4.4BSD/usr/src/contrib/emacs-18.57/cpp/cexp.y
/* Parse C expressions for CCCP.
Copyright (C) 1986 Free Software Foundation.
NO WARRANTY
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Adapted from expread.y of GDB by Paul Rubin, July 1986.
/* Parse a C expression from text in a string */
%{
#include <setjmp.h>
/* #define YYDEBUG 1 */
static int yylex ();
static yyerror ();
int expression_value;
static jmp_buf parse_return_error;
/* some external tables of character types */
extern unsigned char is_idstart[], is_idchar[];
%}
%union {
long lval;
int voidval;
char *sval;
}
%type <lval> exp exp1 start
%token <lval> INT CHAR
%token <sval> NAME
%token <lval> ERROR
%left ','
%left OR
%left AND
%left '|'
%left '^'
%left '&'
%left EQUAL NOTEQUAL
%left '<' '>' LEQ GEQ
%left LSH RSH
%left '+' '-'
%left '*' '/' '%'
%right UNARY
%%
start : exp1
{ expression_value = $1; }
;
/* Expressions, including the comma operator. */
exp1 : exp
| exp1 ',' exp
{ $$ = $3; }
;
/* Expressions, not including the comma operator. */
exp : '-' exp %prec UNARY
{ $$ = - $2; }
| '!' exp %prec UNARY
{ $$ = ! $2; }
| '~' exp %prec UNARY
{ $$ = ~ $2; }
| '(' exp1 ')'
{ $$ = $2; }
;
/* Binary operators in order of decreasing precedence. */
exp : exp '*' exp
{ $$ = $1 * $3; }
| exp '/' exp
{ $$ = $1 / $3; }
| exp '%' exp
{ $$ = $1 % $3; }
| exp '+' exp
{ $$ = $1 + $3; }
| exp '-' exp
{ $$ = $1 - $3; }
| exp LSH exp
{ $$ = $1 << $3; }
| exp RSH exp
{ $$ = $1 >> $3; }
| exp EQUAL exp
{ $$ = ($1 == $3); }
| exp NOTEQUAL exp
{ $$ = ($1 != $3); }
| exp LEQ exp
{ $$ = ($1 <= $3); }
| exp GEQ exp
{ $$ = ($1 >= $3); }
| exp '<' exp
{ $$ = ($1 < $3); }
| exp '>' exp
{ $$ = ($1 > $3); }
| exp '&' exp
{ $$ = ($1 & $3); }
| exp '^' exp
{ $$ = ($1 ^ $3); }
| exp '|' exp
{ $$ = ($1 | $3); }
| exp AND exp
{ $$ = ($1 && $3); }
| exp OR exp
{ $$ = ($1 || $3); }
| exp '?' exp ':' exp
{ $$ = $1 ? $3 : $5; }
| INT
{ $$ = yylval.lval; }
| CHAR
{ $$ = yylval.lval; }
| NAME
{ $$ = 0; }
;
%%
/* During parsing of a C expression, the pointer to the next character
is in this variable. */
static char *lexptr;
/* Take care of parsing a number (anything that starts with a digit).
Set yylval and return the token type; update lexptr.
LEN is the number of characters in it. */
/* maybe needs to actually deal with floating point numbers */
static int
parse_number (olen)
int olen;
{
register char *p = lexptr;
register long n = 0;
register int c;
register int base = 10;
register len = olen;
char *err_copy;
extern double atof ();
for (c = 0; c < len; c++)
if (p[c] == '.') {
/* It's a float since it contains a point. */
yyerror ("floating point numbers not allowed in #if expressions");
return ERROR;
/* ****************
yylval.dval = atof (p);
lexptr += len;
return FLOAT;
**************** */
}
if (len >= 3 && (!strncmp (p, "0x", 2) || !strncmp (p, "0X", 2))) {
p += 2;
base = 16;
len -= 2;
}
else if (*p == '0')
base = 8;
while (len-- > 0) {
c = *p++;
n *= base;
if (c >= '0' && c <= '9')
n += c - '0';
else {
if (c >= 'A' && c <= 'Z') c += 'a' - 'A';
if (base == 16 && c >= 'a' && c <= 'f')
n += c - 'a' + 10;
else if (len == 0 && c == 'l')
;
else {
yyerror ("Invalid number in #if expression");
return ERROR;
}
}
}
lexptr = p;
yylval.lval = n;
return INT;
}
struct token {
char *operator;
int token;
};
#define NULL 0
static struct token tokentab2[] = {
{"&&", AND},
{"||", OR},
{"<<", LSH},
{">>", RSH},
{"==", EQUAL},
{"!=", NOTEQUAL},
{"<=", LEQ},
{">=", GEQ},
{NULL, ERROR}
};
/* Read one token, getting characters through lexptr. */
static int
yylex ()
{
register int c;
register int namelen;
register char *tokstart;
register struct token *toktab;
retry:
tokstart = lexptr;
c = *tokstart;
/* See if it is a special token of length 2. */
for (toktab = tokentab2; toktab->operator != NULL; toktab++)
if (c == *toktab->operator && tokstart[1] == toktab->operator[1]) {
lexptr += 2;
return toktab->token;
}
switch (c) {
case 0:
return 0;
case ' ':
case '\t':
case '\n':
lexptr++;
goto retry;
case '\'':
lexptr++;
c = *lexptr++;
if (c == '\\')
c = parse_escape (&lexptr);
yylval.lval = c;
c = *lexptr++;
if (c != '\'') {
yyerror ("Invalid character constant in #if");
return ERROR;
}
return CHAR;
case '/': /* possible comment */
if (*lexptr != '*')
return c;
for (;;) {
while (*lexptr != '\0') {
if (*lexptr++ == '*' && *lexptr == '/') {
lexptr++;
goto retry;
}
}
}
/* some of these chars are invalid in constant expressions;
maybe do something about them later */
case '+':
case '-':
case '*':
case '%':
case '|':
case '&':
case '^':
case '~':
case '!':
case '@':
case '<':
case '>':
case '(':
case ')':
case '[':
case ']':
case '.':
case '?':
case ':':
case '=':
case '{':
case '}':
case ',':
lexptr++;
return c;
case '"':
yyerror ("double quoted strings not allowed in #if expressions");
return ERROR;
}
if (c >= '0' && c <= '9') {
/* It's a number */
for (namelen = 0;
c = tokstart[namelen], is_idchar[c] || c == '.';
namelen++)
;
return parse_number (namelen);
}
if (!is_idstart[c]) {
yyerror ("Invalid token in expression");
return ERROR;
}
/* It is a name. See how long it is. */
for (namelen = 0; is_idchar[tokstart[namelen]]; namelen++)
;
lexptr += namelen;
return NAME;
}
/* Parse a C escape sequence. STRING_PTR points to a variable
containing a pointer to the string to parse. That pointer
is updated past the characters we use. The value of the
escape sequence is returned.
A negative value means the sequence \ newline was seen,
which is supposed to be equivalent to nothing at all.
If \ is followed by a null character, we return a negative
value and leave the string pointer pointing at the null character.
If \ is followed by 000, we return 0 and leave the string pointer
after the zeros. A value of 0 does not mean end of string. */
static int
parse_escape (string_ptr)
char **string_ptr;
{
register int c = *(*string_ptr)++;
switch (c)
{
case 'a':
return '\a';
case 'b':
return '\b';
case 'e':
return 033;
case 'f':
return '\f';
case 'n':
return '\n';
case 'r':
return '\r';
case 't':
return '\t';
case 'v':
return '\v';
case '\n':
return -2;
case 0:
(*string_ptr)--;
return 0;
case '^':
c = *(*string_ptr)++;
if (c == '\\')
c = parse_escape (string_ptr);
if (c == '?')
return 0177;
return (c & 0200) | (c & 037);
case '0':
case '1':
case '2':
case '3':
case '4':
case '5':
case '6':
case '7':
{
register int i = c - '0';
register int count = 0;
while (++count < 3)
{
if ((c = *(*string_ptr)++) >= '0' && c <= '7')
{
i *= 8;
i += c - '0';
}
else
{
(*string_ptr)--;
break;
}
}
return i;
}
default:
return c;
}
}
static
yyerror (s)
char *s;
{
error (s);
longjmp (parse_return_error, 1);
}
/* This page contains the entry point to this file. */
/* Parse STRING as an expression, and complain if this fails
to use up all of the contents of STRING. */
int
parse_c_expression (string)
char *string;
{
lexptr = string;
if (lexptr == 0 || *lexptr == 0) {
error ("empty #if expression");
return 0; /* don't include the #if group */
}
/* if there is some sort of scanning error, just return 0 and assume
the parsing routine has printed an error message somewhere.
there is surely a better thing to do than this. */
if (setjmp(parse_return_error))
return 0;
if (yyparse ())
return 0; /* actually this is never reached
the way things stand. */
if (*lexptr)
error ("Junk after end of expression.");
return expression_value; /* set by yyparse() */
}
#ifdef TEST_EXP_READER
/* main program, for testing purposes. */
main()
{
int n;
char buf[1024];
extern int yydebug;
/*
yydebug = 1;
*/
initialize_random_junk ();
for (;;) {
printf("enter expression: ");
n = 0;
while ((buf[n] = getchar()) != '\n')
n++;
buf[n] = '\0';
printf("parser returned %d\n", parse_c_expression(buf));
}
}
/* table to tell if char can be part of a C identifier. */
char is_idchar[256];
/* table to tell if char can be first char of a c identifier. */
char is_idstart[256];
/* table to tell if c is horizontal space. isspace() thinks that
newline is space; this is not a good idea for this program. */
char is_hor_space[256];
/*
* initialize random junk in the hash table and maybe other places
*/
initialize_random_junk()
{
register int i;
/*
* Set up is_idchar and is_idstart tables. These should be
* faster than saying (is_alpha(c) || c == '_'), etc.
* Must do set up these things before calling any routines tthat
* refer to them.
*/
for (i = 'a'; i <= 'z'; i++) {
++is_idchar[i - 'a' + 'A'];
++is_idchar[i];
++is_idstart[i - 'a' + 'A'];
++is_idstart[i];
}
for (i = '0'; i <= '9'; i++)
++is_idchar[i];
++is_idchar['_'];
++is_idstart['_'];
/* horizontal space table */
++is_hor_space[' '];
++is_hor_space['\t'];
}
error (msg)
{
printf("error: %s\n", msg);
}
#endif