clang/test/Analysis/pointer-sub.c

   1 // RUN: %clang_analyze_cc1 -analyzer-checker=security.PointerSub -analyzer-output=text-minimal -verify %s
   2
   3 typedef int * Ptr;
   4
   5 void f1(void) {
   6   int x, y, z[10];
   7   int d = &y - &x; // expected-warning{{Subtraction of two pointers that do not point into the same array is undefined behavior}}
   8   d = z - &y; // expected-warning{{Subtraction of two pointers that do not point into the same array is undefined behavior}}
   9   d = &x - &x; // no-warning (subtraction of any two identical pointers is allowed)
  10   d = (long *)&x - (long *)&x;
  11   d = (&x + 1) - &x; // no-warning ('&x' is like a single-element array)
  12   d = &x - (&x + 1); // no-warning
  13   d = (&x + 0) - &x; // no-warning
  14   d = (z + 10) - z; // no-warning
  15   d = (long long)&y - (long long)&x; // no-warning
  16   long long l = 1;
  17   d = l - (long long)&y; // no-warning
  18   Ptr p1 = &x;
  19   Ptr p2 = &y;
  20   d = p1 - p2; // expected-warning{{Subtraction of two pointers that do not point into the same array is undefined behavior}}
  21 }
  22
  23 void f2(void) {
  24   int a[10], b[10], c; // expected-note{{Array at the left-hand side of subtraction}} \
  25                        // expected-note2{{Array at the right-hand side of subtraction}}
  26   int *p = &a[2];
  27   int *q = &a[8];
  28   int d = q - p; // no-warning (pointers into the same array)
  29
  30   q = &b[3];
  31   d = q - p; // expected-warning{{Subtraction of two pointers that}}
  32
  33   d = &a[4] - a; // no-warning
  34   d = &a[2] - p; // no-warning
  35   d = &c - p; // expected-warning{{Subtraction of two pointers that}}
  36
  37   d = (int *)((char *)(&a[4]) + sizeof(int)) - &a[4]; // no-warning (pointers into the same array data)
  38   d = (int *)((char *)(&a[4]) + 1) - &a[4]; // expected-warning{{Subtraction of two pointers that}}
  39
  40   long long a1 = (long long)&a[1];
  41   long long b1 = (long long)&b[1];
  42   d = a1 - b1;
  43 }
  44
  45 void f3(void) {
  46   int a[3][4]; // expected-note{{Array at the left-hand side of subtraction}} \
  47                // expected-note2{{Array at the right-hand side of subtraction}}
  48   int d;
  49
  50   d = &(a[2]) - &(a[1]);
  51   d = a[2] - a[1]; // expected-warning{{Subtraction of two pointers that}}
  52   d = a[1] - a[1];
  53   d = &(a[1][2]) - &(a[1][0]);
  54   d = &(a[1][2]) - &(a[0][0]); // expected-warning{{Subtraction of two pointers that}}
  55
  56   d = (int *)((char *)(&a[2][2]) + sizeof(int)) - &a[2][2]; // expected-warning{{Subtraction of two pointers that}}
  57   d = (int *)((char *)(&a[2][2]) + 1) - &a[2][2]; // expected-warning{{Subtraction of two pointers that}}
  58   d = (int (*)[4])((char *)&a[2] + sizeof(int (*)[4])) - &a[2]; // expected-warning{{Subtraction of two pointers that}}
  59   d = (int (*)[4])((char *)&a[2] + 1) - &a[2]; // expected-warning{{Subtraction of two pointers that}}
  60 }
  61
  62 void f4(void) {
  63   int n = 4, m = 3;
  64   int a[n][m];
  65   int (*p)[m] = a; // p == &a[0]
  66   p += 1; // p == &a[1]
  67
  68   // FIXME: This is a known problem with -Wpointer-arith (https://github.com/llvm/llvm-project/issues/28328)
  69   int d = p - a; // d == 1 // expected-warning{{subtraction of pointers to type 'int[m]' of zero size has undefined behavior}}
  70
  71   // FIXME: This is a known problem with -Wpointer-arith (https://github.com/llvm/llvm-project/issues/28328)
  72   d = &(a[2]) - &(a[1]); // expected-warning{{subtraction of pointers to type 'int[m]' of zero size has undefined behavior}}
  73
  74   d = a[2] - a[1]; // expected-warning{{Subtraction of two pointers that}}
  75 }
  76
  77 struct S {
  78   int a;
  79   int b;
  80   int c[10]; // expected-note2{{Array at the right-hand side of subtraction}}
  81   int d[10]; // expected-note2{{Array at the left-hand side of subtraction}}
  82 };
  83
  84 void f5(void) {
  85   struct S s;
  86   int y;
  87   int d;
  88
  89   d = &s.b - &s.a; // expected-warning{{Subtraction of two pointers that}}
  90   d = &s.c[0] - &s.a; // expected-warning{{Subtraction of two pointers that}}
  91   d = &s.b - &y; // expected-warning{{Subtraction of two pointers that}}
  92   d = &s.c[3] - &s.c[2];
  93   d = &s.d[3] - &s.c[2]; // expected-warning{{Subtraction of two pointers that}}
  94   d = s.d - s.c; // expected-warning{{Subtraction of two pointers that}}
  95
  96   struct S sa[10];
  97   d = &sa[2] - &sa[1];
  98   d = &sa[2].a - &sa[1].b; // expected-warning{{Subtraction of two pointers that}}
  99 }
 100
 101 void f6(void) {
 102   long long l = 2;
 103   char *a1 = (char *)&l;
 104   int d = a1[3] - l;
 105
 106   long long la1[3] = {1}; // expected-note{{Array at the right-hand side of subtraction}}
 107   long long la2[3] = {1}; // expected-note{{Array at the left-hand side of subtraction}}
 108   char *pla1 = (char *)la1;
 109   char *pla2 = (char *)la2;
 110   d = pla1[1] - pla1[0];
 111   d = (long long *)&pla1[1] - &l; // expected-warning{{Subtraction of two pointers that}}
 112   d = &pla2[3] - &pla1[3]; // expected-warning{{Subtraction of two pointers that}}
 113 }
 114
 115 void f7(int *p) {
 116   int a[10];
 117   int d = &a[10] - p; // no-warning ('p' is unknown, even if it cannot point into 'a')
 118 }
 119
 120 void f8(int n) {
 121   int a[10] = {1};
 122   int d = a[n] - a[0]; // no-warning
 123 }
 124
 125 int f9(const char *p1) {
 126   const char *p2 = p1;
 127   --p1;
 128   ++p2;
 129   return p1 - p2; // no-warning
 130 }
 131
 132 int f10(struct S *p1, struct S *p2) {
 133   return &p1->c[5] - &p2->c[5]; // no-warning
 134 }
 135
 136 struct S1 {
 137   int a;
 138   int b; // expected-note{{Object at the right-hand side of subtraction}}
 139 };
 140
 141 int f11() {
 142   struct S1 s; // expected-note{{Object at the left-hand side of subtraction}}
 143   return (char *)&s - (char *)&s.b; // expected-warning{{Subtraction of two pointers that}}
 144 }
 145
 146 struct S2 {
 147   char *p1;
 148   char *p2;
 149 };
 150
 151 void init_S2(struct S2 *);
 152
 153 int f12() {
 154   struct S2 s;
 155   init_S2(&s);
 156   return s.p1 - s.p2; // no-warning (pointers are unknown)
 157 }