Command line arguments

[proud silo]

I dont understand why the const* is written twice.
Also, compiler says, second argument of main should be char** why is that?
I've used char* argv[] but I dont understand this one

#include <iostream>
int main (int const argc, char const*const* argv) {
  for (int i = 0; i < argc; ++i) {
    std::cout << argv[i] << '\n';
  }
}

[oak warren]

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[errant stag]

So first point, as a function argument char** argv and char* argv[] are equivalent

Second

!cdecl char const * const * argv

Damn, that command doesn't work :(

Basically it's saying that neither argv[n] or argv[n][m] can be changed

[hasty warren]

char const * const * means “pointer to const pointer to const char”

const char * const * is also the same

[proud silo]

🧐 “pointer to const pointer to const char”
looks a bit confusing

[hasty warren]

You read it from right to left

I know, it’s dumb

[rain beacon]

if you try to use char** argv and then try to redirect argv[1] to something or even worse, edit the chars of argv[1], you will have a bad time

[queen current]

@proud silochar* argv[] = char** argv those are the same

[rain beacon]

^ not completely

[queen current]

nvm all the expert have already answer you

[queen current]

let me know what u know about the different because i always write it like that char **argv

[rain beacon]

wait nvm, due to array decaying to pointer they are literally the same

[errant stag]

As I understand it, they are the same for function arguments, and initializing from aleady existing arrays
But as a local array, they are different

const char* argv[] = {"Hello", "world"}; // Valid
const char* argv2[] = argv; // Invalid
const char** argv3 = argv; // Valid

[rain beacon]

saying argv = NULL is the invalid part, you can't assign arrays

but you can assign to double pointers

[errant stag]

My point being is that the types are different.
It's just that for function arguments, C just decides to treat them the same

[proud silo]

Okay now I kinda get it.
Thanks for the help guys 👍

!solved

[oak warren]

Thank you and let us know if you have any more questions!

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[proud silo]

so . . .
something like

char const *str1 = "abc";

char const *const str2 = str1; // const pointer to const char *str1

char const *const *str3 = &str2; // pointer to const pointer of char type str2

and just to make it simple

char ch1 = 'a';

char *ch2 = &ch1;

char **const ch3 = &ch2;
  
char **const *ch4 = &ch3;

is that correct ?

[hasty warren]

Yup, but there is a * in one of the comments which i assume is a typo?

https://eisenwave.github.io/cdecl-plus/

This is a nice tool to clarify types

Made by @pseudo mauve