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gcc Warning: Array index has type 'char'

While trying to compile a programme, i get the following warning:

tokenizer.cpp:121: warning: array subscript has type 'char'

The array is a table mapping special meanings to the ASCII character sets. For instance i want to extract quotes, whitespace and such:

Code:

#include <stdio.h>

#include <string.h>



const char tokTable[128];



void parseInput(const char* input) {

    int posCount=0;

    while (*input) {

        if (tokTable[*input]==1){

            printf("found a space at pos: %d\n",posCount);

        }

        ++input; ++posCount;

    }

}



int main(int argc, const char** argv) {

    char* ptok=(char*)tokTable;

    bzero(ptok,sizeof(tokTable));

    ptok[32]=1; // space

    //tokTable[]; and so forth

    parseInput("Hey you!");

    return 0;

}

How can i fix the warning at: 'tokTable[*input]'

I am using gcc 4.3.0

Cast it to int. But I can't see why it's giving a warning for a lossless conversion.

That did the trick.

Thank you.

Quote:

Originally Posted by Dan04 (Post 3127119)

But I can't see why it's giving a warning for a lossless conversion.

The warning is enabled by “-Wchar-subscripts” or its superset “-Wall” as a command-line option. It is only a warning (not an error), and your usage is valid C++. The reason there is a warning for this is that the type char may be signed, in which case a high-bit value might be a negative index in your subscript (which may or may not be what you want, but is a common source of bugs).

That makes sense. I've been bitten by signed chars a few times.