how to pass char** as a const char*[] to a function?

Question

I have a char** variable and I want to pass it to a function that accepts const char*[]

int getList(const char* list[], int count){ return 0;}

int main(){
    int listsize = 4, charsize = 100, res = 0;
    char** li = nullptr;

    li = new char*[listsize];
    for (int i = 0; i<listsize; i++){
        li[i] = new char[charsize];
        strcpy(li[i],"Please Help ME!");
    }
    
    //This is where I get the compiler error because char** is not const char* list[]
    res = getList(li,listsize);

    for (int i = 0; i<listsize; i++) delete[] li[i];
    delete[] li;
}

I tried to cast it but couldn't get it to work.

typo: `getlist` vs `getList`. Note the capital `L`. Transcription error? — user4581301, Dec 09 '22 at 17:38
You have `std::vector>`, or if always 4 strings, `std::array` — BoP, Dec 09 '22 at 17:42
https://isocpp.org/wiki/faq/const-correctness#constptrptr-conversion — apple apple, Dec 09 '22 at 17:44
Does this answer your question? [Why am I getting an error converting a ‘float\*\*’ to ‘const float\*\*’?](https://stackoverflow.com/questions/2463473/why-am-i-getting-an-error-converting-a-float-to-const-float) — apple apple, Dec 09 '22 at 17:45
The best answer is to unask the question. Just don't to this. C-style arrays are hard to work with, and will give you endless headaches. — Pete Becker, Dec 09 '22 at 18:08

score 3 · Accepted Answer · answered Dec 09 '22 at 17:44

3

const can only be added to the "innermost" member of a set of multiple pointers, so a char ** cannot be automatically converted to a const char **. You'll need to add a const_cast:

res = getList(const_cast<const char **>(li),listsize);

answered Dec 09 '22 at 17:44

dbush

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how to pass char** as a const char*[] to a function?

1 Answers1

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