Array size in CINT

ROOT
1

Hi Rooters,

One thing that always bother me about CINT is that it does not alllow to define an array size by a variable, like

int a = 10;
int array[a];

Is there other way to define array size by variable without compiling the code, i.e. in root script?

Thanks.

2

[quote=“manoj”]Hi Rooters,

One thing that always bother me about CINT is that it does not alllow to define an array size by a variable, like

int a = 10;
int array[a];

Is there other way to define array size by variable without compiling the code, i.e. in root script?

Thanks.[/quote]

Yes, use for example std::vector. In C++ the array size must be a constant expression. And your question is quite strange, since CINT DOES ALLOW to declare an array of variable length (I’m not sure if it’s an extension or a part of its C-language support, since C has VLAs). If you try to compile this with compiler, you’ll have a compilation error or at least a warning, depending on compiler, since your ‘a’ is not a constant expression.

And in general, VLAs are not recommended (I guess because of way compiler vendors usually implement them), for example, have a look here:

securecoding.cert.org/confl … llocations

While this is probably is not your case and not how CINT implements VLAs, still good to know.

3

The same as tpochep. It is not allowed in C. You have to write

const int a=10; int array[a];

4

[quote=“pamputt”]The same as tpochep. It is not allowed in C. You have to write

const int a=10; int array[a];[/quote]

It’s allowed in modern C (with some differences and limitations), but not C++ :wink:

P.S. Hmm, none of my compilers issues any diagnostic if an array size is a non-constant (g++ 4.8.1, clang 3.4), I have a warning only when compiling with ‘-pedantic’.