Why does this seemingly simple implementation of "strupr" not work?

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Error implementation in GCC:

    char* strupr( char *str )
    {
    while(*str) {
        *str++ = toupper(*str);
        }
    }

Note that str is used twice in the assignment.

c string pointer

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1 answer

3

There are 2 problems: adding the pointer there will generate an undefined behavior and is not returning anything, have to change the function signature or return something. That’s how it works:

#include <stdio.h>
#include <ctype.h>

void strupr(char *str) {
    while (*str) {
        *str = toupper(*str);
        str++;
    }
}
    
int main(void) {
    char texto[] = "teste";
    strupr(texto);
    printf("%s", texto);
    return 0;
}

Behold working in the ideone. And in the repl it.. Also put on the Github for future reference.

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