Expression evaluation inside the while loop

Question

How many times CppBuzz.com is printed?

   int main()
    {
      int a = 0;
      while(a++ < 5-++a)
      printf("CppBuzz.com");
      return 0;
     }

how to solve the expression (5-++a) ?

score 1 · Answer 1 · answered Dec 10 '19 at 07:48

1

There is a bigger problem than determining loop counter in your code - undefined behavior.

The line

  while(a++ < 5-++a)

tries to increment the same variable a more than once without a sequence point, it invokes undefined behavior.

That said, if you don't want any conversion specification to happen, don't use printf(), use puts() instead.

answered Dec 10 '19 at 07:48

Sourav Ghosh

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With the GCC compiler, the statement gets printed even if a has undefined behavior. How is this possible? – rpj Dec 10 '19 at 09:00
@PadmaR Please note that [undefined](https://en.cppreference.com/w/cpp/language/ub) doesn't necessarily mean "it won't work". – Bob__ Dec 10 '19 at 09:06

score 1 · Answer 2 · answered Dec 10 '19 at 07:48

Code invoked undefined behaviour. Here multiple time variable a increments.

GCC Compiler generates warning:

prog.c: In function 'main':
prog.c:8:21: warning: operation on 'a' may be undefined [-Wsequence-point]
       while(a++ < 5-++a)
                     ^~~

Expression evaluation inside the while loop

2 Answers2