1.25.verification - Reasoning About Code int deref(int*p...

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Reasoning About Code 1/25/2010
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int deref(int *p) { return *p; }
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/* requires: p != NULL */ int deref(int *p) { return *p; }
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int sum(int a[], size_t n) { int total = 0; for (size_t i=0; i<n; i++) total += a[i]; return total; }
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/* requires: a != NULL && size(a) >= n */ int sum(int a[], size_t n) { int total = 0; for (size_t i=0; i<n; i++) total += a[i]; return total; }
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/* requires: a != NULL && size(a) >= n */ int sum(int a[], size_t n) { int total = 0; for (size_t i=0; i<n; i++) total += a[i]; return total; }
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/* requires: a != NULL && size(a) >= n */ int sum(int a[], size_t n) { int total = 0; for (size_t i=0; i<n; i++) /* 0 <= i && i < n && n <= size(a) */ total += a[i]; return total; }
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int sumderef(int *a[], size_t n) { int total = 0, i; for (i=0; i<n; i++) total += *(a[i]); return total; }
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int sumderef(int *a[], size_t n) { int total = 0, i; for (i=0; i<n; i++) total += *(a[i]); return total; } Woops! If (int)n < 0, i becomes negative, and a[i] is unsafe.
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int sumderef(int *a[], size_t n) { int total = 0; for (size_t i=0; i<n; i++) total += *(a[i]); return total; }
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/* requires: a != NULL && size(a) >= n && ??? */ int sumderef(int *a[], size_t n) { int total = 0; for (size_t i=0; i<n; i++) total += *(a[i]); return total; }
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/* requires: a != NULL && size(a) >= n && for all j in 0..n-1, a[j] != NULL */ int sumderef(int *a[], size_t n) { int total = 0; for (size_t i=0; i<n; i++) total += *(a[i]); return total; }
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void *mymalloc(size_t n) { void *p = malloc(n); if (!p) { perror("malloc"); exit(1); } return p; }
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/* ensures: retval != NULL */ void *mymalloc(size_t n) { void *p = malloc(n); if (!p) { perror("malloc"); exit(1); } return p; }
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