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view lwasm/pass2.c @ 577:e49d24f4a9a5
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 | 8764142b3192 |
children |
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/* pass2.c Copyright © 2010 William Astle This file is part of LWTOOLS. LWTOOLS is free software: you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation, either version 3 of the License, or (at your option) any later version. This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details. You should have received a copy of the GNU General Public License along with this program. If not, see <http://www.gnu.org/licenses/>. */ #include <stdio.h> #include <string.h> #include <lw_alloc.h> #include <lw_string.h> #include "lwasm.h" #include "instab.h" /* pass 2: deal with undefined symbols and do a simplification pass on all the expressions. Handle PRAGMA_IMPORTUNDEFEXPORT */ void do_pass2(asmstate_t *as) { line_t *cl; exportlist_t *ex; struct symtabe *s; importlist_t *im; struct line_expr_s *le; // verify the export list if (as -> output_format == OUTPUT_OBJ) { for (ex = as -> exportlist; ex; ex = ex -> next) { s = lookup_symbol(as, NULL, ex -> symbol); if (!s) { if (CURPRAGMA(ex -> line, PRAGMA_IMPORTUNDEFEXPORT)) { for (im = as -> importlist; im; im = im -> next) { if (!strcmp(ex -> symbol, im -> symbol)) break; } if (!im) { im = lw_alloc(sizeof(importlist_t)); im -> symbol = lw_strdup(ex -> symbol); im -> next = as -> importlist; as -> importlist = im; } } else { // undefined export - register error lwasm_register_error(as, ex->line, E_SYMBOL_UNDEFINED_EXPORT); } } ex -> se = s; } if (as -> errorcount > 0) return; } // we want to throw errors on undefined symbols here as -> badsymerr = 1; // now do some reductions on expressions for (cl = as -> line_head; cl; cl = cl -> next) { as -> cl = cl; // simplify address lwasm_reduce_expr(as, cl -> addr); // simplify data address lwasm_reduce_expr(as, cl -> daddr); // simplify each expression for (le = cl -> exprs; le; le = le -> next) lwasm_reduce_expr(as, le -> expr); } }