can we give size of static array a variable

Question

hello every one i want to ask that i have read that we can declare dynamic array only by using pointer and using malloc or newlike

int * array = new int[strlen(argv[2])];

but i have wrote

int array[strlen(argv[2])];

it gave me no error

i have read that static array can only be declared by giving constant array size but here i have given a variable size to static array

why is it so thanks

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is it safe to use or is there chance that at any latter stages it will make problem i am using gcc linux

Answer 1

What you have is called a variable-length array (VLA), and it is not part of C++, although it is part of C99. Many compilers offer this feature as an extension.

Even the very new C++11 doesn't include VLAs, as the entire concept doesn't fit well into the advanced type system of C++11 (e.g. what is decltype(array)?), and C++ offers out-of-the box library solutions for runtime-sized arrays that are much more powerful (like std::vector).

In GCC, compiling with -std=c++98/c++03/c++0x and -pedantic will give you a warning.

Answer 2

C99 support variable length array, it defines at c99, section 6.7.5.2.

Answer 3

What you have written works in C99. It is a new addition named "variable length arrays". The use of these arrays is often discouraged because there is no interface through which the allocation can fail (malloc can return NULL, but if a VLA cannot be allocated, the program will segfault or worse, behave erratically).