What causes the error undefined reference to some function

Question

I get the error   main o  text 0x1ed   In function  main     undefined reference to  avergecolumns  collect2  ld returned 1 exit status   when I gcc   o   I m not quite sure what causes this error   Other posters have explained it as the function is not found or the function is empty   If someone could clarify or refine  it would be greaty appreciated   Here is my function s code I m trying to calculate the average of the column in 2D arrays     include  my h   void averagecolumns  int x  int y  int   a        int i      int j      float sum      float colAvg       sum   0      colAvg   0       printf  i   The column averages are   n        for i   0  i  lt  x  i                          for j   0  j  lt  y  j                                          sum    a i  j                       colAvg   sum    float x                                printf  Column   3d  Average   6 2f   j  colAvg               sum   0                 colAvg   0              The relavent parts of main are    include  my h   int main  int argc  char  argv           int   a       float   colAvg       int ROWS       int COLS       int i       int j       int   table       FILE  fpmyfile       int closeResult                      printme  ROWS  COLS  a                                   call functions a - j              oddvalues  ROWS  COLS  a                oddlocations  ROWS  COLS  a                countoddrows  ROWS  COLS  a                addrows  ROWS  COLS  a                findfirstsmall  ROWS  COLS  a                findlastlarge  ROWS COLS  a                                          addcolumns  ROWS  COLS  a                avergecolumns  ROWS  COLS  a              Also  is this a linker or a compile error  I wasn t sure which tag to add

User · Accepted Answer

It s a linker error  ld is the linker  so if you get an error message ending with  ld returned 1 exit status   that tells you that it s a linker error   The error message tells you that none of the object files you re linking against contains a definition for avergecolumns  The reason for that is that the function you ve defined is called averagecolumns  in other words  you misspelled the function name when calling the function  and presumably in the header file as well - otherwise you d have gotten a different error at compile time

[c] What causes the error "undefined reference to (some function)"?

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