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72
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1 module dmd.NullExp;
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2
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114
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3 import dmd.common;
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72
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4 import dmd.Expression;
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5 import dmd.backend.elem;
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6 import dmd.InterState;
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7 import dmd.MATCH;
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8 import dmd.Type;
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9 import dmd.TY;
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10 import dmd.TypeTypedef;
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11 import dmd.OutBuffer;
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12 import dmd.Loc;
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13 import dmd.Scope;
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14 import dmd.IRState;
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15 import dmd.HdrGenState;
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16 import dmd.TOK;
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17 import dmd.backend.dt_t;
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18 import dmd.backend.Util;
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19
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0
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20 class NullExp : Expression
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21 {
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22 ubyte committed;
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23
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24 this(Loc loc)
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72
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25 {
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0
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26 super(loc, TOK.TOKnull, NullExp.sizeof);
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27 }
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28
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29 override Expression semantic(Scope sc)
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30 {
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31 version (LOGSEMANTIC) {
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32 printf("NullExp.semantic('%s')\n", toChars());
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33 }
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34 // null is the same as (void*)0
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35 if (!type)
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36 type = Type.tvoid.pointerTo();
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37
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38 return this;
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39 }
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40
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72
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41 override bool isBool(bool result)
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0
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42 {
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43 assert(false);
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44 }
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45
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46 override int isConst()
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0
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47 {
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63
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48 return 0;
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0
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49 }
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50
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72
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51 override void toCBuffer(OutBuffer buf, HdrGenState* hgs)
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0
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52 {
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53 buf.writestring("null");
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54 }
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55
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72
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56 override void toMangleBuffer(OutBuffer buf)
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0
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57 {
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64
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58 buf.writeByte('n');
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0
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59 }
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60
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61 override MATCH implicitConvTo(Type t)
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62 {
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63 static if (false) {
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64 printf("NullExp.implicitConvTo(this=%s, type=%s, t=%s, committed = %d)\n",
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65 toChars(), type.toChars(), t.toChars(), committed);
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66 }
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67 if (this.type.equals(t))
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68 return MATCH.MATCHexact;
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69
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70 /* Allow implicit conversions from invariant to mutable|const,
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71 * and mutable to invariant. It works because, after all, a null
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72 * doesn't actually point to anything.
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73 */
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74 if (t.invariantOf().equals(type.invariantOf()))
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75 return MATCH.MATCHconst;
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76
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77 // null implicitly converts to any pointer type or dynamic array
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78 if (type.ty == TY.Tpointer && type.nextOf().ty == TY.Tvoid)
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79 {
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80 if (t.ty == TY.Ttypedef)
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81 t = (cast(TypeTypedef)t).sym.basetype;
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82 if (t.ty == TY.Tpointer || t.ty == TY.Tarray ||
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83 t.ty == TY.Taarray || t.ty == TY.Tclass ||
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84 t.ty == TY.Tdelegate)
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85 {
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86 return committed ? MATCH.MATCHconvert : MATCH.MATCHexact;
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87 }
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88 }
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89
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90 return Expression.implicitConvTo(t);
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91 }
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92
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72
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93 override Expression castTo(Scope sc, Type t)
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94 {
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95 NullExp e;
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96 Type tb;
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97
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98 //printf("NullExp::castTo(t = %p)\n", t);
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99 if (type is t)
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100 {
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101 committed = 1;
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102 return this;
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103 }
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104
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105 e = cast(NullExp)copy();
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106 e.committed = 1;
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107 tb = t.toBasetype();
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108 e.type = type.toBasetype();
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109
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110 if (tb !is e.type)
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111 {
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112 // null implicitly converts to any pointer type or dynamic array
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113 if (e.type.ty == TY.Tpointer && e.type.nextOf().ty == TY.Tvoid &&
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114 (tb.ty == TY.Tpointer || tb.ty == TY.Tarray || tb.ty == TY.Taarray ||
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115 tb.ty == TY.Tdelegate))
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116 {
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117 static if (false) {
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118 if (tb.ty == TY.Tdelegate)
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119 {
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120 TypeDelegate td = cast(TypeDelegate)tb;
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121 TypeFunction tf = cast(TypeFunction)td.nextOf();
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122
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123 if (!tf.varargs && !(tf.arguments && tf.arguments.dim))
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124 {
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125 return Expression.castTo(sc, t);
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126 }
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127 }
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128 }
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129 }
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130 else
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131 {
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132 return e.Expression.castTo(sc, t);
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133 }
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134 }
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135 e.type = t;
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136 return e;
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137 }
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138
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72
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139 override Expression interpret(InterState istate)
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0
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140 {
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123
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141 return this;
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142 }
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143
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72
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144 override elem* toElem(IRState* irs)
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0
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145 {
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146 return el_long(type.totym(), 0);
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147 }
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148
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72
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149 override dt_t** toDt(dt_t** pdt)
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0
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150 {
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72
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151 assert(type);
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0
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152 return dtnzeros(pdt, cast(uint)type.size());
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153 }
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154 }
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155
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