What does control reaches end of non-void function mean

Question

I ve been getting strange compiler errors on this binary search algorithm  I get a warning that control reaches end of non-void function  What does this mean   int binary int val  int sorted    int low  int high        int mid    low high  2       if high  lt  low          return -1       if val  lt  sorted mid           return binary val  sorted  low  mid-1        else if val  gt  sorted mid           return binary val  sorted  mid 1  high        else if val    sorted mid           return mid

User · Answer

The compiler isn t smart enough to know that  lt    gt   and    are a  complete set   You can let it know that by removing the condition  if val    sorted mid    -- it s redundant  Jut say  else return mid

User · Answer

It means it s searching for a function that needs to be completed  else if val    sorted mid   return mid  so  remove the if   part and modify the code or add an else   at the end which returns an int

User · Answer

add to your code     include  lt  stdlib h gt    return EXIT SUCCESS    at the end of main

User · Answer

Make sure that your code is returning a value of given return-type irrespective of conditional statements This code snippet was showing the same error int search char arr    int start  int end  char value        int i      for i start  i lt  end  i                  if arr i     value              return i           This is the working code after little changes int search char arr    int start  int end  char value        int i      int index -1      for i start  i lt  end  i                  if arr i     value              index i            return index

User · Answer

Compiler by itself would not know that the conditions you have given are optimum    meaning of this is you have covered all cases    So therefore it always wants a return statement     So either you can change last else if with else or just write return 0 after last else if   int binary int val  int sorted    int low  int high    int mid    low high  2  if high  lt  low      return -1   if val  lt  sorted mid       return binary val  sorted  low  mid-1    else if val  gt  sorted mid       return binary val  sorted  mid 1  high    else if val    sorted mid       return mid  return 0

User · Answer

Always build with at least minimal optimization  With -O0  all analysis that the compiler could use to determine that execution cannot reach the end of the function has been disabled  This is why you re seeing the warning  The only time you should ever use -O0 is for step-by-line debugging  which is usually not a good debugging approach anyway  but it s what most people who got started with MSVC learned on

User · Answer

I had the same problem   My code below didn t work  but when I replaced the last  if  with  else   it works    The error was  may reach end of non-void function   int shifted char key letter              if isupper key letter                         return key letter -  A                       if islower key letter       lt ----------- doesn t work  replace with else                                                                      return key letter -  a

User · Answer

The compiler cannot tell from that code if the function will ever reach the end and still return something  To make that clear  replace the last else if      with just else

[c] What does "control reaches end of non-void function" mean?

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