Omitting return statement in C++

by

Omitting the return statement in a non-void function [Except main()] and using the returned value in your code invokes Undefined Behaviour.

ISO C++-98[Section 6.6.3/2]

A return statement with an expression can be used
only in functions returning a value; the value of the expression is
returned to the caller of the function. If required, the expression
is implicitly converted to the return type of the function in which it
appears. A return statement can involve the construction and copy of
a temporary object (class.temporary). Flowing off the end of a
function is equivalent to a return with no value; this results in
undefined behavior in a value-returning function.

For example

int func()
{
    int a=10;
    //do something with 'a'
    //oops no return statement
}


int main()
{
     int p=func();
     //using p is dangerous now
     //return statement is optional here 
}

Generally g++ gives a warning: control reaches end of non-void function. Try compiling with -Wall option.

More Related Contents:

  1. Why does flowing off the end of a non-void function without returning a value not produce a compiler error?
  2. to_string is not a member of std, says g++ (mingw)
  3. C++11 make_pair with specified template parameters doesn’t compile
  4. Tail recursion in C++
  5. VSCode c++ task.json include path and libraries
  6. Getting mangled name from demangled name
  7. Why do I need to use typedef typename in g++ but not VS?
  8. g++ “calling” a function without parenthesis (not f() but f; ). Why does it always return 1?
  9. gcc/g++: “No such file or directory”
  10. error: expected class-name before ‘{’ token
  11. Standard-layout and tail padding
  12. Update GCC on OSX
  13. error: use of deleted function
  14. A class name introduced inside a class is not treated as a nested class name
  15. GNU C++ how to check when -std=c++0x is in effect?
  16. g++ How to get warning on ignoring function return value
  17. SetJmp/LongJmp: Why is this throwing a segfault?
  18. How to use profile guided optimizations in g++?
  19. How to compile C++ with C++11 support in Mac Terminal
  20. How to produce deterministic binary output with g++?
  21. Does the restrict keyword provide significant benefits in gcc/g++?
  22. Convert a Static Library to a Shared Library (create libsome.so from libsome.a): where’s my symbols?
  23. What is a .h.gch file?
  24. Do I really have to worry about alignment when using placement new operator?
  25. Why can’t I use with g++ 4.9.2?
  26. Understanding -Weffc++
  27. Why does stack not compile in g++? [duplicate]
  28. Eclipse C++ : “Program “g++” not found in PATH”
  29. get part of std::tuple
  30. std::array with aggregate initialization on g++ generates huge code

Leave a Comment