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annotate lwbasic/parser.c @ 32:49d608aecc4d

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Framework for handling local stack frame and/or variables
author lost@l-w.ca
date Thu, 03 Feb 2011 22:00:47 -0700
parents 574931d87abd
children 890a8f688889
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1 /*
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2 compiler.c
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3
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4 Copyright © 2011 William Astle
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5
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6 This file is part of LWTOOLS.
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7
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8 LWTOOLS is free software: you can redistribute it and/or modify it under the
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9 terms of the GNU General Public License as published by the Free Software
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10 Foundation, either version 3 of the License, or (at your option) any later
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11 version.
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12
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13 This program is distributed in the hope that it will be useful, but WITHOUT
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14 ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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15 FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
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16 more details.
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17
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18 You should have received a copy of the GNU General Public License along with
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19 this program. If not, see <http://www.gnu.org/licenses/>.
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20 */
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21
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22 /*
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23 This is the actual compiler bit; it drives the parser and code generation
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24 */
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25
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26 #include <stdio.h>
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27
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28 #include <lw_alloc.h>
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29 #include <lw_string.h>
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30
25
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31 #include "lwbasic.h"
32
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32 #include "symtab.h"
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33
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34
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35 /* size of a type */
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36 static int sizeof_type(int type)
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37 {
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38 /* everything is an "int" right now; 2 bytes */
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39 return 2;
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40 }
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41
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42 /* parse a type; the next token will be acquired as a result */
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43 /* the token advancement is to provide consistency */
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44 static int parse_type(cstate *state)
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45 {
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46 int pt = -1;
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47
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48 switch (state -> lexer_token)
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49 {
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50 case token_kw_integer:
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51 pt = 1;
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52 break;
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53
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54 default:
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55 lwb_error("Invalid type specification");
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56 }
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57 lexer(state);
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58 /* look for "unsigned" modifier for integer types */
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59 return pt;
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60 }
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61
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62 static void parse_decls(cstate *state)
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63 {
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64 /* declarations */
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65 switch (state -> lexer_token)
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66 {
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67 default:
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68 return;
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69 }
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70 }
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71
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72
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73 /* issub means RETURNS is not allowed; !issub means RETURNS is required */
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74
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75 static void parse_subfunc(cstate *state, int issub)
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76 {
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77 int pt, rt;
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78 char *subname, *pn;
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79 int vis = 0;
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80 symtab_entry_t *se;
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81 int paramsize = 0;
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82
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83 state -> local_syms = symtab_init();
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84 state -> framesize = 0;
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85
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86 lexer(state);
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87 if (state -> lexer_token != token_identifier)
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88 {
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89 lwb_error("Invalid sub name '%s'", state -> lexer_token_string);
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90 }
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91
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92 subname = lw_strdup(state -> lexer_token_string);
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93
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94 lexer(state);
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95 if (state -> lexer_token == token_kw_public || state -> lexer_token == token_kw_private)
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96 {
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97 if (state -> lexer_token == token_kw_public)
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98 vis = 1;
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99 lexer(state);
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100 }
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101
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102 /* ignore the "PARAMS" keyword if present */
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103 if (state -> lexer_token == token_kw_params)
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104 lexer(state);
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105
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106 if (state -> lexer_token == token_eol || state -> lexer_token == token_kw_returns)
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107 goto noparms;
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108
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109 paramagain:
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110 if (state -> lexer_token != token_identifier)
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111 {
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112 lwb_error("Parameter name expected, got %s\n", lexer_return_token(state));
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113 }
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114 pn = lw_strdup(state -> lexer_token_string);
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115 lexer(state);
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116
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117 if (state -> lexer_token != token_kw_as)
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118 lwb_error("Expecting AS\n");
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119 lexer(state);
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120
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121 pt = parse_type(state);
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122
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123 se = symtab_find(state -> local_syms, pn);
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124 if (se)
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125 {
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126 lwb_error("Duplicate parameter name %s\n", pn);
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127 }
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128 symtab_register(state -> local_syms, pn, paramsize, symtype_param, NULL);
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129 paramsize += sizeof_type(pt);
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130 lw_free(pn);
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131
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132 if (state -> lexer_token == token_char && state -> lexer_token_string[0] == ',')
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133 {
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134 lexer(state);
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135 goto paramagain;
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136 }
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137
32
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138 noparms:
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139 rt = -1;
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140 if (!issub)
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141 {
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142 if (state -> lexer_token != token_kw_returns)
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143 {
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144 lwb_error("FUNCTION must have RETURNS\n");
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145 }
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146 lexer(state);
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147 /* if (state -> lexer_token == token_identifier)
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148 {
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149 printf("Return value named: %s\n", state -> lexer_token_string);
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150
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151 lexer(state);
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152 if (state -> lexer_token != token_kw_as)
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153 lwb_error("Execting AS after RETURNS");
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154 lexer(state);
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155 }
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156 */
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157 rt = parse_type(state);
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158 }
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159 else
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160 {
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161 if (state -> lexer_token == token_kw_returns)
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162 {
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163 lwb_error("SUB cannot specify RETURNS\n");
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164 }
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165 }
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166
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167
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168 if (state -> lexer_token != token_eol)
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169 {
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170 lwb_error("EOL expected; found %s\n", lexer_return_token(state));
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171 }
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172
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173
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174 se = symtab_find(state -> global_syms, subname);
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175 if (se)
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176 {
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177 lwb_error("Multiply defined symbol %s\n", subname);
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178 }
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179
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180 symtab_register(state -> global_syms, subname, -1, issub ? symtype_sub : symtype_func, NULL);
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181
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182 state -> currentsub = subname;
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183 state -> returntype = rt;
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184 /* consume EOL */
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185 lexer(state);
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186
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187 /* variable declarations */
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188 parse_decls(state);
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189
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190 /* output function/sub prolog */
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191 emit_prolog(state, vis);
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192
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193 /* parse statement block */
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194 /* parse_statements(state); */
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195
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196 if (issub)
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197 {
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198 if (state -> lexer_token != token_kw_endsub)
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199 {
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574931d87abd Created a function to prettyprint the current lexer token
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200 lwb_error("Expecting ENDSUB, got %s\n", lexer_return_token(state));
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201 }
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202 }
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203 else
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204 {
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205 if (state -> lexer_token != token_kw_endfunction)
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206 {
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207 lwb_error("Expecting ENDFUNCTION, got %s\n", lexer_return_token(state));
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208 }
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209 }
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210 /* output function/sub epilog */
32
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211 emit_epilog(state);
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212
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213 lw_free(state -> currentsub);
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214 state -> currentsub = NULL;
32
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215 symtab_destroy(state -> local_syms);
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216 state -> local_syms = NULL;
25
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217 }
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218
30
bcd532a90e53 Renamed "compiler" to "parser" for more consistent terminology
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diff changeset
219 void parser(cstate *state)
25
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220 {
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221 state -> lexer_curchar = -1;
32
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222 state -> global_syms = symtab_init();
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223
25
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224 /* now look for a global declaration */
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225 for (;;)
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226 {
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227 state -> parser_state = parser_state_global;
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228 lexer(state);
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229 switch (state -> lexer_token)
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230 {
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231 case token_kw_function:
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232 printf("Function\n");
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233 parse_subfunc(state, 0);
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234 break;
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235
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236 case token_kw_sub:
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237 printf("Sub\n");
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238 parse_subfunc(state, 1);
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239 break;
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240
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241 /* blank lines are allowed */
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242 case token_eol:
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243 continue;
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244
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245 /* EOF is allowed - end of parsing */
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246 case token_eof:
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247 return;
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248
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249 default:
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574931d87abd Created a function to prettyprint the current lexer token
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250 lwb_error("Invalid token '%s' in global state\n", lexer_return_token(state));
25
87590f43e76d Started lwbasic parser; checkpoint
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251 }
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252 }
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253 }