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1 module dmd.NullExp;
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2
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3 import dmd.Expression;
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4 import dmd.backend.elem;
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5 import dmd.InterState;
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6 import dmd.MATCH;
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7 import dmd.Type;
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8 import dmd.TY;
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9 import dmd.TypeTypedef;
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10 import dmd.OutBuffer;
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11 import dmd.Loc;
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12 import dmd.Scope;
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13 import dmd.IRState;
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14 import dmd.HdrGenState;
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15 import dmd.TOK;
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16 import dmd.backend.dt_t;
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17 import dmd.backend.Util;
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18
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19 class NullExp : Expression
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20 {
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21 ubyte committed;
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22
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23 this(Loc loc)
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24 {
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25 super(loc, TOK.TOKnull, NullExp.sizeof);
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26 }
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27
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28 Expression semantic(Scope sc)
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29 {
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30 version (LOGSEMANTIC) {
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31 printf("NullExp.semantic('%s')\n", toChars());
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32 }
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33 // null is the same as (void*)0
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34 if (!type)
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35 type = Type.tvoid.pointerTo();
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36
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37 return this;
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38 }
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39
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40 bool isBool(bool result)
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41 {
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42 assert(false);
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43 }
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44
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45 int isConst()
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46 {
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47 assert(false);
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48 }
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49
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50 void toCBuffer(OutBuffer buf, HdrGenState* hgs)
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51 {
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52 buf.writestring("null");
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53 }
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54
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55 void toMangleBuffer(OutBuffer buf)
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56 {
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57 assert(false);
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58 }
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59
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60 MATCH implicitConvTo(Type t)
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61 {
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62 static if (false) {
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63 printf("NullExp.implicitConvTo(this=%s, type=%s, t=%s, committed = %d)\n",
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64 toChars(), type.toChars(), t.toChars(), committed);
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65 }
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66 if (this.type.equals(t))
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67 return MATCH.MATCHexact;
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68
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69 /* Allow implicit conversions from invariant to mutable|const,
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70 * and mutable to invariant. It works because, after all, a null
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71 * doesn't actually point to anything.
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72 */
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73 if (t.invariantOf().equals(type.invariantOf()))
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74 return MATCH.MATCHconst;
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75
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76 // null implicitly converts to any pointer type or dynamic array
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77 if (type.ty == TY.Tpointer && type.nextOf().ty == TY.Tvoid)
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78 {
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79 if (t.ty == TY.Ttypedef)
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80 t = (cast(TypeTypedef)t).sym.basetype;
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81 if (t.ty == TY.Tpointer || t.ty == TY.Tarray ||
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82 t.ty == TY.Taarray || t.ty == TY.Tclass ||
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83 t.ty == TY.Tdelegate)
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84 {
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85 return committed ? MATCH.MATCHconvert : MATCH.MATCHexact;
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86 }
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87 }
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88
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89 return Expression.implicitConvTo(t);
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90 }
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91
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92 Expression castTo(Scope sc, Type t)
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93 {
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94 NullExp e;
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95 Type tb;
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96
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97 //printf("NullExp::castTo(t = %p)\n", t);
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98 if (type is t)
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99 {
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100 committed = 1;
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101 return this;
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102 }
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103
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104 e = cast(NullExp)copy();
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105 e.committed = 1;
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106 tb = t.toBasetype();
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107 e.type = type.toBasetype();
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108
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109 if (tb !is e.type)
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110 {
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111 // null implicitly converts to any pointer type or dynamic array
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112 if (e.type.ty == TY.Tpointer && e.type.nextOf().ty == TY.Tvoid &&
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113 (tb.ty == TY.Tpointer || tb.ty == TY.Tarray || tb.ty == TY.Taarray ||
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114 tb.ty == TY.Tdelegate))
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115 {
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116 static if (false) {
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117 if (tb.ty == TY.Tdelegate)
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118 {
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119 TypeDelegate td = cast(TypeDelegate)tb;
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120 TypeFunction tf = cast(TypeFunction)td.nextOf();
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121
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122 if (!tf.varargs && !(tf.arguments && tf.arguments.dim))
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123 {
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124 return Expression.castTo(sc, t);
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125 }
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126 }
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127 }
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128 }
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129 else
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130 {
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131 return e.Expression.castTo(sc, t);
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132 }
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133 }
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134 e.type = t;
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135 return e;
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136 }
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137
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138 Expression interpret(InterState* istate)
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139 {
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140 assert(false);
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141 }
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142
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143 elem* toElem(IRState* irs)
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144 {
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145 return el_long(type.totym(), 0);
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146 }
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147
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148 dt_t** toDt(dt_t** pdt)
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149 {
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150 assert(type);
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151 return dtnzeros(pdt, cast(uint)type.size());
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152 }
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153 }
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154
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