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111
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1 // Verify the correctness of folding relational expressions involving
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2 // pointers to array elements and struct data members and null pointers.
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3 // Although the C semantics of relational expressions are only defined
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4 // for pointers to objects, C++ makes them well-defined when
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5 // (nullptr < p) yields true. See the discussion of the patch for
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6 // c++/67376 on gcc-patches for additional background.
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7
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8 // { dg-do compile { target c++11 } }
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131
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9 // { dg-options "-O1 -fdelete-null-pointer-checks -fdump-tree-optimized" }
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111
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10
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11 // Runtime assert. Used for potentially invalid expressions.
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12 #define RA(e) ((e) ? (void)0 : __builtin_abort ())
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13
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14 // Static assert. Used for valid core constant expressions.
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15 #define SA(e) static_assert ((e), #e)
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16
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17 void test_first_array_element ()
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18 {
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19 static constexpr int a[] = { 0 };
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20 constexpr const int *null = 0;
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21 constexpr const int *pi = a;
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22
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23 // The following are valid constant expressions since in &*pi
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24 // the '&*' "cancel each other out."
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25 SA (!(null == &*pi));
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26 SA ( (null != &*pi));
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27
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28 // The validity of the relational expressions involving null
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29 // pointers in a constexpr context is questionable. Use a run
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30 // time assertion to verify these.
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31 RA ( (null < &*pi));
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32 RA ( (null <= &*pi));
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33 RA (!(null > &*pi));
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34 RA (!(null >= &*pi));
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35
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36 SA (!(&*pi == null));
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37 SA ( (&*pi != null));
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38 RA (!(&*pi < null));
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39 RA (!(&*pi <= null));
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40 RA ( (&*pi > null));
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41 RA ( (&*pi >= null));
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42
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43 // The following are valid constant expressions since &pi [0] is
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44 // equivalent to &*pi.
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45 SA (!(null == &pi [0]));
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46 SA ( (null != &pi [0]));
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47 RA ( (null < &pi [0]));
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48 RA ( (null <= &pi [0]));
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49 RA (!(null > &pi [0]));
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50 RA (!(null >= &pi [0]));
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51
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52 SA (!(&pi [0] == null));
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53 SA ( (&pi [0] != null));
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54 RA (!(&pi [0] < null));
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55 RA (!(&pi [0] <= null));
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56 RA ( (&pi [0] > null));
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57 RA ( (&pi [0] >= null));
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58 }
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59
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60 void test_first_null_array_element ()
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61 {
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62 constexpr const int *pi = 0;
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63 constexpr const int *qi = 0;
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64
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65 // The following are valid constant expressions since in &*qi
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66 // the '&*' "cancel each other out."
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67 SA ( (pi == &*qi));
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68 SA (!(pi != &*qi));
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69
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70 // The validity of the relational expressions involving null
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71 // pointers in a constexpr context is questionable.
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72 RA (!(pi < &*qi));
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73 RA ( (pi <= &*qi));
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74 RA (!(pi > &*qi));
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75 RA ( (pi >= &*qi));
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76
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77 SA ( (&*qi == pi));
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78 SA (!(&*qi != pi));
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79 RA (!(&*qi < pi));
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80 RA ( (&*qi <= pi));
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81 RA (!(&*qi > pi));
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82 RA ( (&*qi >= pi));
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83
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84 // The following are valid constant expressions since &qi [0] is
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85 // equivalent to &*qi.
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86 SA ( (pi == &qi [0]));
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87 SA (!(pi != &qi [0]));
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88 RA (!(pi < &qi [0]));
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89 RA ( (pi <= &qi [0]));
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90 RA (!(pi > &qi [0]));
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91 RA ( (pi >= &qi [0]));
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92
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93 SA ( (&qi [0] == pi));
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94 SA (!(&qi [0] != pi));
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95 RA (!(&qi [0] < pi));
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96 RA ( (&qi [0] <= pi));
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97 RA (!(&qi [0] > pi));
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98 RA ( (&qi [0] >= pi));
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99 }
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100
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101 void test_first_struct_member ()
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102 {
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103 static struct S { int a, b; } s = { 0, 0 };
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104
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105 constexpr const int *p = 0;
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106 constexpr const S *q = &s;
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107
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108 SA (!(p == &q->b));
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109 SA ( (p != &q->b));
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110 RA ( (p < &q->b));
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111 RA ( (p <= &q->b));
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112 RA (!(p > &q->b));
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113 RA (!(p >= &q->b));
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114
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115 SA (!(&q->b == p));
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116 SA ( (&q->b != p));
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117 RA (!(&q->b < p));
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118 RA (!(&q->b <= p));
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119 RA ( (&q->b > p));
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120 RA ( (&q->b >= p));
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121 }
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122
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123 // Expect all runtime asserts to have been eliminated as a result
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124 // of the tested expressions constant folded into true.
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125 // { dg-final { scan-assembler-not "abort" } }
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