ImperialViolet

Turns out that char isn't short for signed char, it's a distinct type:

% cat tmp.c
void foo(void)
{
    signed char   *ps = "signed?";
    unsigned char *pu = "unsigned?";
}
% gcc -c tmp.c
tmp.c: In function 'foo':
tmp.c:3: warning: pointer targets in initialization differ in signedness
tmp.c:4: warning: pointer targets in initialization differ in signedness

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