c - Why is scanf("%hhu", char*) overwriting other variables when they are local? -

the title says all. i'm using gcc 4.7.1 (bundled codeblocks) , faced strange issue. consider this:

int main() {     unsigned char = 0, b = 0, c = 0;     scanf("%hhu", &a);     printf("a = %hhu, b = %hhu, c = %hhu\n", a, b, c);     scanf("%hhu", &b);     printf("a = %hhu, b = %hhu, c = %hhu\n", a, b, c);     scanf("%hhu", &c);     printf("a = %hhu, b = %hhu, c = %hhu\n", a, b, c);     return 0; } 

for inputs 1, 2 , 3, outputs

a = 1, b = 0, c = 0 = 0, b = 2, c = 0 = 0, b = 0, c = 3 

if i, however, declare a, b , c global variables, works expected. why happenning?

thank in advance

other details:

i'm running windows 8 64 bits. tried -std=c99 , problem persists.

further research

testing code

void printarray(unsigned char *a, int n) {     while(n--)         printf("%hhu ", *(a++));     printf("\n"); }  int main() {     unsigned char array[8];     memset(array, 255, 8);     printarray(array, 8);     scanf("%hhu", array);     printarray(array, 8);     return 0; } 

shows scanf interpreting "%hhu" "%u". directly ignoring "hh". output of code input 1 is:

255 255 255 255 255 255 255 255 1 0 0 0 255 255 255 255 

the important detail you're using windows, , presumably outdated or non-conforming c environment (compiler , standard library). msvcrt supports c89 (and then, not entirely correctly); in particular, there no "hh" modifier in c89, , it's interpreting "hh" same "h" (i.e. short).