any better way how to display error ?
If you are likely using boost::system::error_code you can call:
error.message()
to get a more human-friendly message.
Using operator<< translates into:
os << ec.category().name() << ':' << ec.value()
Here you can check a detailed overview of the available members in error_code.
I am currently catching errors from boost::filesystem::is_directory and showing the error to the user by calling "what()" on the exception. This gives the reason for failure but the error is strange to the user. For example:
boost::filesystem::is_directory: Access is denied
How can I catch the boost error and figure out what the actual cause is, so I can show a nicer error message?
By "nicer error message" would you mean something like
#include <iostream>
#include <boost/filesystem.hpp>
int main()
{
boost::filesystem::path p("/proc/1/fd/1");
try {
boost::filesystem::is_directory(p);
} catch(const boost::filesystem::filesystem_error& e)
{
if(e.code() == boost::system::errc::permission_denied)
std::cout << "Search permission is denied for one of the directories "
<< "in the path prefix of " << p << "\n";
else
std::cout << "is_directory(" << p << ") failed with "
<< e.code().message() << '\n';
}
}