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src/as/lexer.c: guard against integer overflow (emitting a warning)

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This commit is contained in:
Henrik Hautakoski 2018-12-17 21:34:57 +01:00
parent e75349e7f9
commit 74ecdfc2ab
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GPG key ID: 839F3A7EAFAEAFAA
1 changed files with 39 additions and 16 deletions
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55
src/as/lexer.c
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@ -70,7 +70,7 @@ static int read_next(struct lexer *lex) {
return c;
}
static int read_hex(FILE *fp) {
static int read_hex(FILE *fp, int *out) {
int c, val = 0;
@ -89,11 +89,18 @@ static int read_hex(FILE *fp) {
}
val = (val * 16) + n;
if (val > 0xFF)
goto overflow;
}
return val;
*out = val;
return 0;
overflow:
*out = 0xFF;
return -1;
}
static int read_dec(FILE *fp, int neg) {
static int read_dec(FILE *fp, int neg, int *out) {
int c, val = 0;
@ -103,14 +110,23 @@ static int read_dec(FILE *fp, int neg) {
break;
}
val = (val * 10) + (c - '0');
// Cool trick here.
// because the range is -128 (0x80) to +127 (0x7F)
// We can do 0x80 - 1 if it is NOT a negative number.
if (val > (0x80 - !neg))
goto overflow;
}
if (neg)
return -1 * val;
return val;
*out = neg ? -1 * val : val;
return 0;
overflow:
*out = neg ? -1 * 0x80 : 0x7F;
return -1;
}
static int read_number(FILE *fp) {
static int read_number(FILE *fp, int *out) {
int neg = 0, c = fgetc(fp);
@ -119,7 +135,7 @@ static int read_number(FILE *fp) {
c = fgetc(fp);
if (c == 'x') {
// We have a hexadecimal number.
return read_hex(fp);
return read_hex(fp, out);
}
ungetc(c, fp);
ungetc('0', fp);
@ -133,7 +149,18 @@ static int read_number(FILE *fp) {
ungetc(c, fp);
}
return read_dec(fp, neg);
return read_dec(fp, neg, out);
}
static int parse_number(struct lexer *lex) {
int num;
if (read_number(lex->fp, &num) < 0)
fprintf(stderr, "WARNING: Value truncated on line: %i\n", lex->lineno);
lex->token.value.n = num;
return 0;
}
static int read_string(FILE *fp, char *buf, size_t len) {
@ -195,19 +222,15 @@ int lexer_get_next(struct lexer *lex) {
break;
case '$' :
lex->token.type = TOKEN_REG;
num = read_number(lex->fp);
// Registers is 8-bit only.
if (num > 0xF) {
fprintf(stderr, "ERROR: Invalid register value '%i' on line: %i\n", num, lex->lineno);
if (parse_number(lex) < 0)
return -1;
}
lex->token.value.n = num;
break;
default:
if (first_number(ch)) {
ungetc(ch, lex->fp);
lex->token.type = TOKEN_NUMBER;
lex->token.value.n = read_number(lex->fp);
if (parse_number(lex) < 0)
return -1;
} else if (first_string(ch)) {
char buf[32];
ungetc(ch, lex->fp);