In this section, we’ll address some of the common issues that new programmers seem to run across with fairly high probability. This is not meant to be a comprehensive list of compilation or execution problems, but rather a pragmatic list of solutions to very basic issues. If you have any suggestions for other issues that might be added to this list, post them in the comments section below.
General run-time issues
Q: When executing a program from the IDE, the console window blinks and then closes immediately.
First, add or ensure the following lines are near the top of your program (Visual Studio users, make sure these appear after #include “pch.h” or #include “stdafx.h”, if those exist):
|
1 2 |
#include "iostream" #include "limits" |
Second, add the following code at the end of your main() function (right before the return statement):
|
1 2 3 |
std::cin.clear(); // reset any error flags std::cin.ignore(std::numeric_limits<std::streamsize>::max(), '\n'); // ignore any characters in the input buffer until we find an enter character std::cin.get(); // get one more char from the user |
This will cause your program to wait for the user to press a key before continuing, which will give you time to examine your program’s output before your compiler closes the console window.
Other solutions, such as the commonly suggested system(“pause”) solution may only work on certain operating systems and should be avoided.
Q: I ran my program and get a window but no output.
Your virus scanner or anti-malware may be blocking execution. Try disabling it temporarily and see if that’s the issue.
Q: My program compiles but it isn't working correctly. What do I do?
Debug it! There are tips on how to diagnose and debug your programs later in chapter 1 or 2.
General compile-time issues
Q: When I compile my program, I get an error about unresolved external symbol _main or _WinMain@16
This means your compiler can’t find your main() function. All programs must include a main() function.
There are a few things to check:
a) Does your code include a function named main?
b) Is main spelled correctly?
c) When you compile your program, do you see the file that contains function main() get compiled? If not, either move the main() function to one that is, or add the file to your project (see lesson 1.8 -- Programs with multiple files for more information about how to do this).
d) Did you create a console project? Try creating a new console project.
Q: I'm trying to use C++11/14/17/XX functionality and it doesn't work
If your compiler is old, it may not support these more recent additions to the language. In that case, upgrade your compiler.
Alternatively, you can try seeing if your compiler has support for these but has it turned off by default. For GCC/G++, you can try passing compiler flags -std=c++11, -std=c++14, or -std=c++17. For Code::Blocks, make sure the appropriate global compiler setting is set. We show how to do that in lesson 0.6 -- Installing an Integrated Development Environment (IDE).
Q: When trying to use cin, cout, or endl, the compiler says cin, cout, or endl is an 'undeclared identifier'
First, make sure you have included the following line near the top of your file:
|
1 |
#include "iostream" |
Second, make sure each use of cin, cout, and endl are prefixed by “std::”. For example:
|
1 |
std::cout << "Hello world!" << std::endl; |
If this doesn’t fix your issue, then it may be that your compiler is out of date, or the install is corrupted. Try reinstalling and/or upgrading to the latest version of your compiler.
Q: When trying to use endl to end a printed line, the compiler says end1 is an 'undeclared identifier'
Make sure you do not mistake the letter l (lower case L) in endl for the number 1. endl is all letters. Make sure your editor is using a font that makes clear the differences between the letter lower case L, upper case i, and the number 1. Also the letter capital o and the number zero can easily be confused in many non-programming fonts.
Visual Studio issues
Q: When compiling with Microsoft Visual C++, you get a C1010 fatal error, with an error message like "c: cprojects est.cpp(263) :fatal error C1010: unexpected end of file while looking for precompiled header directive"
This error occurs when the Microsoft Visual C++ compiler is set to use precompiled headers but one (or more) of your C++ code files does not #include “stdafx.h” or #include “pch.h” as the first line of the code file.
Our suggested fix is to turn off precompiled headers, which we show how to do in lesson 0.9 -- Configuring your compiler: Build configurations.
If you would like to keep precompiled headers turned on, to fix this problem, simply locate the file(s) producing the error (in the above error, test.cpp is the culprit), and add the following line at the very top of the file(s):
|
1 |
#include "pch.h" |
Older versions of Visual Studio use “stdafx.h” instead of “pch.h”, so if pch.h doesn’t resolve the issue, try stdafx.h.
Note that for programs with multiple files, every C++ code file needs to start with this line.
Alternatively, you can turn off precompiled headers.
Q: Visual Studio gives the following error: "1MSVCRTD.lib(exe_winmain.obj) : error LNK2019: unresolved external symbol _WinMain@16 referenced in function "int __cdecl invoke_main(void)" (?invoke_main@@YAHXZ)"
You’ve likely created a Windows graphical application rather than a console application. Recreate your project, and make sure to create it as a Windows (or Win32) Console project.
Q: When I compile my program, I get a warnings about "Cannot find or open the PDB file"
This is a warning, not an error, so it shouldn’t impact your program. However, it is annoying. To fix it, go into the Debug menu -> Options and Settings -> Symbols, and check “Microsoft Symbol Server”.
Something else
Q: I have some other problem that I can't figure out. How can I get an answer quickly?
As you progress through the material, you’ll undoubtedly have questions or run into unexpected problems. What to do next depends on your problem. But in general, there are a few things you can try.
First, ask Google. Find a good way to phrase your question and do a Google search. If you have received an error message, paste the exact message into google using quotes.
Odds are someone has already asked the same question and there is an answer waiting for you.
If that fails, ask on a Q&A board. There are websites designed for programming questions and answers, like Stack Overflow. Try posting your question there. Remember to be thorough about what your problem is, and include all relevant information like what OS you’re on and what IDE you’re using.
 0.9 -- Configuring your compiler: Build configurations
|
 Index
|
 0.7 -- Compiling your first program
|
Some time ago I noticed that every time I want to build a file, I receive a message "error: cannot find 'ld'". I hadn't had any similar problem before (I mean, I did some examples from lessons and didn't notice this message; everything worked perfectly).
I only found an information that it could be a problem with an 'ld.exe' file. Is that true?
Thanks in advance.
Yes, most likely related to ld executable. Ld is the GNU linker that links object files created with gcc/g++. If your programs compiled and ran, I guess I'd ignore the issue for now, because your code must be getting linked somehow...
Hello, I'd like to inquire about a certain problem I'm having while using visual studio 2017.
When I compile, build and run the program for the first time, or any other time with no changes, it runs without any issues. If I try to add or remove code or make any changes and try to compile, it gives me an error saying it cannot open filename.exe at the debug folder of the project so it could write in it. I've found the quickest solution to solving this would be deleting the exe file, but that's not efficient in any way. I read some saying AV might be causing this problem but I don't have any heavily active ones to give me such a problem, or I take a look at the processes and I don't see any CMDs open, so I don't know how to solve this permanently. Help would be greatly appreciated.
Also, I'd like to say, having taken courses on Java in my university till OOP, I have some insight into basics of programming and such. I want to say, this course is amazing so far, really well done and I'm loving it so far.
I was able to solve this issue (about friggin time) by starting the Application Experience service, besides some other solutions some people have, this is the one that worked for me.
Hi Alex, Thanks for the information i have learnt a lot from reading this.
ello, Alex! I have Windows 10 and CodeBlocks. My CodeBlocks sayed that he dosen't find the GNU GCC Compiler.
What can i do? Please, help me!
Did you install the MinGW version of Code::Blocks?
Hi Alex.
Could you please explain what's wrong with this program I've done.
#include "stdafx.h"
#include <iostream>
//#include "multiply.h"
int mul(int a, int b)
{
return a * b;
}
int main()
{
int x;
int y;
std::cout << "enter first number" << std::endl;
std::cin >> x;
std::cout << "enter second number" << std::endl;
std::cin >> y;
std::cout << mul(x, y) << std::endl;
return 0;
}
1>------ Build started: Project: My own try, Configuration: Debug Win32 ------
1>multiply a.cpp
1>c:\progaming\my own try\my own try\multiply a.cpp(1): fatal error C1010: unexpected end of file while looking for precompiled header. Did you forget to add '#include "stdafx.h"' to your source?
1>My own try.cpp
1>Generating Code...
1>Done building project "My own try.vcxproj" -- FAILED.
========== Build: 0 succeeded, 1 failed, 0 up-to-date, 0 skipped ==========
Hi Yitzi!
Disable precompiled headers in your project settings and remove the include to stdafx.h.
Hello,
Im coming across a issue while trying to build my program. error C2679. And I cant figure out a solution can someone help me?
Hi William!
Post your source code.
Hi,
In our textbook it says that we have to use "using namespace std;", but I read somewhere that it can cause name collisions, but I don't know what it means; so is it better to use "using namespace std;" or std::cout, std::cin , std::endl; ,etc ? Can you replace std inside "using namespace std" with other codes?
Thanks.
Hi Mark!
Don't use 'using namespace', if your book tells you to use it you might want to consider getting a new book, because there might be more bad advise in there.
Example naming colission:
You might not be able to understand this example just yet. Your question should resolve itself in future lessons.
References
* Lesson 4.3b - Namespaces
Thanks.
Can you help me?
I just downloaded visual studio and I typed this code:
but I get a lot of errors and I don't know why this ar the errors:
Severity Code Description Project File Line Suppression State
Error (active) E0349 no operator ">>" matches these operands test c:\Users\Medion\source\repos\test\test\Source.cpp 5
Error (active) E0065 expected a ';' test c:\Users\Medion\source\repos\test\test\Source.cpp 6
Severity Code Description Project File Line Suppression State
Error C2784 'std::basic_istream<_Elem,_Traits> &std::operator >>(std::basic_istream<_Elem,_Traits> &,_Elem *)': could not deduce template argument for 'std::basic_istream<_Elem,_Traits> &' from 'std::basic_ostream<char,std::char_traits<char>>' test c:\users\medion\source\repos\test\test\source.cpp 6
Error C2784 'std::basic_istream<_Elem,_Traits> &std::operator >>(std::basic_istream<_Elem,_Traits> &,_Elem &)': could not deduce template argument for 'std::basic_istream<_Elem,_Traits> &' from 'std::basic_ostream<char,std::char_traits<char>>' test c:\users\medion\source\repos\test\test\source.cpp 6
Error C2784 'std::basic_istream<char,_Traits> &std::operator >>(std::basic_istream<char,_Traits> &,signed char *)': could not deduce template argument for 'std::basic_istream<char,_Traits> &' from 'std::basic_ostream<char,std::char_traits<char>>' test c:\users\medion\source\repos\test\test\source.cpp 6
Error C2784 'std::basic_istream<char,_Traits> &std::operator >>(std::basic_istream<char,_Traits> &,signed char &)': could not deduce template argument for 'std::basic_istream<char,_Traits> &' from 'std::basic_ostream<char,std::char_traits<char>>' test c:\users\medion\source\repos\test\test\source.cpp 6
Error C2784 'std::basic_istream<char,_Traits> &std::operator >>(std::basic_istream<char,_Traits> &,unsigned char *)': could not deduce template argument for 'std::basic_istream<char,_Traits> &' from 'std::basic_ostream<char,std::char_traits<char>>' test c:\users\medion\source\repos\test\test\source.cpp 6
Error C2784 'std::basic_istream<char,_Traits> &std::operator >>(std::basic_istream<char,_Traits> &,unsigned char &)': could not deduce template argument for 'std::basic_istream<char,_Traits> &' from 'std::basic_ostream<char,std::char_traits<char>>' test c:\users\medion\source\repos\test\test\source.cpp 6
Error C2784 'std::basic_istream<_Elem,_Traits> &std::operator >>(std::basic_istream<_Elem,_Traits> &&,_Ty &&)': could not deduce template argument for 'std::basic_istream<_Elem,_Traits> &&' from 'std::basic_ostream<char,std::char_traits<char>>' test c:\users\medion\source\repos\test\test\source.cpp 6
Error C2676 binary '>>': 'std::basic_ostream<char,std::char_traits<char>>' does not define this operator or a conversion to a type acceptable to the predefined operator test c:\users\medion\source\repos\test\test\source.cpp 5
Error C2143 syntax error: missing ';' before 'return' test c:\users\medion\source\repos\test\test\source.cpp 6
What is wrong?
should be
The compiler was complaining that std::cout doesn't know what to do with the >> operator.
Alex did you get this info from any books or websites, or did you learn it yourself then type it out? This is very impressive. I am creating a Word document for all of these lessons. If you give me your email i can give it to you. But for now i want to focus on this question.
This information was found in the output error list. Specifically the 2nd and 3rd lines.
"Error (active) E0349 no operator ">>" matches these operands test c:\Users\Medion\source\repos\test\test\Source.cpp 5
Error (active) E0065 expected a ';' test c:\Users\Medion\source\repos\test\test\Source.cpp 6 "
These errors state that:
">>" is not an operator in cpp. This is because it is actually supposed to be "<<". The complier was confused with the ">>" command as it didn't know what to do with it. Then the compiler couldn't complete the compilation due to the missing ";", which indicates the end of a statement.
This is a basic syntax error
All other errors are caused by those 2 syntax errors.
I can help you on this error.
I am ready to code