source: doc/theses/mike_brooks_MMath/programs/bkgd-carray-decay.c @ 4c8f29ff

#include <assert.h>
int main() {
        float ar[10];                           $\C{// array}$
        float (*pa)[10] = &ar;          $\C{// pointer to array}$
        float a0 = ar[0];                       $\C{// element}$
        float * pa0 = &(ar[0]);         $\C{// pointer to element}$

        float * pa0x = ar;                      $\C{// (ok)}$
        assert( pa0 == pa0x );
        assert( sizeof(pa0x) != sizeof(ar) );

        void f( float x[10], float * y ) {
                static_assert( sizeof(x) == sizeof(void *) );
                static_assert( sizeof(y) == sizeof(void *) );
        }
        f( 0, 0 );

        // reusing local var `float a[10];`}
        float v;
        f( ar, ar );                            $\C{// ok: two decays, one into an array spelling}$
        f( &v, &v );                            $\C{// ok: no decays; a non-array passes to an array spelling}$

        char ca[] = "hello";            $\C{// array on stack, initialized from read-only data}$
        char * cp = "hello";            $\C{// pointer to read-only data [decay here]}$
        void edit( char c[] ) {         $\C{// parameter is pointer}$
                c[3] = 'p';
        }
        edit( ca );                                     $\C{// ok [decay here]}$
        edit( cp );                                     $\C{// Segmentation fault}$
        edit( "hello" );                        $\C{// Segmentation fault [decay here]}$

        void decay( float x[10] ) {
                static_assert( sizeof(x) == sizeof(void *) );
        }
        static_assert( sizeof(ar) == 10 * sizeof(float) );
        decay( ar );

        void no_decay( float (*px)[10] ) {
                static_assert( sizeof(*px) == 10 * sizeof(float) );
        }
        static_assert( sizeof(*pa) == 10 * sizeof(float) );
        no_decay( pa );
}

// Local Variables: //
// compile-command: "sed -f sedcmd bkgd-carray-decay.c | gcc-11 -Wall -Wextra -x c -" //
// End: //