Why Am I Getting 'Undefined Reference to 'vtable for XXX'' or 'ClassName::ClassName()' Linker Errors in My C Project?

GCC C Linker Error: Undefined Reference to 'vtable for XXX', 'ClassName::ClassName()'

While linking a C project in Eclipse-CDT, users may encounter linker errors like "undefined reference to 'vtable for XXX'" or "undefined reference to 'ClassName::ClassName()'". These errors point to underlying issues that prevent successful library linking.

1. Confirming Static Library Type

To verify the 64-bit nature of static libraries, run the following command in the terminal:

file /path/to/library.a | grep -i "64-bit"

If "64-bit" is present in the output, the library is 64-bit.

2. Library Class and Method Validation

To check if the library contains the expected class and methods, use a C header viewer tool like ctags or lldb. For example, using ctags in the terminal:

ctags -R /path/to/library_header_files_directory
find /path/to/tags_file_directory NameOfClass

This command searches for the class name in the tags file generated from the header files and indicates whether it exists in the library.

3. Understanding the Error

In this case, the linker errors indicate a missing definition for overridden virtual functions in the "SomeOtherClass" class. The declaration exists but lacks an implementation. To resolve this issue, provide a definition for the missing method in "SomeOtherClass".

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