xref: /src/usr.bin/make/cond.c

/*	$NetBSD: cond.c,v 1.228 2020/12/20 13:03:48 rillig Exp $	*/

/*
 * Copyright (c) 1988, 1989, 1990 The Regents of the University of California.
 * All rights reserved.
 *
 * This code is derived from software contributed to Berkeley by
 * Adam de Boor.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. Neither the name of the University nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 */

/*
 * Copyright (c) 1988, 1989 by Adam de Boor
 * Copyright (c) 1989 by Berkeley Softworks
 * All rights reserved.
 *
 * This code is derived from software contributed to Berkeley by
 * Adam de Boor.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. All advertising materials mentioning features or use of this software
 *    must display the following acknowledgement:
 *	This product includes software developed by the University of
 *	California, Berkeley and its contributors.
 * 4. Neither the name of the University nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 */

/* Handling of conditionals in a makefile.
 *
 * Interface:
 *	Cond_EvalLine   Evaluate the conditional directive, such as
 *			'.if <cond>', '.elifnmake <cond>', '.else', '.endif'.
 *
 *	Cond_EvalCondition
 *			Evaluate the conditional, which is either the argument
 *			of one of the .if directives or the condition in a
 *			':?then:else' variable modifier.
 *
 *	Cond_save_depth
 *	Cond_restore_depth
 *			Save and restore the nesting of the conditions, at
 *			the start and end of including another makefile, to
 *			ensure that in each makefile the conditional
 *			directives are well-balanced.
 */

#include <errno.h>

#include "make.h"
#include "dir.h"

/*	"@(#)cond.c	8.2 (Berkeley) 1/2/94"	*/
MAKE_RCSID("$NetBSD: cond.c,v 1.228 2020/12/20 13:03:48 rillig Exp $");

/*
 * The parsing of conditional expressions is based on this grammar:
 *	E -> F || E
 *	E -> F
 *	F -> T && F
 *	F -> T
 *	T -> defined(variable)
 *	T -> make(target)
 *	T -> exists(file)
 *	T -> empty(varspec)
 *	T -> target(name)
 *	T -> commands(name)
 *	T -> symbol
 *	T -> $(varspec) op value
 *	T -> $(varspec) == "string"
 *	T -> $(varspec) != "string"
 *	T -> "string"
 *	T -> ( E )
 *	T -> ! T
 *	op -> == | != | > | < | >= | <=
 *
 * 'symbol' is some other symbol to which the default function is applied.
 *
 * The tokens are scanned by CondToken, which returns:
 *	TOK_AND		for '&' or '&&'
 *	TOK_OR		for '|' or '||'
 *	TOK_NOT		for '!'
 *	TOK_LPAREN	for '('
 *	TOK_RPAREN	for ')'
 * Other terminal symbols are evaluated using either the default function or
 * the function given in the terminal, they return either TOK_TRUE or
 * TOK_FALSE.
 *
 * TOK_FALSE is 0 and TOK_TRUE 1 so we can directly assign C comparisons.
 *
 * All non-terminal functions (CondParser_Expr, CondParser_Factor and
 * CondParser_Term) return either TOK_FALSE, TOK_TRUE, or TOK_ERROR on error.
 */
typedef enum Token {
	TOK_FALSE = 0, TOK_TRUE = 1, TOK_AND, TOK_OR, TOK_NOT,
	TOK_LPAREN, TOK_RPAREN, TOK_EOF, TOK_NONE, TOK_ERROR
} Token;

typedef struct CondParser {
	const struct If *if_info; /* Info for current statement */
	const char *p;		/* The remaining condition to parse */
	Token curr;		/* Single push-back token used in parsing */

	/*
	 * Whether an error message has already been printed for this
	 * condition. The first available error message is usually the most
	 * specific one, therefore it makes sense to suppress the standard
	 * "Malformed conditional" message.
	 */
	Boolean printedError;
} CondParser;

static Token CondParser_Expr(CondParser *par, Boolean);

static unsigned int cond_depth = 0;	/* current .if nesting level */
static unsigned int cond_min_depth = 0;	/* depth at makefile open */

/*
 * Indicate when we should be strict about lhs of comparisons.
 * In strict mode, the lhs must be a variable expression or a string literal
 * in quotes. In non-strict mode it may also be an unquoted string literal.
 *
 * TRUE when CondEvalExpression is called from Cond_EvalLine (.if etc)
 * FALSE when CondEvalExpression is called from ApplyModifier_IfElse
 * since lhs is already expanded, and at that point we cannot tell if
 * it was a variable reference or not.
 */
static Boolean lhsStrict;

static int
is_token(const char *str, const char *tok, size_t len)
{
	return strncmp(str, tok, len) == 0 && !ch_isalpha(str[len]);
}

static Token
ToToken(Boolean cond)
{
	return cond ? TOK_TRUE : TOK_FALSE;
}

/* Push back the most recent token read. We only need one level of this. */
static void
CondParser_PushBack(CondParser *par, Token t)
{
	assert(par->curr == TOK_NONE);
	assert(t != TOK_NONE);

	par->curr = t;
}

static void
CondParser_SkipWhitespace(CondParser *par)
{
	cpp_skip_whitespace(&par->p);
}

/* Parse the argument of a built-in function.
 *
 * Arguments:
 *	*pp initially points at the '(',
 *	upon successful return it points right after the ')'.
 *
 *	*out_arg receives the argument as string.
 *
 *	func says whether the argument belongs to an actual function, or
 *	whether the parsed argument is passed to the default function.
 *
 * Return the length of the argument, or 0 on error. */
static size_t
ParseFuncArg(const char **pp, Boolean doEval, const char *func,
	     char **out_arg)
{
	const char *p = *pp;
	Buffer argBuf;
	int paren_depth;
	size_t argLen;

	if (func != NULL)
		p++;		/* Skip opening '(' - verified by caller */

	if (*p == '\0') {
		*out_arg = NULL; /* Missing closing parenthesis: */
		return 0;	/* .if defined( */
	}

	cpp_skip_hspace(&p);

	Buf_InitSize(&argBuf, 16);

	paren_depth = 0;
	for (;;) {
		char ch = *p;
		if (ch == '\0' || ch == ' ' || ch == '\t')
			break;
		if ((ch == '&' || ch == '|') && paren_depth == 0)
			break;
		if (*p == '$') {
			/*
			 * Parse the variable expression and install it as
			 * part of the argument if it's valid. We tell
			 * Var_Parse to complain on an undefined variable,
			 * (XXX: but Var_Parse ignores that request)
			 * so we don't need to do it. Nor do we return an
			 * error, though perhaps we should.
			 */
			void *nestedVal_freeIt;
			VarEvalFlags eflags = doEval
			    ? VARE_WANTRES | VARE_UNDEFERR
			    : VARE_NONE;
			const char *nestedVal;
			(void)Var_Parse(&p, VAR_CMDLINE, eflags,
					&nestedVal, &nestedVal_freeIt);
			/* TODO: handle errors */
			Buf_AddStr(&argBuf, nestedVal);
			free(nestedVal_freeIt);
			continue;
		}
		if (ch == '(')
			paren_depth++;
		else if (ch == ')' && --paren_depth < 0)
			break;
		Buf_AddByte(&argBuf, *p);
		p++;
	}

	*out_arg = Buf_GetAll(&argBuf, &argLen);
	Buf_Destroy(&argBuf, FALSE);

	cpp_skip_hspace(&p);

	if (func != NULL && *p++ != ')') {
		Parse_Error(PARSE_WARNING,
			    "Missing closing parenthesis for %s()",
			    func);
		/* The PARSE_FATAL follows in CondEvalExpression. */
		return 0;
	}

	*pp = p;
	return argLen;
}

/* Test whether the given variable is defined. */
static Boolean
FuncDefined(size_t argLen MAKE_ATTR_UNUSED, const char *arg)
{
	void *freeIt;
	Boolean result = Var_Value(arg, VAR_CMDLINE, &freeIt) != NULL;
	bmake_free(freeIt);
	return result;
}

/* See if the given target is being made. */
static Boolean
FuncMake(size_t argLen MAKE_ATTR_UNUSED, const char *arg)
{
	StringListNode *ln;

	for (ln = opts.create.first; ln != NULL; ln = ln->next)
		if (Str_Match(ln->datum, arg))
			return TRUE;
	return FALSE;
}

/* See if the given file exists. */
static Boolean
FuncExists(size_t argLen MAKE_ATTR_UNUSED, const char *arg)
{
	Boolean result;
	char *path;

	path = Dir_FindFile(arg, &dirSearchPath);
	DEBUG2(COND, "exists(%s) result is \"%s\"\n",
	       arg, path != NULL ? path : "");
	result = path != NULL;
	free(path);
	return result;
}

/* See if the given node exists and is an actual target. */
static Boolean
FuncTarget(size_t argLen MAKE_ATTR_UNUSED, const char *arg)
{
	GNode *gn = Targ_FindNode(arg);
	return gn != NULL && GNode_IsTarget(gn);
}

/* See if the given node exists and is an actual target with commands
 * associated with it. */
static Boolean
FuncCommands(size_t argLen MAKE_ATTR_UNUSED, const char *arg)
{
	GNode *gn = Targ_FindNode(arg);
	return gn != NULL && GNode_IsTarget(gn) && !Lst_IsEmpty(&gn->commands);
}

/*
 * Convert the given number into a double.
 * We try a base 10 or 16 integer conversion first, if that fails
 * then we try a floating point conversion instead.
 *
 * Results:
 *	Returns TRUE if the conversion succeeded.
 *	Sets 'out_value' to the converted number.
 */
static Boolean
TryParseNumber(const char *str, double *out_value)
{
	char *end;
	unsigned long ul_val;
	double dbl_val;

	errno = 0;
	if (str[0] == '\0') {	/* XXX: why is an empty string a number? */
		*out_value = 0.0;
		return TRUE;
	}

	ul_val = strtoul(str, &end, str[1] == 'x' ? 16 : 10);
	if (*end == '\0' && errno != ERANGE) {
		*out_value = str[0] == '-' ? -(double)-ul_val : (double)ul_val;
		return TRUE;
	}

	if (*end != '\0' && *end != '.' && *end != 'e' && *end != 'E')
		return FALSE;	/* skip the expensive strtod call */
	dbl_val = strtod(str, &end);
	if (*end != '\0')
		return FALSE;

	*out_value = dbl_val;
	return TRUE;
}

static Boolean
is_separator(char ch)
{
	return ch == '\0' || ch_isspace(ch) || strchr("!=><)", ch) != NULL;
}

/*-
 * Parse a string from a variable reference or an optionally quoted
 * string.  This is called for the lhs and rhs of string comparisons.
 *
 * Results:
 *	Returns the string, absent any quotes, or NULL on error.
 *	Sets out_quoted if the string was quoted.
 *	Sets out_freeIt.
 */
/* coverity:[+alloc : arg-*4] */
static void
CondParser_String(CondParser *par, Boolean doEval, Boolean strictLHS,
		  FStr *out_str, Boolean *out_quoted)
{
	Buffer buf;
	FStr str;
	Boolean atStart;
	const char *nested_p;
	Boolean quoted;
	const char *start;
	VarEvalFlags eflags;
	VarParseResult parseResult;

	Buf_Init(&buf);
	str = FStr_InitRefer(NULL);
	*out_quoted = quoted = par->p[0] == '"';
	start = par->p;
	if (quoted)
		par->p++;

	while (par->p[0] != '\0' && str.str == NULL) {
		switch (par->p[0]) {
		case '\\':
			par->p++;
			if (par->p[0] != '\0') {
				Buf_AddByte(&buf, par->p[0]);
				par->p++;
			}
			continue;
		case '"':
			if (quoted) {
				par->p++;	/* skip the closing quote */
				goto got_str;
			}
			Buf_AddByte(&buf, par->p[0]); /* likely? */
			par->p++;
			continue;
		case ')':	/* see is_separator */
		case '!':
		case '=':
		case '>':
		case '<':
		case ' ':
		case '\t':
			if (!quoted)
				goto got_str;
			Buf_AddByte(&buf, par->p[0]);
			par->p++;
			continue;
		case '$':
			/* if we are in quotes, an undefined variable is ok */
			eflags =
			    doEval && !quoted ? VARE_WANTRES | VARE_UNDEFERR :
			    doEval ? VARE_WANTRES :
			    VARE_NONE;

			nested_p = par->p;
			atStart = nested_p == start;
			parseResult = Var_Parse(&nested_p, VAR_CMDLINE, eflags,
						&str.str, &str.freeIt);
			/* TODO: handle errors */
			if (str.str == var_Error) {
				if (parseResult & VPR_ANY_MSG)
					par->printedError = TRUE;
				/*
				 * XXX: Can there be any situation in which
				 * a returned var_Error requires freeIt?
				 */
				FStr_Done(&str);
				/*
				 * Even if !doEval, we still report syntax
				 * errors, which is what getting var_Error
				 * back with !doEval means.
				 */
				str = FStr_InitRefer(NULL);
				goto cleanup;
			}
			par->p = nested_p;

			/*
			 * If the '$' started the string literal (which means
			 * no quotes), and the variable expression is followed
			 * by a space, looks like a comparison operator or is
			 * the end of the expression, we are done.
			 */
			if (atStart && is_separator(par->p[0]))
				goto cleanup;

			Buf_AddStr(&buf, str.str);
			FStr_Done(&str);
			str = FStr_InitRefer(NULL); /* not finished yet */
			continue;
		default:
			if (strictLHS && !quoted && *start != '$' &&
			    !ch_isdigit(*start)) {
				/*
				 * The left-hand side must be quoted,
				 * a variable reference or a number.
				 */
				str = FStr_InitRefer(NULL);
				goto cleanup;
			}
			Buf_AddByte(&buf, par->p[0]);
			par->p++;
			continue;
		}
	}
got_str:
	str = FStr_InitOwn(Buf_GetAll(&buf, NULL));
cleanup:
	Buf_Destroy(&buf, FALSE);
	*out_str = str;
}

struct If {
	const char *form;	/* Form of if */
	size_t formlen;		/* Length of form */
	Boolean doNot;		/* TRUE if default function should be negated */
	/* The default function to apply on unquoted bare words. */
	Boolean (*defProc)(size_t, const char *);
};

/* The different forms of .if directives. */
static const struct If ifs[] = {
    { "def",   3, FALSE, FuncDefined },
    { "ndef",  4, TRUE,  FuncDefined },
    { "make",  4, FALSE, FuncMake },
    { "nmake", 5, TRUE,  FuncMake },
    { "",      0, FALSE, FuncDefined },
    { NULL,    0, FALSE, NULL }
};
enum {
	PLAIN_IF_INDEX = 4
};

static Boolean
If_Eval(const struct If *if_info, const char *arg, size_t arglen)
{
	Boolean res = if_info->defProc(arglen, arg);
	return if_info->doNot ? !res : res;
}

/* Evaluate a "comparison without operator", such as in ".if ${VAR}" or
 * ".if 0". */
static Boolean
EvalNotEmpty(CondParser *par, const char *value, Boolean quoted)
{
	double num;

	/* For .ifxxx "...", check for non-empty string. */
	if (quoted)
		return value[0] != '\0';

	/* For .ifxxx <number>, compare against zero */
	if (TryParseNumber(value, &num))
		return num != 0.0;

	/* For .if ${...}, check for non-empty string.  This is different from
	 * the evaluation function from that .if variant, which would test
	 * whether a variable of the given name were defined. */
	/* XXX: Whitespace should count as empty, just as in ParseEmptyArg. */
	if (par->if_info->form[0] == '\0')
		return value[0] != '\0';

	/* For the other variants of .ifxxx ${...}, use its default function. */
	return If_Eval(par->if_info, value, strlen(value));
}

/* Evaluate a numerical comparison, such as in ".if ${VAR} >= 9". */
static Token
EvalCompareNum(double lhs, const char *op, double rhs)
{
	DEBUG3(COND, "lhs = %f, rhs = %f, op = %.2s\n", lhs, rhs, op);

	switch (op[0]) {
	case '!':
		if (op[1] != '=') {
			Parse_Error(PARSE_WARNING, "Unknown operator");
			/* The PARSE_FATAL follows in CondEvalExpression. */
			return TOK_ERROR;
		}
		return ToToken(lhs != rhs);
	case '=':
		if (op[1] != '=') {
			Parse_Error(PARSE_WARNING, "Unknown operator");
			/* The PARSE_FATAL follows in CondEvalExpression. */
			return TOK_ERROR;
		}
		return ToToken(lhs == rhs);
	case '<':
		return ToToken(op[1] == '=' ? lhs <= rhs : lhs < rhs);
	case '>':
		return ToToken(op[1] == '=' ? lhs >= rhs : lhs > rhs);
	}
	return TOK_ERROR;
}

static Token
EvalCompareStr(const char *lhs, const char *op, const char *rhs)
{
	if (!((op[0] == '!' || op[0] == '=') && op[1] == '=')) {
		Parse_Error(PARSE_WARNING,
			    "String comparison operator "
			    "must be either == or !=");
		/* The PARSE_FATAL follows in CondEvalExpression. */
		return TOK_ERROR;
	}

	DEBUG3(COND, "lhs = \"%s\", rhs = \"%s\", op = %.2s\n", lhs, rhs, op);
	return ToToken((*op == '=') == (strcmp(lhs, rhs) == 0));
}

/* Evaluate a comparison, such as "${VAR} == 12345". */
static Token
EvalCompare(const char *lhs, Boolean lhsQuoted, const char *op,
	    const char *rhs, Boolean rhsQuoted)
{
	double left, right;

	if (!rhsQuoted && !lhsQuoted)
		if (TryParseNumber(lhs, &left) && TryParseNumber(rhs, &right))
			return EvalCompareNum(left, op, right);

	return EvalCompareStr(lhs, op, rhs);
}

/* Parse a comparison condition such as:
 *
 *	0
 *	${VAR:Mpattern}
 *	${VAR} == value
 *	${VAR:U0} < 12345
 */
static Token
CondParser_Comparison(CondParser *par, Boolean doEval)
{
	Token t = TOK_ERROR;
	FStr lhs, rhs;
	const char *op;
	Boolean lhsQuoted, rhsQuoted;

	/*
	 * Parse the variable spec and skip over it, saving its
	 * value in lhs.
	 */
	CondParser_String(par, doEval, lhsStrict, &lhs, &lhsQuoted);
	if (lhs.str == NULL)
		goto done_lhs;

	CondParser_SkipWhitespace(par);

	op = par->p;
	switch (par->p[0]) {
	case '!':
	case '=':
	case '<':
	case '>':
		if (par->p[1] == '=')
			par->p += 2;
		else
			par->p++;
		break;
	default:
		/* Unknown operator, compare against an empty string or 0. */
		t = ToToken(doEval && EvalNotEmpty(par, lhs.str, lhsQuoted));
		goto done_lhs;
	}

	CondParser_SkipWhitespace(par);

	if (par->p[0] == '\0') {
		Parse_Error(PARSE_WARNING,
			    "Missing right-hand-side of operator");
		/* The PARSE_FATAL follows in CondEvalExpression. */
		goto done_lhs;
	}

	CondParser_String(par, doEval, FALSE, &rhs, &rhsQuoted);
	if (rhs.str == NULL)
		goto done_rhs;

	if (!doEval) {
		t = TOK_FALSE;
		goto done_rhs;
	}

	t = EvalCompare(lhs.str, lhsQuoted, op, rhs.str, rhsQuoted);

done_rhs:
	FStr_Done(&rhs);
done_lhs:
	FStr_Done(&lhs);
	return t;
}

/* The argument to empty() is a variable name, optionally followed by
 * variable modifiers. */
static size_t
ParseEmptyArg(const char **pp, Boolean doEval,
	      const char *func MAKE_ATTR_UNUSED, char **out_arg)
{
	void *val_freeIt;
	const char *val;
	size_t magic_res;

	/* We do all the work here and return the result as the length */
	*out_arg = NULL;

	(*pp)--;		/* Make (*pp)[1] point to the '('. */
	(void)Var_Parse(pp, VAR_CMDLINE, doEval ? VARE_WANTRES : VARE_NONE,
			&val, &val_freeIt);
	/* TODO: handle errors */
	/* If successful, *pp points beyond the closing ')' now. */

	if (val == var_Error) {
		free(val_freeIt);
		return (size_t)-1;
	}

	/*
	 * A variable is empty when it just contains spaces...
	 * 4/15/92, christos
	 */
	cpp_skip_whitespace(&val);

	/*
	 * For consistency with the other functions we can't generate the
	 * true/false here.
	 */
	magic_res = *val != '\0' ? 2 : 1;
	free(val_freeIt);
	return magic_res;
}

static Boolean
FuncEmpty(size_t arglen, const char *arg MAKE_ATTR_UNUSED)
{
	/* Magic values ahead, see ParseEmptyArg. */
	return arglen == 1;
}

static Boolean
CondParser_Func(CondParser *par, Boolean doEval, Token *out_token)
{
	static const struct fn_def {
		const char *fn_name;
		size_t fn_name_len;
		size_t (*fn_parse)(const char **, Boolean, const char *,
				   char **);
		Boolean (*fn_eval)(size_t, const char *);
	} fns[] = {
		{ "defined",  7, ParseFuncArg,  FuncDefined },
		{ "make",     4, ParseFuncArg,  FuncMake },
		{ "exists",   6, ParseFuncArg,  FuncExists },
		{ "empty",    5, ParseEmptyArg, FuncEmpty },
		{ "target",   6, ParseFuncArg,  FuncTarget },
		{ "commands", 8, ParseFuncArg,  FuncCommands }
	};
	const struct fn_def *fn;
	char *arg = NULL;
	size_t arglen;
	const char *cp = par->p;
	const struct fn_def *fns_end = fns + sizeof fns / sizeof fns[0];

	for (fn = fns; fn != fns_end; fn++) {
		if (!is_token(cp, fn->fn_name, fn->fn_name_len))
			continue;

		cp += fn->fn_name_len;
		cpp_skip_whitespace(&cp);
		if (*cp != '(')
			break;

		arglen = fn->fn_parse(&cp, doEval, fn->fn_name, &arg);
		if (arglen == 0 || arglen == (size_t)-1) {
			par->p = cp;
			*out_token = arglen == 0 ? TOK_FALSE : TOK_ERROR;
			return TRUE;
		}

		/* Evaluate the argument using the required function. */
		*out_token = ToToken(!doEval || fn->fn_eval(arglen, arg));
		free(arg);
		par->p = cp;
		return TRUE;
	}

	return FALSE;
}

/* Parse a function call, a number, a variable expression or a string
 * literal. */
static Token
CondParser_LeafToken(CondParser *par, Boolean doEval)
{
	Token t;
	char *arg = NULL;
	size_t arglen;
	const char *cp;
	const char *cp1;

	if (CondParser_Func(par, doEval, &t))
		return t;

	/* Push anything numeric through the compare expression */
	cp = par->p;
	if (ch_isdigit(cp[0]) || cp[0] == '-' || cp[0] == '+')
		return CondParser_Comparison(par, doEval);

	/*
	 * Most likely we have a naked token to apply the default function to.
	 * However ".if a == b" gets here when the "a" is unquoted and doesn't
	 * start with a '$'. This surprises people.
	 * If what follows the function argument is a '=' or '!' then the
	 * syntax would be invalid if we did "defined(a)" - so instead treat
	 * as an expression.
	 */
	arglen = ParseFuncArg(&cp, doEval, NULL, &arg);
	cp1 = cp;
	cpp_skip_whitespace(&cp1);
	if (*cp1 == '=' || *cp1 == '!')
		return CondParser_Comparison(par, doEval);
	par->p = cp;

	/*
	 * Evaluate the argument using the default function.
	 * This path always treats .if as .ifdef. To get here, the character
	 * after .if must have been taken literally, so the argument cannot
	 * be empty - even if it contained a variable expansion.
	 */
	t = ToToken(!doEval || If_Eval(par->if_info, arg, arglen));
	free(arg);
	return t;
}

/* Return the next token or comparison result from the parser. */
static Token
CondParser_Token(CondParser *par, Boolean doEval)
{
	Token t;

	t = par->curr;
	if (t != TOK_NONE) {
		par->curr = TOK_NONE;
		return t;
	}

	cpp_skip_hspace(&par->p);

	switch (par->p[0]) {

	case '(':
		par->p++;
		return TOK_LPAREN;

	case ')':
		par->p++;
		return TOK_RPAREN;

	case '|':
		par->p++;
		if (par->p[0] == '|')
			par->p++;
		else if (opts.lint) {
			Parse_Error(PARSE_FATAL, "Unknown operator '|'");
			par->printedError = TRUE;
			return TOK_ERROR;
		}
		return TOK_OR;

	case '&':
		par->p++;
		if (par->p[0] == '&')
			par->p++;
		else if (opts.lint) {
			Parse_Error(PARSE_FATAL, "Unknown operator '&'");
			par->printedError = TRUE;
			return TOK_ERROR;
		}
		return TOK_AND;

	case '!':
		par->p++;
		return TOK_NOT;

	case '#':		/* XXX: see unit-tests/cond-token-plain.mk */
	case '\n':		/* XXX: why should this end the condition? */
		/* Probably obsolete now, from 1993-03-21. */
	case '\0':
		return TOK_EOF;

	case '"':
	case '$':
		return CondParser_Comparison(par, doEval);

	default:
		return CondParser_LeafToken(par, doEval);
	}
}

/* Parse a single term in the expression. This consists of a terminal symbol
 * or TOK_NOT and a term (not including the binary operators):
 *
 *	T -> defined(variable) | make(target) | exists(file) | symbol
 *	T -> ! T | ( E )
 *
 * Results:
 *	TOK_TRUE, TOK_FALSE or TOK_ERROR.
 */
static Token
CondParser_Term(CondParser *par, Boolean doEval)
{
	Token t;

	t = CondParser_Token(par, doEval);

	if (t == TOK_EOF) {
		/*
		 * If we reached the end of the expression, the expression
		 * is malformed...
		 */
		t = TOK_ERROR;
	} else if (t == TOK_LPAREN) {
		/*
		 * T -> ( E )
		 */
		t = CondParser_Expr(par, doEval);
		if (t != TOK_ERROR) {
			if (CondParser_Token(par, doEval) != TOK_RPAREN) {
				t = TOK_ERROR;
			}
		}
	} else if (t == TOK_NOT) {
		t = CondParser_Term(par, doEval);
		if (t == TOK_TRUE) {
			t = TOK_FALSE;
		} else if (t == TOK_FALSE) {
			t = TOK_TRUE;
		}
	}
	return t;
}

/* Parse a conjunctive factor (nice name, wot?)
 *
 *	F -> T && F | T
 *
 * Results:
 *	TOK_TRUE, TOK_FALSE or TOK_ERROR
 */
static Token
CondParser_Factor(CondParser *par, Boolean doEval)
{
	Token l, o;

	l = CondParser_Term(par, doEval);
	if (l != TOK_ERROR) {
		o = CondParser_Token(par, doEval);

		if (o == TOK_AND) {
			/*
			 * F -> T && F
			 *
			 * If T is TOK_FALSE, the whole thing will be
			 * TOK_FALSE, but we have to parse the r.h.s. anyway
			 * (to throw it away). If T is TOK_TRUE, the result
			 * is the r.h.s., be it a TOK_ERROR or not.
			 */
			if (l == TOK_TRUE) {
				l = CondParser_Factor(par, doEval);
			} else {
				(void)CondParser_Factor(par, FALSE);
			}
		} else {
			/*
			 * F -> T
			 */
			CondParser_PushBack(par, o);
		}
	}
	return l;
}

/* Main expression production.
 *
 *	E -> F || E | F
 *
 * Results:
 *	TOK_TRUE, TOK_FALSE or TOK_ERROR.
 */
static Token
CondParser_Expr(CondParser *par, Boolean doEval)
{
	Token l, o;

	l = CondParser_Factor(par, doEval);
	if (l != TOK_ERROR) {
		o = CondParser_Token(par, doEval);

		if (o == TOK_OR) {
			/*
			 * E -> F || E
			 *
			 * A similar thing occurs for ||, except that here
			 * we make sure the l.h.s. is TOK_FALSE before we
			 * bother to evaluate the r.h.s. Once again, if l
			 * is TOK_FALSE, the result is the r.h.s. and once
			 * again if l is TOK_TRUE, we parse the r.h.s. to
			 * throw it away.
			 */
			if (l == TOK_FALSE) {
				l = CondParser_Expr(par, doEval);
			} else {
				(void)CondParser_Expr(par, FALSE);
			}
		} else {
			/*
			 * E -> F
			 */
			CondParser_PushBack(par, o);
		}
	}
	return l;
}

static CondEvalResult
CondParser_Eval(CondParser *par, Boolean *value)
{
	Token res;

	DEBUG1(COND, "CondParser_Eval: %s\n", par->p);

	res = CondParser_Expr(par, TRUE);
	if (res != TOK_FALSE && res != TOK_TRUE)
		return COND_INVALID;

	if (CondParser_Token(par, FALSE) != TOK_EOF)
		return COND_INVALID;

	*value = res == TOK_TRUE;
	return COND_PARSE;
}

/* Evaluate the condition, including any side effects from the variable
 * expressions in the condition. The condition consists of &&, ||, !,
 * function(arg), comparisons and parenthetical groupings thereof.
 *
 * Results:
 *	COND_PARSE	if the condition was valid grammatically
 *	COND_INVALID	if not a valid conditional.
 *
 *	(*value) is set to the boolean value of the condition
 */
static CondEvalResult
CondEvalExpression(const struct If *info, const char *cond, Boolean *value,
		   Boolean eprint, Boolean strictLHS)
{
	CondParser par;
	CondEvalResult rval;

	lhsStrict = strictLHS;

	cpp_skip_hspace(&cond);

	par.if_info = info != NULL ? info : ifs + PLAIN_IF_INDEX;
	par.p = cond;
	par.curr = TOK_NONE;
	par.printedError = FALSE;

	rval = CondParser_Eval(&par, value);

	if (rval == COND_INVALID && eprint && !par.printedError)
		Parse_Error(PARSE_FATAL, "Malformed conditional (%s)", cond);

	return rval;
}

/* Evaluate a condition in a :? modifier, such as
 * ${"${VAR}" == value:?yes:no}. */
CondEvalResult
Cond_EvalCondition(const char *cond, Boolean *out_value)
{
	return CondEvalExpression(NULL, cond, out_value, FALSE, FALSE);
}

static Boolean
IsEndif(const char *p)
{
	return p[0] == 'e' && p[1] == 'n' && p[2] == 'd' &&
	       p[3] == 'i' && p[4] == 'f' && !ch_isalpha(p[5]);
}

/* Evaluate the conditional directive in the line, which is one of:
 *
 *	.if <cond>
 *	.ifmake <cond>
 *	.ifnmake <cond>
 *	.ifdef <cond>
 *	.ifndef <cond>
 *	.elif <cond>
 *	.elifmake <cond>
 *	.elifnmake <cond>
 *	.elifdef <cond>
 *	.elifndef <cond>
 *	.else
 *	.endif
 *
 * In these directives, <cond> consists of &&, ||, !, function(arg),
 * comparisons, expressions, bare words, numbers and strings, and
 * parenthetical groupings thereof.
 *
 * Results:
 *	COND_PARSE	to continue parsing the lines that follow the
 *			conditional (when <cond> evaluates to TRUE)
 *	COND_SKIP	to skip the lines after the conditional
 *			(when <cond> evaluates to FALSE, or when a previous
 *			branch has already been taken)
 *	COND_INVALID	if the conditional was not valid, either because of
 *			a syntax error or because some variable was undefined
 *			or because the condition could not be evaluated
 */
CondEvalResult
Cond_EvalLine(const char *line)
{
	typedef enum IfState {

		/* None of the previous <cond> evaluated to TRUE. */
		IFS_INITIAL	= 0,

		/* The previous <cond> evaluated to TRUE.
		 * The lines following this condition are interpreted. */
		IFS_ACTIVE	= 1 << 0,

		/* The previous directive was an '.else'. */
		IFS_SEEN_ELSE	= 1 << 1,

		/* One of the previous <cond> evaluated to TRUE. */
		IFS_WAS_ACTIVE	= 1 << 2

	} IfState;

	static enum IfState *cond_states = NULL;
	static unsigned int cond_states_cap = 128;

	const struct If *ifp;
	Boolean isElif;
	Boolean value;
	IfState state;
	const char *p = line;

	if (cond_states == NULL) {
		cond_states = bmake_malloc(
		    cond_states_cap * sizeof *cond_states);
		cond_states[0] = IFS_ACTIVE;
	}

	p++;			/* skip the leading '.' */
	cpp_skip_hspace(&p);

	if (IsEndif(p)) {	/* It is an '.endif'. */
		if (p[5] != '\0') {
			Parse_Error(PARSE_FATAL,
			    "The .endif directive does not take arguments.");
		}

		if (cond_depth == cond_min_depth) {
			Parse_Error(PARSE_FATAL, "if-less endif");
			return COND_PARSE;
		}

		/* Return state for previous conditional */
		cond_depth--;
		return cond_states[cond_depth] & IFS_ACTIVE
		    ? COND_PARSE : COND_SKIP;
	}

	/* Parse the name of the directive, such as 'if', 'elif', 'endif'. */
	if (p[0] == 'e') {
		if (p[1] != 'l') {
			/*
			 * Unknown directive.  It might still be a
			 * transformation rule like '.elisp.scm',
			 * therefore no error message here.
			 */
			return COND_INVALID;
		}

		/* Quite likely this is 'else' or 'elif' */
		p += 2;
		if (is_token(p, "se", 2)) {	/* It is an 'else'. */

			if (p[2] != '\0')
				Parse_Error(PARSE_FATAL,
					    "The .else directive "
					    "does not take arguments.");

			if (cond_depth == cond_min_depth) {
				Parse_Error(PARSE_FATAL, "if-less else");
				return COND_PARSE;
			}

			state = cond_states[cond_depth];
			if (state == IFS_INITIAL) {
				state = IFS_ACTIVE | IFS_SEEN_ELSE;
			} else {
				if (state & IFS_SEEN_ELSE)
					Parse_Error(PARSE_WARNING,
						    "extra else");
				state = IFS_WAS_ACTIVE | IFS_SEEN_ELSE;
			}
			cond_states[cond_depth] = state;

			return state & IFS_ACTIVE ? COND_PARSE : COND_SKIP;
		}
		/* Assume for now it is an elif */
		isElif = TRUE;
	} else
		isElif = FALSE;

	if (p[0] != 'i' || p[1] != 'f') {
		/*
		 * Unknown directive.  It might still be a transformation rule
		 * like '.elisp.scm', therefore no error message here.
		 */
		return COND_INVALID;	/* Not an ifxxx or elifxxx line */
	}

	/*
	 * Figure out what sort of conditional it is -- what its default
	 * function is, etc. -- by looking in the table of valid "ifs"
	 */
	p += 2;
	for (ifp = ifs;; ifp++) {
		if (ifp->form == NULL) {
			/*
			 * TODO: Add error message about unknown directive,
			 * since there is no other known directive that starts
			 * with 'el' or 'if'.
			 *
			 * Example: .elifx 123
			 */
			return COND_INVALID;
		}
		if (is_token(p, ifp->form, ifp->formlen)) {
			p += ifp->formlen;
			break;
		}
	}

	/* Now we know what sort of 'if' it is... */

	if (isElif) {
		if (cond_depth == cond_min_depth) {
			Parse_Error(PARSE_FATAL, "if-less elif");
			return COND_PARSE;
		}
		state = cond_states[cond_depth];
		if (state & IFS_SEEN_ELSE) {
			Parse_Error(PARSE_WARNING, "extra elif");
			cond_states[cond_depth] =
			    IFS_WAS_ACTIVE | IFS_SEEN_ELSE;
			return COND_SKIP;
		}
		if (state != IFS_INITIAL) {
			cond_states[cond_depth] = IFS_WAS_ACTIVE;
			return COND_SKIP;
		}
	} else {
		/* Normal .if */
		if (cond_depth + 1 >= cond_states_cap) {
			/*
			 * This is rare, but not impossible.
			 * In meta mode, dirdeps.mk (only runs at level 0)
			 * can need more than the default.
			 */
			cond_states_cap += 32;
			cond_states = bmake_realloc(cond_states,
						    cond_states_cap *
						    sizeof *cond_states);
		}
		state = cond_states[cond_depth];
		cond_depth++;
		if (!(state & IFS_ACTIVE)) {
			/*
			 * If we aren't parsing the data,
			 * treat as always false.
			 */
			cond_states[cond_depth] = IFS_WAS_ACTIVE;
			return COND_SKIP;
		}
	}

	/* And evaluate the conditional expression */
	if (CondEvalExpression(ifp, p, &value, TRUE, TRUE) == COND_INVALID) {
		/* Syntax error in conditional, error message already output. */
		/* Skip everything to matching .endif */
		/* XXX: An extra '.else' is not detected in this case. */
		cond_states[cond_depth] = IFS_WAS_ACTIVE;
		return COND_SKIP;
	}

	if (!value) {
		cond_states[cond_depth] = IFS_INITIAL;
		return COND_SKIP;
	}
	cond_states[cond_depth] = IFS_ACTIVE;
	return COND_PARSE;
}

void
Cond_restore_depth(unsigned int saved_depth)
{
	unsigned int open_conds = cond_depth - cond_min_depth;

	if (open_conds != 0 || saved_depth > cond_depth) {
		Parse_Error(PARSE_FATAL, "%u open conditional%s",
			    open_conds, open_conds == 1 ? "" : "s");
		cond_depth = cond_min_depth;
	}

	cond_min_depth = saved_depth;
}

unsigned int
Cond_save_depth(void)
{
	unsigned int depth = cond_min_depth;

	cond_min_depth = cond_depth;
	return depth;
}