I've been a C++ developer since it arrived. All was on windows, and I haven't touched it in about 6 years.
Now I'm trying to get an old code-base working using VS Code on my Mac. I'm using clang++ with c++17.
This problem is vexing; I've seen many other posts with the same issue, but the problem always seemed to be something in the code.
Note: this code worked fine with C++11 on Windows.
To simplify, I copied the code to execute right at the top of main. Here is is:
ifstream file("assets/textures/blocks.txt", ios::in);
if( file.is_open() ) {
string s;
getline(file, s); // <-- This line causes the error.
cout << s << endl;
}
As this code worked elsewhere, I assume I've got a setup or environment problem and am looking for hints towards what to check on.
Thank you for any help!
An update:
Thank you. I paired the program down and tried a few things. Here's the deal:
If I leave all my files to be compiled, but replace main.cpp with the below code, the cout line generates the same exception.
If I cull all the unused files, the code works.
Something in some other file is somehow breaking the stream code. I'm clueless.
#include <iostream>
#include <istream>
using namespace std;
int main() // int argc, char** argv)
{
cout << "Hello World" << endl;
}
I should add: this is a GLFW 3D game engine app. It does not subclass or interact with any stream in any way other than the most basic file read/write operations.
Related
I have a weird problem when trying to print out the content of a vector.
I'm using Visual Studio Code with the CMake extension.
I can print out simple text using cout
#include <iostream>
#include <vector>
using namespace std;
int main() {
cout << "test" << endl;
return 0;
}
But I can't print out the vectors content
#include <iostream>
#include <vector>
using namespace std;
int main() {
vector<int> test = {1,2,3};
cout << "test" << endl;
cout << test[1] << endl;
return 0;
}
I've never really worked with C++ vectors, so I'm probably missing something fairly obvious but I followed a C++ vector tutorial step by step and for them, the output works fine.
Cheers,
Luca
I'm new to C++ and have exactly the same problem.
Temporary workaround as posted by Luckylone here
would be to copy libstdc++-6.dll from your mingw64\bin folder into your project folder.
Something is messing up our link with the resources even though folders are properly added to system PATH.
EDIT: After an afternoon of troubleshooting, I've solved my problem by uninstalling compilers (originally provided through WinLibs) and reinstalling them using MSYS2.
Delete the existing Mingw64 folder, remove the PATH variables, then carefully follow these instructions. Keep in mind that I had to add mingw64/bin to both user and system Path, and restart VS Code before damn std::vector finally started to print.
I just installed mingw on my Windows 10 computer and wanted to code a program that read two files. I immediately faced a frustrating bug with ifstream: when I declare more than one ifstream, the program seems to crash (nothing is logged although the first line cout some text).
The following code compiles and logs "test" in the console:
#include <iostream>
#include <fstream>
using namespace std;
int main()
{
cout << "test" << endl;
ifstream test;
return 0;
}
The following code compiles but seems to crash at runtime, nothing is logged:
#include <iostream>
#include <fstream>
using namespace std;
int main()
{
cout << "test" << endl;
ifstream test;
ifstream test2;
return 0;
}
I tested the exact same codes on a macOS Mojave and both codes work and log "test".
I guess the issue is related to the g++ installation but I'd like to know what's really happening and how I can fix this on Windows.
I'm following some C++ tutorials and have started experimenting with structures, however a test structure I built is not behaving as intended. I have tried running it a few times and all it outputs is (11db), and when I try rerunning it I get a window saying that the product is already running.
Here is the code...
#include <iostream>
using namespace std;
int main(){
struct Address {
int streetNum;
string streetName;
};
Address myHouse;
myHouse.streetNum = 911;
myHouse.streetName = "Inverness Street";
cout << myHouse.streetName << endl;
return 0;
}
I would expect the output to be "Inverness Street". Why am I getting an error instead?
EDIT ** Bonus points for anyone who can tell me how to remove a missing file warning? I removed a useless file that was created as a means to find my way around creating different types of files, but since I deleted it I have had a warning in the file that it once shared a folder with.
Picking up C++ and having a go at it on OS X 10.9 using XCode 5.0.2 and using Alex Allain as reference.
The following code compiles just fine and outputs correctly
#include <iostream>
#include <string>
using namespace std;
int main()
{
std::string user_first_name = "test";
std::cout << user_first_name << "\n";
return 0;
}
When I add a getline function, code appears to compile but with no output.
#include <iostream>
#include <string>
using namespace std;
int main()
{
std::string user_first_name = "test";
std::getline( std::cin, user_first_name, '\n' );
std::cout << user_first_name << "\n";
return 0;
}
In fact debug navigator has memory filling up with bars (although actual memory use is fixed at 276 KB). Why am I getting stumped on such a simple thing/concept?
I did a bit of digging around and its quite likely this is related to a text encoding issue. I'm using defaults which is Unicode (UTF-8). Encoding is not something I'm familiar with, never something I had to deal with when learning on Windows. How do I get past this?
I can't comment regarding the use of XCode or OS X, but it was my understanding that std::cin always gives you a narrow (single-byte) character stream. In Windows (at least with Visual Studio), I think it works whether you compile for UTF8 (single-byte for all ASCII characters) or UTF16 (2-bytes for all ASCII characters). The runtime library presumably does the conversion for you as necessary.
I'm not sure what "filling up with bars" means, but maybe it's just that you're looking at uninitialized memory. If you think that it is an encoding issue, perhaps try using wstring/wcin instead of string/cin and see if that helps.
I know there's been a handful of questions regarding std::ifstream::open(), but the answers didn't solve my problem. Most of them were specific to Win32, and I'm using SDL, not touching any OS-specific functionality (...that's not wrapped up into SDL).
The problem is: std::ifstream::open() doesn't seem to work anymore since I've switched from Dev-C++ to Code::Blocks (I've been using the same MinGW-GCC back-end with both), and from Windows XP to Vista. (It also works perfectly with OS X / xcode (GCC back-end).)
My project links against a static library which #includes <string>, <iostream>, <fstream> and <cassert>, then a call is made to functionality defined in the static library, which in turn calls std::ifstream::open() (this time, directly). Following this, the stream evaluates to false (with both the implicit bool conversion operator and the good() method).
Code:
#include "myStaticLibrary.hpp"
int main(int argc, char **argv)
{
std::string filename("D:/My projects/Test/test.cfg");
std::cout << "opening '" << filename << "'..." << std::endl;
bool success(false);
// call to functionality in the static library
{
std::ifstream infile(filename.c_str());
success = infile.good();
// ...
}
// success == false;
// ...
return 0;
}
stdcout.txt says:
opening 'D:/My projects/Test/test.cfg'...
When I open stdcout.txt, and copy-paste the path with the filename into Start menu / Run, the file is opened as should be (I'm not entirely sure how much of diagnostic value this is though; also, the address is converted to the following format: file:///D:/My%20projects/test/test.cfg).
I've also tried substituting '/'s with the double backslash escape sequence (again, slashes worked fine before), but the result was the same.
It is a debug version, but I'm using the whole, absolute path taken from main()'s argv[0].
Where am I going wrong and what do I need to do to fix it?
Please create a minimal set that recreates the problem. For example, in your code above there's parsing of argv and string concatentation, which do not seem like a necessary part of the question. A minimal set would help you (and us) see exactly what's going wrong, and not be distracted by questions like "what's GetPath()?".
Try to do this instead of assert(infile.good()):
assert(infile);
I have overseen the importance of the fact that the function in question has close()d the stream without checking if it is_open().
The fact that it will set the stream's fail_bit (causing it to evaluate to false) was entirely new to me (it's not that it's an excuse), and I still don't understand why did this code work before.
Anyway, the c++ reference is quite clear on it; the problem is now solved.
The following code:
#include <string>
#include <iostream>
#include <fstream>
#include <assert.h>
using namespace std;;
int main(int argc, char **argv)
{
std::string filename("D:/My projects/Test/test.cfg");
std::cout << "opening '" << filename << "'..." << std::endl;
std::ifstream infile(filename.c_str());
assert(infile.good()); // fails
return 0;
}
works fine on my Windows system using MinGW g++ 4.4.0, if I create the required directory structure. Does the file test.cfg actually exist? If you are opening a stream for input, it wioll fail if the file is not there.
Edit: To remove any DevC++ to CB issues:
build using command line only
make sure you rebuild the static library too