I am modifying the linux kernel for a device locally and I added a header file, say a.h inside /include/linux and referenced it in two C files inside the kernel directory. The header file contains a structure which has been initialised there itself. Whenever I compile the kernel, it shows me a multiple definition of 'struct_var' error. What changes should I make?

  • You need to ensure the initialisation only happens once (not in the header file). For a specific answer you’d need to edit your question to include the declarations in question. – Stephen Kitt Jun 7 '17 at 13:29

You need to ensure that it is only included once.

Typically, you would use


// your file contents go here


That way, the second time the compiler includes this file, UNIQUE_IDENTIFIER_MAYBE_THE_FILENAME is defined, so it does not define any of the bits inside.

  • Thanks, but I had already tried this and this hadn't worked! – Vishal Khopkar Jun 7 '17 at 17:40
  • That is strange. This method has been used for over 20 years to stop multiple definitions. We may need more information, or an example to help more. – Xetius Jun 14 '17 at 8:59
  • No issues, I found out a way; thanks for your help! – Vishal Khopkar Jul 14 '17 at 5:30

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