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annotate lwasm/pass6.c @ 577:e49d24f4a9a5

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Correct bug in the object file output code leading to stack corruption It turns out leaving a pointer to a stack allocated temporary in a persistent data structure is not conducive to correct program operation. Undo the export check setup in the object file output sequence so a pointer to stack allocated memory is not left hanging when the function returns. This seems to correct at least one mysterious crash bug, and possibly others. Thanks to Boisy Pitre for reporting the crash bug that led to this discovery, as well as a previous crash bug that likely has the same root cause. Additional thanks to Ciaran Anscomb whose debugger wielding wizardry revealed the exact location of this particular bit of unbrilliance.
author William Astle <lost@l-w.ca>
date Sat, 03 Aug 2024 14:30:06 -0600
parents 58cafa61ab40
children
Ignore whitespace changes - Everywhere: Within whitespace: At end of lines:
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1 /*
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2 pass6.c
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3
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4 Copyright © 2010 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 #include <stdio.h>
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23 #include <string.h>
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24
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25 #include <lw_alloc.h>
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26 #include <lw_string.h>
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27
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28 #include "lwasm.h"
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29 #include "instab.h"
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30
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31 /*
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32 Finalize Pass
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33
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34 Reduce all expressions in a final pass.
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35
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36 Observation:
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37
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38 Everything should reduce as far as it is going to in a single pass
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39 because all line addresses are now constant (or section-base offset)
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40 */
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41
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42 static int exprok_aux(lw_expr_t e, void *priv)
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43 {
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44 asmstate_t *as = priv;
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45
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46 if (lw_expr_istype(e, lw_expr_type_int))
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47 return 0;
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48
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49 if (as -> output_format == OUTPUT_OBJ || as -> output_format == OUTPUT_LWMOD)
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50 {
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51 if (lw_expr_istype(e, lw_expr_type_oper))
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52 return 0;
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53 if (lw_expr_istype(e, lw_expr_type_special) && (as -> output_format == OUTPUT_OBJ || as -> output_format == OUTPUT_LWMOD))
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54 {
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55 int t;
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56 t = lw_expr_specint(e);
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57 if (t == lwasm_expr_secbase || t == lwasm_expr_syment || t == lwasm_expr_import)
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58 return 0;
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59 }
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60 }
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62 return 1;
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63 }
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65 static int exprok(asmstate_t *as, lw_expr_t e)
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66 {
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67 if (lw_expr_testterms(e, exprok_aux, as))
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68 return 0;
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69 return 1;
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70 }
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73 void do_pass6(asmstate_t *as)
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74 {
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75 line_t *cl;
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76 struct line_expr_s *le;
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77
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78 for (cl = as -> line_head; cl; cl = cl -> next)
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79 {
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80 as -> cl = cl;
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81 for (le = cl -> exprs; le; le = le -> next)
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82 {
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83 lwasm_reduce_expr(as, le -> expr);
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84 if (!exprok(as, le -> expr))
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85 {
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86 lwasm_register_error2(as, cl, E_EXPRESSION_BAD, "%s", lw_expr_print(le -> expr));
0
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87 }
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88 }
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89 }
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90 }