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expr.c
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expr.c
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/* expr.c -- arithmetic expression evaluation. */
/* Copyright (C) 1990-2020 Free Software Foundation, Inc.
This file is part of GNU Bash, the Bourne Again SHell.
Bash 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.
Bash 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 Bash. If not, see <http://www.gnu.org/licenses/>.
*/
/*
All arithmetic is done as intmax_t integers with no checking for overflow
(though division by 0 is caught and flagged as an error).
The following operators are handled, grouped into a set of levels in
order of decreasing precedence.
"id++", "id--" [post-increment and post-decrement]
"-", "+" [(unary operators)]
"++id", "--id" [pre-increment and pre-decrement]
"!", "~"
"**" [(exponentiation)]
"*", "/", "%"
"+", "-"
"<<", ">>"
"<=", ">=", "<", ">"
"==", "!="
"&"
"^"
"|"
"&&"
"||"
"expr ? expr : expr"
"=", "*=", "/=", "%=", "+=", "-=", "<<=", ">>=", "&=", "^=", "|="
, [comma]
(Note that most of these operators have special meaning to bash, and an
entire expression should be quoted, e.g. "a=$a+1" or "a=a+1" to ensure
that it is passed intact to the evaluator when using `let'. When using
the $[] or $(( )) forms, the text between the `[' and `]' or `((' and `))'
is treated as if in double quotes.)
Sub-expressions within parentheses have a precedence level greater than
all of the above levels and are evaluated first. Within a single prece-
dence group, evaluation is left-to-right, except for the arithmetic
assignment operator (`='), which is evaluated right-to-left (as in C).
The expression evaluator returns the value of the expression (assignment
statements have as a value what is returned by the RHS). The `let'
builtin, on the other hand, returns 0 if the last expression evaluates to
a non-zero, and 1 otherwise.
Implementation is a recursive-descent parser.
Chet Ramey
*/
#include "config.h"
#include <stdio.h>
#include "bashansi.h"
#if defined (HAVE_UNISTD_H)
# ifdef _MINIX
# include <sys/types.h>
# endif
# include <unistd.h>
#endif
#include "chartypes.h"
#include "bashintl.h"
#include "shell.h"
#include "arrayfunc.h"
#include "execute_cmd.h"
#include "flags.h"
#include "subst.h"
#include "typemax.h" /* INTMAX_MAX, INTMAX_MIN */
/* Because of the $((...)) construct, expressions may include newlines.
Here is a macro which accepts newlines, tabs and spaces as whitespace. */
#define cr_whitespace(c) (whitespace(c) || ((c) == '\n'))
/* Size be which the expression stack grows when necessary. */
#define EXPR_STACK_GROW_SIZE 10
/* Maximum amount of recursion allowed. This prevents a non-integer
variable such as "num=num+2" from infinitely adding to itself when
"let num=num+2" is given. */
#define MAX_EXPR_RECURSION_LEVEL 1024
/* The Tokens. Singing "The Lion Sleeps Tonight". */
#define EQEQ 1 /* "==" */
#define NEQ 2 /* "!=" */
#define LEQ 3 /* "<=" */
#define GEQ 4 /* ">=" */
#define STR 5 /* string */
#define NUM 6 /* number */
#define LAND 7 /* "&&" Logical AND */
#define LOR 8 /* "||" Logical OR */
#define LSH 9 /* "<<" Left SHift */
#define RSH 10 /* ">>" Right SHift */
#define OP_ASSIGN 11 /* op= expassign as in Posix.2 */
#define COND 12 /* exp1 ? exp2 : exp3 */
#define POWER 13 /* exp1**exp2 */
#define PREINC 14 /* ++var */
#define PREDEC 15 /* --var */
#define POSTINC 16 /* var++ */
#define POSTDEC 17 /* var-- */
#define EQ '='
#define GT '>'
#define LT '<'
#define PLUS '+'
#define MINUS '-'
#define MUL '*'
#define DIV '/'
#define MOD '%'
#define NOT '!'
#define LPAR '('
#define RPAR ')'
#define BAND '&' /* Bitwise AND */
#define BOR '|' /* Bitwise OR. */
#define BXOR '^' /* Bitwise eXclusive OR. */
#define BNOT '~' /* Bitwise NOT; Two's complement. */
#define QUES '?'
#define COL ':'
#define COMMA ','
/* This should be the function corresponding to the operator with the
highest precedence. */
#define EXP_HIGHEST expcomma
#ifndef MAX_INT_LEN
# define MAX_INT_LEN 32
#endif
struct lvalue
{
char *tokstr; /* possibly-rewritten lvalue if not NULL */
intmax_t tokval; /* expression evaluated value */
SHELL_VAR *tokvar; /* variable described by array or var reference */
intmax_t ind; /* array index if not -1 */
};
/* A structure defining a single expression context. */
typedef struct {
int curtok, lasttok;
char *expression, *tp, *lasttp;
intmax_t tokval;
char *tokstr;
int noeval;
struct lvalue lval;
} EXPR_CONTEXT;
static char *expression; /* The current expression */
static char *tp; /* token lexical position */
static char *lasttp; /* pointer to last token position */
static int curtok; /* the current token */
static int lasttok; /* the previous token */
static int assigntok; /* the OP in OP= */
static char *tokstr; /* current token string */
static intmax_t tokval; /* current token value */
static int noeval; /* set to 1 if no assignment to be done */
static procenv_t evalbuf;
/* set to 1 if the expression has already been run through word expansion */
static int already_expanded;
static struct lvalue curlval = {0, 0, 0, -1};
static struct lvalue lastlval = {0, 0, 0, -1};
static int _is_arithop PARAMS((int));
static void readtok PARAMS((void)); /* lexical analyzer */
static void init_lvalue PARAMS((struct lvalue *));
static struct lvalue *alloc_lvalue PARAMS((void));
static void free_lvalue PARAMS((struct lvalue *));
static intmax_t expr_streval PARAMS((char *, int, struct lvalue *));
static intmax_t strlong PARAMS((char *));
static void evalerror PARAMS((const char *));
static void pushexp PARAMS((void));
static void popexp PARAMS((void));
static void expr_unwind PARAMS((void));
static void expr_bind_variable PARAMS((char *, char *));
#if defined (ARRAY_VARS)
static void expr_bind_array_element PARAMS((char *, arrayind_t, char *));
#endif
static intmax_t subexpr PARAMS((char *));
static intmax_t expcomma PARAMS((void));
static intmax_t expassign PARAMS((void));
static intmax_t expcond PARAMS((void));
static intmax_t explor PARAMS((void));
static intmax_t expland PARAMS((void));
static intmax_t expbor PARAMS((void));
static intmax_t expbxor PARAMS((void));
static intmax_t expband PARAMS((void));
static intmax_t exp5 PARAMS((void));
static intmax_t exp4 PARAMS((void));
static intmax_t expshift PARAMS((void));
static intmax_t exp3 PARAMS((void));
static intmax_t expmuldiv PARAMS((void));
static intmax_t exppower PARAMS((void));
static intmax_t exp1 PARAMS((void));
static intmax_t exp0 PARAMS((void));
/* Global var which contains the stack of expression contexts. */
static EXPR_CONTEXT **expr_stack;
static int expr_depth; /* Location in the stack. */
static int expr_stack_size; /* Number of slots already allocated. */
#if defined (ARRAY_VARS)
extern const char * const bash_badsub_errmsg;
#endif
#define SAVETOK(X) \
do { \
(X)->curtok = curtok; \
(X)->lasttok = lasttok; \
(X)->tp = tp; \
(X)->lasttp = lasttp; \
(X)->tokval = tokval; \
(X)->tokstr = tokstr; \
(X)->noeval = noeval; \
(X)->lval = curlval; \
} while (0)
#define RESTORETOK(X) \
do { \
curtok = (X)->curtok; \
lasttok = (X)->lasttok; \
tp = (X)->tp; \
lasttp = (X)->lasttp; \
tokval = (X)->tokval; \
tokstr = (X)->tokstr; \
noeval = (X)->noeval; \
curlval = (X)->lval; \
} while (0)
/* Push and save away the contents of the globals describing the
current expression context. */
static void
pushexp ()
{
EXPR_CONTEXT *context;
if (expr_depth >= MAX_EXPR_RECURSION_LEVEL)
evalerror (_("expression recursion level exceeded"));
if (expr_depth >= expr_stack_size)
{
expr_stack_size += EXPR_STACK_GROW_SIZE;
expr_stack = (EXPR_CONTEXT **)xrealloc (expr_stack, expr_stack_size * sizeof (EXPR_CONTEXT *));
}
context = (EXPR_CONTEXT *)xmalloc (sizeof (EXPR_CONTEXT));
context->expression = expression;
SAVETOK(context);
expr_stack[expr_depth++] = context;
}
/* Pop the the contents of the expression context stack into the
globals describing the current expression context. */
static void
popexp ()
{
EXPR_CONTEXT *context;
if (expr_depth <= 0)
{
/* See the comment at the top of evalexp() for an explanation of why
this is done. */
expression = lasttp = 0;
evalerror (_("recursion stack underflow"));
}
context = expr_stack[--expr_depth];
expression = context->expression;
RESTORETOK (context);
free (context);
}
static void
expr_unwind ()
{
while (--expr_depth > 0)
{
if (expr_stack[expr_depth]->tokstr)
free (expr_stack[expr_depth]->tokstr);
if (expr_stack[expr_depth]->expression)
free (expr_stack[expr_depth]->expression);
free (expr_stack[expr_depth]);
}
if (expr_depth == 0)
free (expr_stack[expr_depth]); /* free the allocated EXPR_CONTEXT */
noeval = 0; /* XXX */
}
static void
expr_bind_variable (lhs, rhs)
char *lhs, *rhs;
{
SHELL_VAR *v;
int aflags;
if (lhs == 0 || *lhs == 0)
return; /* XXX */
#if defined (ARRAY_VARS)
aflags = (assoc_expand_once && already_expanded) ? ASS_NOEXPAND : 0;
#else
aflags = 0;
#endif
v = bind_int_variable (lhs, rhs, aflags);
if (v && (readonly_p (v) || noassign_p (v)))
sh_longjmp (evalbuf, 1); /* variable assignment error */
stupidly_hack_special_variables (lhs);
}
#if defined (ARRAY_VARS)
/* This is similar to the logic in arrayfunc.c:valid_array_subscript when
you pass VA_NOEXPAND. */
static int
expr_skipsubscript (vp, cp)
char *vp, *cp;
{
int flags, isassoc;
SHELL_VAR *entry;
isassoc = 0;
entry = 0;
if (assoc_expand_once & already_expanded)
{
*cp = '\0';
isassoc = legal_identifier (vp) && (entry = find_variable (vp)) && assoc_p (entry);
*cp = '['; /* ] */
}
flags = (isassoc && assoc_expand_once && already_expanded) ? VA_NOEXPAND : 0;
return (skipsubscript (cp, 0, flags));
}
/* Rewrite tok, which is of the form vname[expression], to vname[ind], where
IND is the already-calculated value of expression. */
static void
expr_bind_array_element (tok, ind, rhs)
char *tok;
arrayind_t ind;
char *rhs;
{
char *lhs, *vname;
size_t llen;
char ibuf[INT_STRLEN_BOUND (arrayind_t) + 1], *istr;
istr = fmtumax (ind, 10, ibuf, sizeof (ibuf), 0);
vname = array_variable_name (tok, 0, (char **)NULL, (int *)NULL);
llen = strlen (vname) + sizeof (ibuf) + 3;
lhs = xmalloc (llen);
sprintf (lhs, "%s[%s]", vname, istr); /* XXX */
/*itrace("expr_bind_array_element: %s=%s", lhs, rhs);*/
expr_bind_variable (lhs, rhs);
free (vname);
free (lhs);
}
#endif /* ARRAY_VARS */
/* Evaluate EXPR, and return the arithmetic result. If VALIDP is
non-null, a zero is stored into the location to which it points
if the expression is invalid, non-zero otherwise. If a non-zero
value is returned in *VALIDP, the return value of evalexp() may
be used.
The `while' loop after the longjmp is caught relies on the above
implementation of pushexp and popexp leaving in expr_stack[0] the
values that the variables had when the program started. That is,
the first things saved are the initial values of the variables that
were assigned at program startup or by the compiler. Therefore, it is
safe to let the loop terminate when expr_depth == 0, without freeing up
any of the expr_depth[0] stuff. */
intmax_t
evalexp (expr, flags, validp)
char *expr;
int flags;
int *validp;
{
intmax_t val;
int c;
procenv_t oevalbuf;
val = 0;
noeval = 0;
already_expanded = (flags&EXP_EXPANDED);
FASTCOPY (evalbuf, oevalbuf, sizeof (evalbuf));
c = setjmp_nosigs (evalbuf);
if (c)
{
FREE (tokstr);
FREE (expression);
tokstr = expression = (char *)NULL;
expr_unwind ();
expr_depth = 0; /* XXX - make sure */
/* We copy in case we've called evalexp recursively */
FASTCOPY (oevalbuf, evalbuf, sizeof (evalbuf));
if (validp)
*validp = 0;
return (0);
}
val = subexpr (expr);
if (validp)
*validp = 1;
FASTCOPY (oevalbuf, evalbuf, sizeof (evalbuf));
return (val);
}
static intmax_t
subexpr (expr)
char *expr;
{
intmax_t val;
char *p;
for (p = expr; p && *p && cr_whitespace (*p); p++)
;
if (p == NULL || *p == '\0')
return (0);
pushexp ();
expression = savestring (expr);
tp = expression;
curtok = lasttok = 0;
tokstr = (char *)NULL;
tokval = 0;
init_lvalue (&curlval);
lastlval = curlval;
readtok ();
val = EXP_HIGHEST ();
if (curtok != 0)
evalerror (_("syntax error in expression"));
FREE (tokstr);
FREE (expression);
popexp ();
return val;
}
static intmax_t
expcomma ()
{
register intmax_t value;
value = expassign ();
while (curtok == COMMA)
{
readtok ();
value = expassign ();
}
return value;
}
static intmax_t
expassign ()
{
register intmax_t value;
char *lhs, *rhs;
arrayind_t lind;
#if defined (HAVE_IMAXDIV)
imaxdiv_t idiv;
#endif
value = expcond ();
if (curtok == EQ || curtok == OP_ASSIGN)
{
int special, op;
intmax_t lvalue;
special = curtok == OP_ASSIGN;
if (lasttok != STR)
evalerror (_("attempted assignment to non-variable"));
if (special)
{
op = assigntok; /* a OP= b */
lvalue = value;
}
if (tokstr == 0)
evalerror (_("syntax error in variable assignment"));
/* XXX - watch out for pointer aliasing issues here */
lhs = savestring (tokstr);
/* save ind in case rhs is string var and evaluation overwrites it */
lind = curlval.ind;
readtok ();
value = expassign ();
if (special)
{
if ((op == DIV || op == MOD) && value == 0)
{
if (noeval == 0)
evalerror (_("division by 0"));
else
value = 1;
}
switch (op)
{
case MUL:
/* Handle INTMAX_MIN and INTMAX_MAX * -1 specially here? */
lvalue *= value;
break;
case DIV:
case MOD:
if (lvalue == INTMAX_MIN && value == -1)
lvalue = (op == DIV) ? INTMAX_MIN : 0;
else
#if HAVE_IMAXDIV
{
idiv = imaxdiv (lvalue, value);
lvalue = (op == DIV) ? idiv.quot : idiv.rem;
}
#else
lvalue = (op == DIV) ? lvalue / value : lvalue % value;
#endif
break;
case PLUS:
lvalue += value;
break;
case MINUS:
lvalue -= value;
break;
case LSH:
lvalue <<= value;
break;
case RSH:
lvalue >>= value;
break;
case BAND:
lvalue &= value;
break;
case BOR:
lvalue |= value;
break;
case BXOR:
lvalue ^= value;
break;
default:
free (lhs);
evalerror (_("bug: bad expassign token"));
break;
}
value = lvalue;
}
rhs = itos (value);
if (noeval == 0)
{
#if defined (ARRAY_VARS)
if (lind != -1)
expr_bind_array_element (lhs, lind, rhs);
else
#endif
expr_bind_variable (lhs, rhs);
}
if (curlval.tokstr && curlval.tokstr == tokstr)
init_lvalue (&curlval);
free (rhs);
free (lhs);
FREE (tokstr);
tokstr = (char *)NULL; /* For freeing on errors. */
}
return (value);
}
/* Conditional expression (expr?expr:expr) */
static intmax_t
expcond ()
{
intmax_t cval, val1, val2, rval;
int set_noeval;
set_noeval = 0;
rval = cval = explor ();
if (curtok == QUES) /* found conditional expr */
{
if (cval == 0)
{
set_noeval = 1;
noeval++;
}
readtok ();
if (curtok == 0 || curtok == COL)
evalerror (_("expression expected"));
val1 = EXP_HIGHEST ();
if (set_noeval)
noeval--;
if (curtok != COL)
evalerror (_("`:' expected for conditional expression"));
set_noeval = 0;
if (cval)
{
set_noeval = 1;
noeval++;
}
readtok ();
if (curtok == 0)
evalerror (_("expression expected"));
val2 = expcond ();
if (set_noeval)
noeval--;
rval = cval ? val1 : val2;
lasttok = COND;
}
return rval;
}
/* Logical OR. */
static intmax_t
explor ()
{
register intmax_t val1, val2;
int set_noeval;
val1 = expland ();
while (curtok == LOR)
{
set_noeval = 0;
if (val1 != 0)
{
noeval++;
set_noeval = 1;
}
readtok ();
val2 = expland ();
if (set_noeval)
noeval--;
val1 = val1 || val2;
lasttok = LOR;
}
return (val1);
}
/* Logical AND. */
static intmax_t
expland ()
{
register intmax_t val1, val2;
int set_noeval;
val1 = expbor ();
while (curtok == LAND)
{
set_noeval = 0;
if (val1 == 0)
{
set_noeval = 1;
noeval++;
}
readtok ();
val2 = expbor ();
if (set_noeval)
noeval--;
val1 = val1 && val2;
lasttok = LAND;
}
return (val1);
}
/* Bitwise OR. */
static intmax_t
expbor ()
{
register intmax_t val1, val2;
val1 = expbxor ();
while (curtok == BOR)
{
readtok ();
val2 = expbxor ();
val1 = val1 | val2;
lasttok = NUM;
}
return (val1);
}
/* Bitwise XOR. */
static intmax_t
expbxor ()
{
register intmax_t val1, val2;
val1 = expband ();
while (curtok == BXOR)
{
readtok ();
val2 = expband ();
val1 = val1 ^ val2;
lasttok = NUM;
}
return (val1);
}
/* Bitwise AND. */
static intmax_t
expband ()
{
register intmax_t val1, val2;
val1 = exp5 ();
while (curtok == BAND)
{
readtok ();
val2 = exp5 ();
val1 = val1 & val2;
lasttok = NUM;
}
return (val1);
}
static intmax_t
exp5 ()
{
register intmax_t val1, val2;
val1 = exp4 ();
while ((curtok == EQEQ) || (curtok == NEQ))
{
int op = curtok;
readtok ();
val2 = exp4 ();
if (op == EQEQ)
val1 = (val1 == val2);
else if (op == NEQ)
val1 = (val1 != val2);
lasttok = NUM;
}
return (val1);
}
static intmax_t
exp4 ()
{
register intmax_t val1, val2;
val1 = expshift ();
while ((curtok == LEQ) ||
(curtok == GEQ) ||
(curtok == LT) ||
(curtok == GT))
{
int op = curtok;
readtok ();
val2 = expshift ();
if (op == LEQ)
val1 = val1 <= val2;
else if (op == GEQ)
val1 = val1 >= val2;
else if (op == LT)
val1 = val1 < val2;
else /* (op == GT) */
val1 = val1 > val2;
lasttok = NUM;
}
return (val1);
}
/* Left and right shifts. */
static intmax_t
expshift ()
{
register intmax_t val1, val2;
val1 = exp3 ();
while ((curtok == LSH) || (curtok == RSH))
{
int op = curtok;
readtok ();
val2 = exp3 ();
if (op == LSH)
val1 = val1 << val2;
else
val1 = val1 >> val2;
lasttok = NUM;
}
return (val1);
}
static intmax_t
exp3 ()
{
register intmax_t val1, val2;
val1 = expmuldiv ();
while ((curtok == PLUS) || (curtok == MINUS))
{
int op = curtok;
readtok ();
val2 = expmuldiv ();
if (op == PLUS)
val1 += val2;
else if (op == MINUS)
val1 -= val2;
lasttok = NUM;
}
return (val1);
}
static intmax_t
expmuldiv ()
{
register intmax_t val1, val2;
#if defined (HAVE_IMAXDIV)
imaxdiv_t idiv;
#endif
val1 = exppower ();
while ((curtok == MUL) ||
(curtok == DIV) ||
(curtok == MOD))
{
int op = curtok;
char *stp, *sltp;
stp = tp;
readtok ();
val2 = exppower ();
/* Handle division by 0 and twos-complement arithmetic overflow */
if (((op == DIV) || (op == MOD)) && (val2 == 0))
{
if (noeval == 0)
{
sltp = lasttp;
lasttp = stp;
while (lasttp && *lasttp && whitespace (*lasttp))
lasttp++;
evalerror (_("division by 0"));
lasttp = sltp;
}
else
val2 = 1;
}
else if (op == MOD && val1 == INTMAX_MIN && val2 == -1)
{
val1 = 0;
continue;
}
else if (op == DIV && val1 == INTMAX_MIN && val2 == -1)
val2 = 1;
if (op == MUL)
val1 *= val2;
else if (op == DIV || op == MOD)
#if defined (HAVE_IMAXDIV)
{
idiv = imaxdiv (val1, val2);
val1 = (op == DIV) ? idiv.quot : idiv.rem;
}
#else
val1 = (op == DIV) ? val1 / val2 : val1 % val2;
#endif
lasttok = NUM;
}
return (val1);
}
static intmax_t
ipow (base, exp)
intmax_t base, exp;
{
intmax_t result;
result = 1;
while (exp)
{
if (exp & 1)
result *= base;
exp >>= 1;
base *= base;
}
return result;
}
static intmax_t
exppower ()
{
register intmax_t val1, val2, c;
val1 = exp1 ();
while (curtok == POWER)
{
readtok ();
val2 = exppower (); /* exponentiation is right-associative */
lasttok = NUM;
if (val2 == 0)
return (1);
if (val2 < 0)
evalerror (_("exponent less than 0"));
val1 = ipow (val1, val2);
}
return (val1);
}
static intmax_t
exp1 ()
{
register intmax_t val;
if (curtok == NOT)
{
readtok ();
val = !exp1 ();
lasttok = NUM;
}
else if (curtok == BNOT)
{
readtok ();
val = ~exp1 ();
lasttok = NUM;
}
else if (curtok == MINUS)
{
readtok ();
val = - exp1 ();
lasttok = NUM;
}