Multiple definition of linker error

Question

I defined a special file  config h  My project also has files   t c  t h pp c  pp h b c b h l cpp   and  includes   in t c        include  t h       include  b h       include  pp h       include  config h    in b c         include  b h       include  pp h    in pp c        include  pp h       include  config h    in l cpp        include  pp h       include  t h       include  config h    there are no include directives in my   h files  only in   c files  I defined this in config h   const char  names i                           brian    stefan    steve               and need that array in l cpp  t c  pp c but Im getting this error   pp o   data 0x0   multiple definition of  names  l o   data 0x0   first defined here t o   data 0x0   multiple definition of  names  l o   data 0x0   first defined here collect2  ld returned 1 exit status make       link  Error 1   I have include guards in every   h file I use in my project  Any help solving this

User · Accepted Answer

Don t define variables in headers  Put declarations in header and definitions in one of the  c files   In config h  extern const char  names      In some  c file   const char  names                    brian    stefan    steve           If you put a definition of a global variable in a header file  then this definition will go to every  c file that includes this header  and you will get multiple definition error because a varible may be declared multiple times but can be defined only once

User · Answer

Declarations of public functions go in header files  yes  but definitions are absolutely valid in headers as well  You may declare the definition as static  only 1 copy allowed for the entire program  if you are defining things in a header for utility functions that you don t want to have to define again in each c file  I E  defining an enum and a static function to translate the enum to a string  Then you won t have to rewrite the enum to string translator for each  c file that includes the header

[c] Multiple definition of ... linker error

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