incompatible conversion error in C

Question

Compiler is complaining about incompatible variable types stored in array. This happens, when I'm trying to convert characters from argv[1] to uppercase (first for loop). Similar error occurs in second for loop, where I'd like to convert chars to their ASCII equivalent and subtract 64 from it. What do?

//converts chars in argv[1] to uppercase letters
for (int i = 0, n = strlen(argv[1]); i < n; i++){
    argv[i] = toupper(argv[i]);
    }

//converts chars in argv[1] to numbers 
int key[strlen(argv[1])];
for (int i = 0, n = strlen(argv[1]); i<n; i++){
    key[i]= argv[i]-64;

Error mesagges:

incompatible integer to pointer conversion assigning to 'string' (aka 'char *') from 'int' [-Werror,-Wint-conversion]

and

incompatible pointer to integer conversion assigning to 'int' from 'string' (aka 'char *') [-Werror,-Wint-conversion]

`toupper()` converts a single `char`, not a string. Suggest `argv[1][i] = toupper((unsigned char) argv[1][i]);` — chux - Reinstate Monica, Jan 12 '17 at 17:05
Possible duplicate of [toupper function](http://stackoverflow.com/questions/15057899/toupper-function) — Ruud Helderman, Jan 12 '17 at 17:07
Take ` n = strlen(argv[1])` out of the loop initialization and put it in the main code. Then it does not have to be repeated in the second loop initialization. — sabbahillel, Jan 12 '17 at 17:31
@jurhas: You mean "dereferenced"? And the `argv` argument of `main` is not `void *` (nor `void **`) — too honest for this site, Jan 12 '17 at 17:43

score 0 · Accepted Answer · answered Jan 12 '17 at 17:08

It seems you mean

for (int i = 0, n = strlen(argv[1]); i < n; i++){
    argv[1][i] = toupper( ( unsigned char )argv[1][i]);
    }

//converts chars in argv[1] to numbers 
int key[strlen(argv[1])];
for (int i = 0, n = strlen(argv[1]); i<n; i++){
    key[i]= argv[1][i]-64;

incompatible conversion error in C

1 Answers1