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view lwcc/cc-gencode.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 | 59b8c8b15bd4 |
children |
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/* lwcc/cc-gencode.c Copyright © 2019 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 <stdlib.h> #include <string.h> #include <lw_alloc.h> #include <lw_string.h> #include "tree.h" char *generate_nextlabel(void) { static int labelnum = 0; char buf[16]; sprintf(buf, "L%d", labelnum++); return lw_strdup(buf); } void generate_code(node_t *n, FILE *output); void generate_code_shift(node_t *n, FILE *output, int dir) { generate_code(n -> children, output); if (n -> children -> next_child -> type == NODE_CONST_INT) { long ival; int i; ival = strtol(n -> children -> next_child -> strval, NULL, 0); if (ival <= 0) return; if (ival >= 16) { fprintf(output, "\tldd #%d\n", dir == 1 ? 0 : -1); return; } if (ival >= 8) { if (dir == 1) { fprintf(output, "\ttfr b,a\n\tclrb\n"); for (i = ival - 8; i > 0; i--) { fprintf(output, "\tlsla\n"); } } else { fprintf(output, "\ttfr a,b\n\tsex\n"); for (i = ival - 8; i > 0; i--) { fprintf(output, "\tasrb\n"); } } return; } for (i = ival; i > 0; i--) { if (dir == 1) { fprintf(output, "\taslb\n\trola\n"); } else { fprintf(output, "\tasra\n\trorb\n"); } } return; } else { fprintf(output, "\tpshs d\n"); generate_code(n -> children -> next_child, output); fprintf(output, "\tjsr ___%ssh16\n\tpuls d\n", dir == 1 ? "l" : "r"); } } void generate_code(node_t *n, FILE *output) { node_t *nn; char *label1, *label2; switch (n -> type) { // function definition - output prologue, then statements, then epilogue case NODE_FUNDEF: fprintf(output, "\tsection .text\n\texport _%s\n_%s\n", n->children->next_child->strval, n->children->next_child->strval); generate_code(n->children->next_child->next_child->next_child, output); fprintf(output, "\trts\n"); break; case NODE_CONST_INT: fprintf(output, "\tldd #%s\n", n->strval); break; case NODE_OPER_PLUS: generate_code(n->children, output); fprintf(output, "\tpshs d\n"); generate_code(n->children->next_child, output); fprintf(output, "\taddd ,s++\n"); break; case NODE_OPER_MINUS: generate_code(n->children, output); fprintf(output, "\tpshs d,x\n"); generate_code(n->children->next_child, output); fprintf(output, "\tstd 2,s\n\tpuls d\n\tsubd ,s++\n"); break; case NODE_OPER_TIMES: generate_code(n -> children, output); fprintf(output, "\tpshs d\n"); generate_code(n->children->next_child, output); fprintf(output, "\tjsr ___mul16i\n\tpuls d\n"); break; case NODE_OPER_DIVIDE: generate_code(n -> children, output); fprintf(output, "\tpshs d\n"); generate_code(n->children->next_child, output); fprintf(output, "\tjsr ___div16i\n\tpuls d\n"); break; case NODE_OPER_MOD: generate_code(n -> children, output); fprintf(output, "\tpshs d\n"); generate_code(n -> children -> next_child, output); fprintf(output, "\tjsr ___mod16i\n\tpuls d\n"); break; case NODE_OPER_LSH: generate_code_shift(n, output, 1); break; case NODE_OPER_RSH: generate_code_shift(n, output, 0); break; case NODE_OPER_COND: label1 = generate_nextlabel(); label2 = generate_nextlabel(); generate_code(n -> children, output); fprintf(output, "\tsubd #0\n\tbeq %s\n", label1); generate_code(n -> children -> next_child, output); fprintf(output, "\tbra %s\n%s\n", label2, label1); generate_code(n -> children -> next_child -> next_child, output); fprintf(output, "%s\n", label2); lw_free(label1); lw_free(label2); break; case NODE_OPER_COMMA: generate_code(n -> children, output); generate_code(n -> children -> next_child, output); break; case NODE_OPER_BWAND: generate_code(n -> children, output); fprintf(output, "\tpshs d\n"); generate_code(n -> children -> next_child, output); fprintf(output, "\tandb 1,s\n\tanda ,s++\n"); break; case NODE_OPER_BWOR: generate_code(n -> children, output); fprintf(output, "\tpshs d\n"); generate_code(n -> children -> next_child, output); fprintf(output, "\torb 1,s\n\tora ,s++\n"); break; case NODE_OPER_BWXOR: generate_code(n -> children, output); fprintf(output, "\tpshs d\n"); generate_code(n -> children -> next_child, output); fprintf(output, "\teorb 1,s\n\teora ,s++\n"); break; case NODE_OPER_BAND: label1 = generate_nextlabel(); generate_code(n -> children, output); fprintf(output, "\tsubd #0\n\tbeq %s\n", label1); generate_code(n -> children -> next_child, output); fprintf(output, "\tsubd #0\n\tbeq %s\n\tldd #1\n%s\n", label1, label1); lw_free(label1); break; case NODE_OPER_BOR: label1 = generate_nextlabel(); label2 = generate_nextlabel(); generate_code(n -> children, output); fprintf(output, "\tsubd #0\n\tbne %s\n", label1); generate_code(n -> children -> next_child, output); fprintf(output, "\tsubd #0\n\tbeq %s\n%s\tldd #1\n%s\n", label2, label1, label2); lw_free(label1); lw_free(label2); break; case NODE_OPER_NE: case NODE_OPER_EQ: case NODE_OPER_LT: case NODE_OPER_GT: case NODE_OPER_LE: case NODE_OPER_GE: generate_code(n -> children, output); fprintf(output, "\tpshs d\n"); generate_code(n -> children -> next_child, output); fprintf(output, "\tsubd ,s++\n"); label1 = generate_nextlabel(); label2 = generate_nextlabel(); fprintf(output, "\t%s %s\n", ( (n -> type == NODE_OPER_NE ? "bne" : (n -> type == NODE_OPER_EQ ? "beq" : (n -> type == NODE_OPER_LT ? "bge" : (n -> type == NODE_OPER_GT ? "ble" : (n -> type == NODE_OPER_LE ? "bgt" : (n -> type == NODE_OPER_GE ? "blt" : "foobar")))))) ), label1); fprintf(output, "\tldd #0\n\tbra %s\n%s\tldd #1\n%s\n", label2, label1, label2); lw_free(label1); lw_free(label2); break; default: for (nn = n -> children; nn; nn = nn -> next_child) generate_code(nn, output); break; } }