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view lwasm/os9.c @ 434:052c5f335a92
Fix bug in like terms collection in expression simplification
Like term collection would lose the actual "variable" part of the term if
the second term collected happened to have no coefficient. This would cause
the expression to take the value of the calculated coefficient which is
obviously wrong.
Thanks to hider <stego@satx.rr.com> for reporting the bug and providing a
proper test case.
Observation: this bug has been present since the first pre-release of
lwtools 3.0 when the algebraic expression system was introduced. Apparently
people tend not to create expressions that trigger the like terms handler.
The specific conditions require the symbol to be undefined and the second
operand to the addition has to have no coefficient so it's likely a fairly
rare scenario. Still, it is somewhat surprising that nobody tripped on it
before now.
author | William Astle <lost@l-w.ca> |
---|---|
date | Mon, 23 Jan 2017 22:58:36 -0700 |
parents | 8764142b3192 |
children | 928c033c0cd0 |
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/* os9.c Copyright © 2009 William Astle This file is part of LWASM. LWASM 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/>. This file implements the various pseudo operations related to OS9 target */ #include <errno.h> #include <stdio.h> #include <stdlib.h> #include <string.h> #include <lw_expr.h> #include "lwasm.h" #include "instab.h" // OS9 syscall PARSEFUNC(pseudo_parse_os9) { lw_expr_t e; if (as -> output_format != OUTPUT_OS9 && as -> output_format != OUTPUT_OBJ) { lwasm_register_error2(as, l, E_DIRECTIVE_OS9_ONLY, "%s", "os9"); return; } // fetch immediate value e = lwasm_parse_expr(as, p); if (!e) { lwasm_register_error(as, l, E_OPERAND_BAD); return; } lwasm_save_expr(l, 0, e); l -> len = 3; } EMITFUNC(pseudo_emit_os9) { lw_expr_t e; e = lwasm_fetch_expr(l, 0); lwasm_emitop(l, 0x103f); lwasm_emitexpr(l, e, 1); } PARSEFUNC(pseudo_parse_mod) { lw_expr_t e; int i; if (as -> output_format != OUTPUT_OS9) { lwasm_register_error2(as, l, E_DIRECTIVE_OS9_ONLY, "%s", "mod"); skip_operand(p); return; } if (as -> inmod) { lwasm_register_error(as, l, E_MODULE_IN); skip_operand(p); return; } // parse 6 expressions... for (i = 0; i < 5; i++) { e = lwasm_parse_expr(as, p); if (!e) { lwasm_register_error(as, l, E_OPERAND_BAD); return; } lwasm_save_expr(l, i, e); if (**p != ',') { lwasm_register_error(as, l, E_OPERAND_BAD); return; } (*p)++; } e = lwasm_parse_expr(as, p); if (!e) { lwasm_register_error(as, l, E_OPERAND_BAD); return; } lwasm_save_expr(l, 5, e); l -> inmod = 1; // we have an implicit ORG 0 with "mod" lw_expr_destroy(l -> addr); l -> addr = lw_expr_build(lw_expr_type_int, 0); // likewise for data pointer lw_expr_destroy(l -> daddr); l -> daddr = lw_expr_build(lw_expr_type_int, 0); // init crc as -> inmod = 1; l -> len = 13; } EMITFUNC(pseudo_emit_mod) { lw_expr_t e1, e2, e3, e4; int csum; as -> crc[0] = 0xff; as -> crc[1] = 0xff; as -> crc[2] = 0xff; // sync bytes lwasm_emit(l, 0x87); lwasm_emit(l, 0xcd); // mod length lwasm_emitexpr(l, e1 = lwasm_fetch_expr(l, 0), 2); // name offset lwasm_emitexpr(l, e2 = lwasm_fetch_expr(l, 1), 2); // type lwasm_emitexpr(l, e3 = lwasm_fetch_expr(l, 2), 1); // flags/rev lwasm_emitexpr(l, e4 = lwasm_fetch_expr(l, 3), 1); // header check csum = ~(0x87 ^ 0xCD ^(lw_expr_intval(e1) >> 8) ^ (lw_expr_intval(e1) & 0xff) ^ (lw_expr_intval(e2) >> 8) ^ (lw_expr_intval(e2) & 0xff) ^ lw_expr_intval(e3) ^ lw_expr_intval(e4)); lwasm_emit(l, csum); // module type specific output // note that these are handled the same for all so // there need not be any special casing // exec offset or fmgr name offset lwasm_emitexpr(l, lwasm_fetch_expr(l, 4), 2); // data size or drvr name offset lwasm_emitexpr(l, lwasm_fetch_expr(l, 5), 2); } PARSEFUNC(pseudo_parse_emod) { skip_operand(p); if (as -> output_format != OUTPUT_OS9) { lwasm_register_error2(as, l, E_DIRECTIVE_OS9_ONLY, "%s", "emod"); return; } if (!(as -> inmod)) { lwasm_register_error(as, l, E_MODULE_NOTIN); return; } as -> inmod = 0; l -> len = 3; } EMITFUNC(pseudo_emit_emod) { unsigned char tcrc[3]; // don't mess with CRC! tcrc[0] = as -> crc[0] ^ 0xff; tcrc[1] = as -> crc[1] ^ 0xff; tcrc[2] = as -> crc[2] ^ 0xff; lwasm_emit(l, tcrc[0]); lwasm_emit(l, tcrc[1]); lwasm_emit(l, tcrc[2]); }