Overview
In Eclipse, the Error: Symbol 'std' could not be resolved may be displayed when writing C++ code. This error occurs when compiler settings are incorrect and Eclipse could not find the standard C/C++ library. This documentation provides helpful advice and step-by-step instructions for resolving this error.
Symptoms
When this error is displayed, the source code may be highlighted in yellow with a small error indicator icon in the left margin. Hovering over the icon reveals the error message Symbol 'std' could not be resolved. Additionally, any reference to a standard library object, such as cin, cout, etc., may also be highlighted in yellow and display the same error message.
Causes
This error occurs when the C/C++ library configuration for the project is incorrect.
Solution
Step 1.
Right-click on the project, and select Properties from the list of options.
Step 2.
Navigate to C/C++ Build > Settings > Tool Settings on the Project Properties window.
Step 3.
Under GCC C++ Compiler > Includes, click Add....
Step 4.
Add the include path of the standard C or C++ library, depending on the type of code you are working with.
The recommended include path for the GNU C++ Library is /usr/include/c++/9.3.0.
Step 5.
Select Apply and Close and then Build Project the project. This should result in the error being resolved and the highlights removed from the code.
FAQ
Q: What's causing this error?
A: This error occurs due to incorrect compiler settings, specifically the lack of the standard C/C++ library path.
Q: How do I know if I'm using C or C++?
A: The distinction between C and C++ is based on the file extensions used. A file with the .cpp extension indicates that the code is using the C++ compiler. A .c extension indicates that the code is using the C compiler.
Q: What if I don't want to include the C/C++ library?
A: The C/C++ library should be included, as it contains a number of functions and objects that are used in the code. Without it, the symbols cannot be properly resolved.
Further Reading
Eclipse Wiki: Symbol 'std' could not be resolved
Stack Overflow Question: 'std' could not be resolved in Eclipse