Linker In Dev C++
Nov 29, 2016 Hansoft is the agile project management tool for enterprise teams. Fast, efficient, and flexible, Hansoft empowers teams to collaborate more efficiently so they can advance together and build better products. Hansoft runs natively on leading operating sytems including OS. Why can't I use conio.h functions like clrsrc? Because conio.h is not part of the C standard. It is a Borland extension, and works only with Borland compilers (and perhaps some other commercial compilers). Dev-C uses GCC, the GNU Compiler Collection, as it's compiler.GCC is originally a UNIX compiler, and aims for portability and standards-compliance. Jun 14, 2011 Try: 1) click on the Projects -'Project Options'-'Parameters' 2) under 'Linker', where it says: 'Add Library or Object', click that button, 3) scan across the list until you find the library you want to link, (.if libcurl.a is not in the default /lib/ folder, then select the correct folder), Double click on it, that will place libcurl.a in the linker list, repeat process for more libraries. Jul 20, 2009 I've got a bad feeling about this. With a library name like libwmp3.lib this library was not made to be compiled with g (or mingw) compiler. But I,ve been and looked at the source code download, and the package contains a file called.
Introduction
In this article I’ll be looking at the “undefined reference” error message (or “unresolved external symbol, for Visual C++ users). This is not actually a message from the compiler, but is emitted by the linker, so the first thing to do is to understand what the linker is, and what it does.
Apr 23, 2006 Here is what resolved this problem, as per part of the FAQ at Dev-C website: void WinMain 'changed to' int main allowed the compilation to complete and create main.o. Note: if you only change WinMain to main and keep the void, likely your compilation will continue to fail.
Sep 10, 2009 Hello, my name is Chandler Shen, a developer from the Visual C Shanghai team. We have made some changes in the upcoming Visual C 2010 release to improve the performance of linker. I would like to first give a brief overview of the linker. Dec 29, 2010 1. Update the compiler used by Dev C, this is probably not an appropriate approach for a beginner though it's not hard to do 2. Remove the installation of mingw and reinstall it elsewhere (e.g., c:mingw4.5), this is an easy fix but don't forget to update your path variable to reflect the new directory (c:mingw4.5MinGWbin).
Linker 101
To understand the linker, you have to understand how C++ programs are built. For all but the very simplest programs, the program is composed of multiple C++ source files (also known as “translation units”). These are compiled separately, using the C++ compiler, to produce object code files (files with a .o or a .obj extension) which contain machine code. Each object code file knows nothing about the others, so if you call a function from one object file that exists in another, the compiler cannot provide the address of the called function.
This is where the the linker comes in. Once all the object files have been produced, the linker looks at them and works out what the final addresses of functions in the executable will be. It then patches up the addresses the compiler could not provide. It does the same for any libraries (.a and .lib files) you may be using. And finally it writes the executable file out to disk.
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The linker is normally a separate program from the compiler (for example, the GCC linker is called ld) but will normally be called for you when you use your compiler suite’s driver program (so the GCC driver g++ will call ld for you).
Traditionally, linker technology has lagged behind compilers, mostly because it’s generally more fun to build a compiler than to build a linker. And linkers do not necessarily have access to the source code for the object files they are linking. Put together, you get a situation where linker errors, and the reasons for them, can be cryptic in the extreme.
Undefined reference
Put simply, the “undefined reference” error means you have a reference (nothing to do with the C++ reference type) to a name (function, variable, constant etc.) in your program that the linker cannot find a definition for when it looks through all the object files and libraries that make up your project. There are any number of reasons why it can’t find the definition – we’ll look at the commonest ones now.
No Definition
Probably the most common reason for unresolved reference errors is that you simply have not defined the thing you are referencing. This code illustrates the problem:
Here, we have a declaration of the function foo(), which we call in main(), but no definition. So we get the error (slightly edited for clarity):
The way to fix it is to provide the definition:
Wrong Definition
Another common error is to provide a definition that does not match up with declaration (or vice versa). For example, if the code above we had provided a definition of foo() that looked like this:
then we would still get an error from the linker because the signatures (name, plus parameter list types) of the declaration and definition don’t match, so the definition actually defines a completely different function from the one in the declaration. To avoid this problem, take some care when writing declarations and definitions, and remember that things like references, pointers and const all count towards making a function signature unique.
Didn’t Link Object File
This is another common problem. Suppose you have two C++ source files:
and:
If you compile f1.cpp on its own you get this:
and if you compile f2.cpp on its own, you get this even more frightening one:
In this situation, you need to compile both the the source files on the same command line, for example, using GCC:
or if you have compiled them separately down to object files:
For further information on compiling and linking multiple files in C++, particularly with GCC, please see my series of three blog articles starting here.
Wrong Project Type
The linker error regarding WinMain above can occur in a number of situations, particularly when you are using a C++ IDE such as CodeBlocks or Visual Studio. These IDEs offer you a number of project types such as “Windows Application” and “Console Application”. If you want to write a program that has a int main() function in it, always make sure that you choose “Console Application”, otherwise the IDE may configure the linker to expect to find a WinMain() function instead.
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No Library
To understand this issue, remember that a header file (.h) is not a library. The linker neither knows nor cares about header files – it cares about .a and .lib files. So if you get a linker error regarding a name that is in a library you are using, it is almost certainly because you have not linked with that library. To perform the linkage, if you are using an IDE you can normally simply add the library to your project, if using the command line, once again please see my series of blog articles on the GCC command line starting here, which describes some other linker issues you may have.
Conclusion
The unresolved reference error can have many causes, far from all of which have been described here. But it’s not magic – like all errors it means that you have done something wrong, in you code and/or your project’s configuration, and you need to take some time to sit down, think logically, and figure out what.
What Is A Linker
C/C++ support for Visual Studio Code is provided by a Microsoft C/C++ extension to enable cross-platform C and C++ development on Windows, Linux, and macOS.
Getting started
C/C++ compiler and debugger
The C/C++ extension does not include a C++ compiler or debugger. You will need to install these tools or use those already installed on your computer.
Popular C++ compilers are:
How Linkers Work
- GCC on Linux
- GCC via Mingw-w64 on Windows
- Microsoft C++ compiler on Windows
- Clang for XCode on macOS
Make sure your compiler executable is in your platform path so the extension can find it. You can check availability of your C++ tools by opening the Integrated Terminal (⌃` (Windows, Linux Ctrl+`)) in VS Code and try running the executable (for example g++ --help).
Install the Microsoft C/C++ extension
- Open VS Code.
- Click the Extensions view icon on the Sidebar (⇧⌘X (Windows, Linux Ctrl+Shift+X)).
- Search for
c++. - Click Install.
C++ Linker Error
Hello World tutorials
Get started with C++ and VS Code with Hello World tutorials for your environment:
Documentation
Linker Program
You can find more documentation on using the Microsoft C/C++ extension under the C++ section, where you'll find topics on:
Remote Development
VS Code and the C++ extension support Remote Development allowing you to work over SSH on a remote machine or VM, inside a Docker container, or in the Windows Subsystem for Linux (WSL).
To install support for Remote Development:
- Install the VS Code Remote Development Extension Pack.
- If the remote source files are hosted in WSL, use the Remote - WSL extension.
- If you are connecting to a remote machine with SSH, use the Remote - SSH extension.
- If the remote source files are hosted in a container (for example, Docker), use the Remote - Containers extension.
Feedback
If you run into any issues or have suggestions for the Microsoft C/C++ extension, please file issues and suggestions on GitHub. If you haven't already provided feedback, please take this quick survey to help shape this extension for your needs.