when array initialized as [0] size.Still able to assign value

Asked May 11 '20 at 04:55

Active May 11 '20 at 05:01

Viewed 47 times

Initially, array declared with zero. Still, the compiler is not throwing error.

int x_var[0];
cout<<"Hello World"<<x_var[0]<<endl; // <<<<<<<<<<<< prints random number

x_var[0]=1;                          // >>>>> compiler is not throwing error.
                                     // But initialized array as zero.It must throw error
cout<<"Hello World"<<x_var[0]<<endl; // <<<<<<<<<<<<Prints value 1

edited May 11 '20 at 05:01

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asked May 11 '20 at 04:55

Manju

Index out of bounds is undefined behaviour in C++, not a compilation error or a runtime exception. – user207421 May 11 '20 at 05:00
Arrays of size 0 are illegal in C++. The compiler should issue an error on the declaration `int x_var[0];`. – dxiv May 11 '20 at 05:02
OT: "But initialized array as zero" well, no. You set the array size to zero – Support Ukraine May 11 '20 at 05:02
@dxiv The compiler should *print* an error. Exceptions are thrown. Compilation errors are printed. – user207421 May 11 '20 at 05:02
@dxiv GCC [doesn't](https://godbolt.org/z/bMCURQ) apparently, possibly because of the VLA extension. – eesiraed May 11 '20 at 05:04
For GCC use: `g++ -Wall -Wextra -pedantic main.cpp` and you'll get a warning – Support Ukraine May 11 '20 at 05:04
@user207421 That was "throw" in English language, not C++ language ;-) – dxiv May 11 '20 at 05:04
@dxiv It was a misleading use of a term of art in C++. Don't misuse standard terminology. – user207421 May 11 '20 at 05:05
@4386427 See [here](https://stackoverflow.com/a/6180200) for example. – dxiv May 11 '20 at 05:07
Also see https://stackoverflow.com/a/36577430/4386427 – Support Ukraine May 11 '20 at 05:16
Man, some compilers just have no Standards. – user4581301 May 11 '20 at 05:17
1

*the compiler should give a diagnostic if invoked in standard mode – M.M May 11 '20 at 05:41

when array initialized as [0] size.Still able to assign value

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