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freebsd-dev/bin/expr/expr.y
Stefan Eßer 8da97f0057 Fix overflow check for multiplication: 
- Add special test to detect the case of -1 * INTMAX_MIN
- Protect against elimination of the test division by the optimizer

Garrett Cooper noticed that the overflow checks were incomplete, and Bruce
Evans suggested the use of the "volatile" qualifier to counter the effect
of the undefined behaviour, when the prior multiplication caused overflow,
and he also suggested improvements to the comments.

Reviewed by:	bde
MFC after:	1 week
2015-01-27 18:04:41 +00:00

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%{
/*-
* Written by Pace Willisson (pace@blitz.com)
* and placed in the public domain.
*
* Largely rewritten by J.T. Conklin (jtc@wimsey.com)
*
* $FreeBSD$
*/
#include <sys/types.h>
#include <ctype.h>
#include <err.h>
#include <errno.h>
#include <inttypes.h>
#include <limits.h>
#include <locale.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <regex.h>
#include <unistd.h>
/*
* POSIX specifies a specific error code for syntax errors. We exit
* with this code for all errors.
*/
#define ERR_EXIT 2
enum valtype {
integer, numeric_string, string
} ;
struct val {
enum valtype type;
union {
char *s;
intmax_t i;
} u;
} ;
char **av;
int nonposix;
struct val *result;
void assert_to_integer(struct val *);
void assert_div(intmax_t, intmax_t);
void assert_minus(intmax_t, intmax_t, intmax_t);
void assert_plus(intmax_t, intmax_t, intmax_t);
void assert_times(intmax_t, intmax_t, intmax_t);
int compare_vals(struct val *, struct val *);
void free_value(struct val *);
int is_integer(const char *);
int is_string(struct val *);
int is_zero_or_null(struct val *);
struct val *make_integer(intmax_t);
struct val *make_str(const char *);
struct val *op_and(struct val *, struct val *);
struct val *op_colon(struct val *, struct val *);
struct val *op_div(struct val *, struct val *);
struct val *op_eq(struct val *, struct val *);
struct val *op_ge(struct val *, struct val *);
struct val *op_gt(struct val *, struct val *);
struct val *op_le(struct val *, struct val *);
struct val *op_lt(struct val *, struct val *);
struct val *op_minus(struct val *, struct val *);
struct val *op_ne(struct val *, struct val *);
struct val *op_or(struct val *, struct val *);
struct val *op_plus(struct val *, struct val *);
struct val *op_rem(struct val *, struct val *);
struct val *op_times(struct val *, struct val *);
int to_integer(struct val *);
void to_string(struct val *);
int yyerror(const char *);
int yylex(void);
%}
%union
{
struct val *val;
}
%left <val> '|'
%left <val> '&'
%left <val> '=' '>' '<' GE LE NE
%left <val> '+' '-'
%left <val> '*' '/' '%'
%left <val> ':'
%token <val> TOKEN
%type <val> start expr
%%
start: expr { result = $$; }
expr: TOKEN
| '(' expr ')' { $$ = $2; }
| expr '|' expr { $$ = op_or($1, $3); }
| expr '&' expr { $$ = op_and($1, $3); }
| expr '=' expr { $$ = op_eq($1, $3); }
| expr '>' expr { $$ = op_gt($1, $3); }
| expr '<' expr { $$ = op_lt($1, $3); }
| expr GE expr { $$ = op_ge($1, $3); }
| expr LE expr { $$ = op_le($1, $3); }
| expr NE expr { $$ = op_ne($1, $3); }
| expr '+' expr { $$ = op_plus($1, $3); }
| expr '-' expr { $$ = op_minus($1, $3); }
| expr '*' expr { $$ = op_times($1, $3); }
| expr '/' expr { $$ = op_div($1, $3); }
| expr '%' expr { $$ = op_rem($1, $3); }
| expr ':' expr { $$ = op_colon($1, $3); }
;
%%
struct val *
make_integer(intmax_t i)
{
struct val *vp;
vp = (struct val *)malloc(sizeof(*vp));
if (vp == NULL)
errx(ERR_EXIT, "malloc() failed");
vp->type = integer;
vp->u.i = i;
return (vp);
}
struct val *
make_str(const char *s)
{
struct val *vp;
vp = (struct val *)malloc(sizeof(*vp));
if (vp == NULL || ((vp->u.s = strdup(s)) == NULL))
errx(ERR_EXIT, "malloc() failed");
if (is_integer(s))
vp->type = numeric_string;
else
vp->type = string;
return (vp);
}
void
free_value(struct val *vp)
{
if (vp->type == string || vp->type == numeric_string)
free(vp->u.s);
}
int
to_integer(struct val *vp)
{
intmax_t i;
/* we can only convert numeric_string to integer, here */
if (vp->type == numeric_string) {
errno = 0;
i = strtoimax(vp->u.s, (char **)NULL, 10);
/* just keep as numeric_string, if the conversion fails */
if (errno != ERANGE) {
free(vp->u.s);
vp->u.i = i;
vp->type = integer;
}
}
return (vp->type == integer);
}
void
assert_to_integer(struct val *vp)
{
if (vp->type == string)
errx(ERR_EXIT, "not a decimal number: '%s'", vp->u.s);
if (!to_integer(vp))
errx(ERR_EXIT, "operand too large: '%s'", vp->u.s);
}
void
to_string(struct val *vp)
{
char *tmp;
if (vp->type == string || vp->type == numeric_string)
return;
/*
* log_10(x) ~= 0.3 * log_2(x). Rounding up gives the number
* of digits; add one each for the sign and terminating null
* character, respectively.
*/
#define NDIGITS(x) (3 * (sizeof(x) * CHAR_BIT) / 10 + 1 + 1 + 1)
tmp = malloc(NDIGITS(vp->u.i));
if (tmp == NULL)
errx(ERR_EXIT, "malloc() failed");
sprintf(tmp, "%jd", vp->u.i);
vp->type = string;
vp->u.s = tmp;
}
int
is_integer(const char *s)
{
if (nonposix) {
if (*s == '\0')
return (1);
while (isspace((unsigned char)*s))
s++;
}
if (*s == '-' || (nonposix && *s == '+'))
s++;
if (*s == '\0')
return (0);
while (isdigit((unsigned char)*s))
s++;
return (*s == '\0');
}
int
is_string(struct val *vp)
{
/* only TRUE if this string is not a valid integer */
return (vp->type == string);
}
int
yylex(void)
{
char *p;
if (*av == NULL)
return (0);
p = *av++;
if (strlen(p) == 1) {
if (strchr("|&=<>+-*/%:()", *p))
return (*p);
} else if (strlen(p) == 2 && p[1] == '=') {
switch (*p) {
case '>': return (GE);
case '<': return (LE);
case '!': return (NE);
}
}
yylval.val = make_str(p);
return (TOKEN);
}
int
is_zero_or_null(struct val *vp)
{
if (vp->type == integer)
return (vp->u.i == 0);
return (*vp->u.s == 0 || (to_integer(vp) && vp->u.i == 0));
}
int
main(int argc, char *argv[])
{
int c;
setlocale(LC_ALL, "");
if (getenv("EXPR_COMPAT") != NULL
|| check_utility_compat("expr")) {
av = argv + 1;
nonposix = 1;
} else {
while ((c = getopt(argc, argv, "e")) != -1) {
switch (c) {
case 'e':
nonposix = 1;
break;
default:
errx(ERR_EXIT,
"usage: expr [-e] expression\n");
}
}
av = argv + optind;
}
yyparse();
if (result->type == integer)
printf("%jd\n", result->u.i);
else
printf("%s\n", result->u.s);
return (is_zero_or_null(result));
}
int
yyerror(const char *s __unused)
{
errx(ERR_EXIT, "syntax error");
}
struct val *
op_or(struct val *a, struct val *b)
{
if (!is_zero_or_null(a)) {
free_value(b);
return (a);
}
free_value(a);
if (!is_zero_or_null(b))
return (b);
free_value(b);
return (make_integer((intmax_t)0));
}
struct val *
op_and(struct val *a, struct val *b)
{
if (is_zero_or_null(a) || is_zero_or_null(b)) {
free_value(a);
free_value(b);
return (make_integer((intmax_t)0));
} else {
free_value(b);
return (a);
}
}
int
compare_vals(struct val *a, struct val *b)
{
int r;
if (is_string(a) || is_string(b)) {
to_string(a);
to_string(b);
r = strcoll(a->u.s, b->u.s);
} else {
assert_to_integer(a);
assert_to_integer(b);
if (a->u.i > b->u.i)
r = 1;
else if (a->u.i < b->u.i)
r = -1;
else
r = 0;
}
free_value(a);
free_value(b);
return (r);
}
struct val *
op_eq(struct val *a, struct val *b)
{
return (make_integer((intmax_t)(compare_vals(a, b) == 0)));
}
struct val *
op_gt(struct val *a, struct val *b)
{
return (make_integer((intmax_t)(compare_vals(a, b) > 0)));
}
struct val *
op_lt(struct val *a, struct val *b)
{
return (make_integer((intmax_t)(compare_vals(a, b) < 0)));
}
struct val *
op_ge(struct val *a, struct val *b)
{
return (make_integer((intmax_t)(compare_vals(a, b) >= 0)));
}
struct val *
op_le(struct val *a, struct val *b)
{
return (make_integer((intmax_t)(compare_vals(a, b) <= 0)));
}
struct val *
op_ne(struct val *a, struct val *b)
{
return (make_integer((intmax_t)(compare_vals(a, b) != 0)));
}
void
assert_plus(intmax_t a, intmax_t b, intmax_t r)
{
/*
* sum of two positive numbers must be positive,
* sum of two negative numbers must be negative
*/
if ((a > 0 && b > 0 && r <= 0) ||
(a < 0 && b < 0 && r >= 0))
errx(ERR_EXIT, "overflow");
}
struct val *
op_plus(struct val *a, struct val *b)
{
struct val *r;
assert_to_integer(a);
assert_to_integer(b);
r = make_integer(a->u.i + b->u.i);
assert_plus(a->u.i, b->u.i, r->u.i);
free_value(a);
free_value(b);
return (r);
}
void
assert_minus(intmax_t a, intmax_t b, intmax_t r)
{
/* special case subtraction of INTMAX_MIN */
if (b == INTMAX_MIN && a < 0)
errx(ERR_EXIT, "overflow");
/* check addition of negative subtrahend */
assert_plus(a, -b, r);
}
struct val *
op_minus(struct val *a, struct val *b)
{
struct val *r;
assert_to_integer(a);
assert_to_integer(b);
r = make_integer(a->u.i - b->u.i);
assert_minus(a->u.i, b->u.i, r->u.i);
free_value(a);
free_value(b);
return (r);
}
/*
* We depend on undefined behaviour giving a result (in r).
* To test this result, pass it as volatile. This prevents
* optimizing away of the test based on the undefined behaviour.
*/
void
assert_times(intmax_t a, intmax_t b, volatile intmax_t r)
{
/*
* If the first operand is 0, no overflow is possible,
* else the result of the division test must match the
* second operand.
*
* Be careful to avoid overflow in the overflow test, as
* in assert_div(). Overflow in division would kill us
* with a SIGFPE before getting the test wrong. In old
* buggy versions, optimization used to give a null test
* instead of a SIGFPE.
*/
if ((a == -1 && b == INTMAX_MIN) || (a != 0 && r / a != b))
errx(ERR_EXIT, "overflow");
}
struct val *
op_times(struct val *a, struct val *b)
{
struct val *r;
assert_to_integer(a);
assert_to_integer(b);
r = make_integer(a->u.i * b->u.i);
assert_times(a->u.i, b->u.i, r->u.i);
free_value(a);
free_value(b);
return (r);
}
void
assert_div(intmax_t a, intmax_t b)
{
if (b == 0)
errx(ERR_EXIT, "division by zero");
/* only INTMAX_MIN / -1 causes overflow */
if (a == INTMAX_MIN && b == -1)
errx(ERR_EXIT, "overflow");
}
struct val *
op_div(struct val *a, struct val *b)
{
struct val *r;
assert_to_integer(a);
assert_to_integer(b);
/* assert based on operands only, not on result */
assert_div(a->u.i, b->u.i);
r = make_integer(a->u.i / b->u.i);
free_value(a);
free_value(b);
return (r);
}
struct val *
op_rem(struct val *a, struct val *b)
{
struct val *r;
assert_to_integer(a);
assert_to_integer(b);
/* pass a=1 to only check for div by zero */
assert_div(1, b->u.i);
r = make_integer(a->u.i % b->u.i);
free_value(a);
free_value(b);
return (r);
}
struct val *
op_colon(struct val *a, struct val *b)
{
regex_t rp;
regmatch_t rm[2];
char errbuf[256];
int eval;
struct val *v;
/* coerce both arguments to strings */
to_string(a);
to_string(b);
/* compile regular expression */
if ((eval = regcomp(&rp, b->u.s, 0)) != 0) {
regerror(eval, &rp, errbuf, sizeof(errbuf));
errx(ERR_EXIT, "%s", errbuf);
}
/* compare string against pattern */
/* remember that patterns are anchored to the beginning of the line */
if (regexec(&rp, a->u.s, (size_t)2, rm, 0) == 0 && rm[0].rm_so == 0)
if (rm[1].rm_so >= 0) {
*(a->u.s + rm[1].rm_eo) = '\0';
v = make_str(a->u.s + rm[1].rm_so);
} else
v = make_integer((intmax_t)(rm[0].rm_eo));
else
if (rp.re_nsub == 0)
v = make_integer((intmax_t)0);
else
v = make_str("");
/* free arguments and pattern buffer */
free_value(a);
free_value(b);
regfree(&rp);
return (v);
}
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