value.cc - platform/build/kati - Gitiles

 // Copyright 2015 Google Inc. All rights reserved
 //
 // Licensed under the Apache License, Version 2.0 (the "License");
 // you may not use this file except in compliance with the License.
 // You may obtain a copy of the License at
 //
 //      http://www.apache.org/licenses/LICENSE-2.0
 //
 // Unless required by applicable law or agreed to in writing, software
 // distributed under the License is distributed on an "AS IS" BASIS,
 // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 // See the License for the specific language governing permissions and
 // limitations under the License.

 // +build ignore

 #include "value.h"

 #include <vector>

 #include "eval.h"
 #include "func.h"
 #include "log.h"
 #include "stringprintf.h"
 #include "strutil.h"
 #include "var.h"

 Evaluable::Evaluable() {
 }

 Evaluable::~Evaluable() {
 }

 shared_ptr<string> Evaluable::Eval(Evaluator* ev) const {
   shared_ptr<string> s = make_shared<string>();
   Eval(ev, s.get());
   return s;
 }

 Value::Value() {
 }

 Value::~Value() {
 }

 string Value::DebugString() const {
   if (static_cast<const Value*>(this)) {
     return NoLineBreak(DebugString_());
   }
   return "(null)";
 }

 class Literal : public Value {
  public:
   explicit Literal(StringPiece s)
       : s_(s) {
   }

   StringPiece val() const { return s_; }

   virtual void Eval(Evaluator*, string* s) const override {
     s->append(s_.begin(), s_.end());
   }

   virtual string DebugString_() const override {
     return s_.as_string();
   }

  private:
   StringPiece s_;
 };

 class Expr : public Value {
  public:
   Expr() {
   }

   virtual ~Expr() {
     for (Value* v : vals_) {
       delete v;
     }
   }

   // Takes the ownership of |v|.
   void AddValue(Value* v) {
     vals_.push_back(v);
   }

   virtual void Eval(Evaluator* ev, string* s) const override {
     for (Value* v : vals_) {
       v->Eval(ev, s);
     }
   }

   virtual string DebugString_() const override {
     string r;
     for (Value* v : vals_) {
       if (r.empty()) {
         r += "Expr(";
       } else {
         r += ", ";
       }
       r += v->DebugString();
     }
     if (!r.empty())
       r += ")";
     return r;
   }

   virtual Value* Compact() {
     if (vals_.size() != 1) {
       return this;
     }
     Value* r = vals_[0];
     vals_.clear();
     delete this;
     return r;
   }

  private:
   vector<Value*> vals_;
 };

 class SymRef : public Value {
  public:
   explicit SymRef(Symbol n)
       : name_(n) {
   }
   virtual ~SymRef() {
   }

   virtual shared_ptr<string> Eval(Evaluator* ev) const override {
     Var* v = ev->LookupVar(name_);
     return v->Eval(ev);
   }

   virtual void Eval(Evaluator* ev, string* s) const override {
     Var* v = ev->LookupVar(name_);
     v->Eval(ev, s);
   }

   virtual string DebugString_() const override {
     return StringPrintf("SymRef(%s)", name_.c_str());
   }

  private:
   Symbol name_;
 };

 class VarRef : public Value {
  public:
   explicit VarRef(Value* n)
       : name_(n) {
   }
   virtual ~VarRef() {
     delete name_;
   }

   virtual shared_ptr<string> Eval(Evaluator* ev) const override {
     shared_ptr<string> name = name_->Eval(ev);
     Var* v = ev->LookupVar(Intern(*name));
     return v->Eval(ev);
   }

   virtual void Eval(Evaluator* ev, string* s) const override {
     shared_ptr<string> name = name_->Eval(ev);
     Var* v = ev->LookupVar(Intern(*name));
     v->Eval(ev, s);
   }

   virtual string DebugString_() const override {
     return StringPrintf("VarRef(%s)", name_->DebugString().c_str());
   }

  private:
   Value* name_;
 };

 class VarSubst : public Value {
  public:
   explicit VarSubst(Value* n, Value* p, Value* s)
       : name_(n), pat_(p), subst_(s) {
   }
   virtual ~VarSubst() {
     delete name_;
     delete pat_;
     delete subst_;
   }

   virtual void Eval(Evaluator* ev, string* s) const override {
     shared_ptr<string> name = name_->Eval(ev);
     Var* v = ev->LookupVar(Intern(*name));
     shared_ptr<string> value = v->Eval(ev);
     shared_ptr<string> pat_str = pat_->Eval(ev);
     shared_ptr<string> subst = subst_->Eval(ev);
     WordWriter ww(s);
     Pattern pat(*pat_str);
     for (StringPiece tok : WordScanner(*value)) {
       ww.MaybeAddWhitespace();
       pat.AppendSubstRef(tok, *subst, s);
     }
   }

   virtual string DebugString_() const override {
     return StringPrintf("VarSubst(%s:%s=%s)",
                         name_->DebugString().c_str(),
                         pat_->DebugString().c_str(),
                         subst_->DebugString().c_str());
   }

  private:
   Value* name_;
   Value* pat_;
   Value* subst_;
 };

 class Func : public Value {
  public:
   explicit Func(FuncInfo* fi)
       : fi_(fi) {
   }

   ~Func() {
     for (Value* a : args_)
       delete a;
   }

   virtual void Eval(Evaluator* ev, string* s) const override {
     LOG("Invoke func %s(%s)", name(), JoinValues(args_, ",").c_str());
     fi_->func(args_, ev, s);
   }

   virtual string DebugString_() const override {
     return StringPrintf("Func(%s %s)",
                         fi_->name,
                         JoinValues(args_, ",").c_str());
   }

   void AddArg(Value* v) {
     args_.push_back(v);
   }

   const char* name() const { return fi_->name; }
   int arity() const { return fi_->arity; }
   int min_arity() const { return fi_->min_arity; }
   bool trim_space() const { return fi_->trim_space; }
   bool trim_right_space_1st() const { return fi_->trim_right_space_1st; }

  private:
   FuncInfo* fi_;
   vector<Value*> args_;
 };

 static char CloseParen(char c) {
   switch (c) {
     case '(':
       return ')';
     case '{':
       return '}';
   }
   return 0;
 }

 static size_t SkipSpaces(StringPiece s, const char* terms) {
   for (size_t i = 0; i < s.size(); i++) {
     char c = s[i];
     if (strchr(terms, c))
       return i;
     if (!isspace(c)) {
       if (c != '\\')
         return i;
       char n = s.get(i + 1);
       if (n != '\r' && n != '\n')
         return i;
     }
   }
   return s.size();
 }

 bool ShouldHandleComments(ParseExprOpt opt) {
   return opt != ParseExprOpt::DEFINE && opt != ParseExprOpt::COMMAND;
 }

 void ParseFunc(const Loc& loc,
                Func* f, StringPiece s, size_t i, char* terms,
                size_t* index_out) {
   terms[1] = ',';
   terms[2] = '\0';
   i += SkipSpaces(s.substr(i), terms);
   if (i == s.size()) {
     *index_out = i;
     return;
   }

   int nargs = 1;
   while (true) {
     if (f->arity() && nargs >= f->arity()) {
       terms[1] = '\0';  // Drop ','.
     }

     if (f->trim_space()) {
       for (; i < s.size(); i++) {
         if (isspace(s[i]))
           continue;
         if (s[i] == '\\') {
           char c = s.get(i+1);
           if (c == '\r' || c == '\n')
             continue;
         }
         break;
       }
     }
     const bool trim_right_space = (f->trim_space() ||
                                    (nargs == 1 && f->trim_right_space_1st()));
     size_t n;
     Value* v = ParseExprImpl(loc, s.substr(i), terms, ParseExprOpt::FUNC,
                              &n, trim_right_space);
     // TODO: concatLine???
     f->AddArg(v);
     i += n;
     if (i == s.size()) {
       ERROR("%s:%d: *** unterminated call to function '%s': "
             "missing '%c'.",
             LOCF(loc), f->name(), terms[0]);
     }
     nargs++;
     if (s[i] == terms[0]) {
       i++;
       break;
     }
     i++;  // Should be ','.
     if (i == s.size())
       break;
   }

   if (nargs <= f->min_arity()) {
     ERROR("%s:%d: *** insufficient number of arguments (%d) to function `%s'.",
           LOCF(loc), nargs - 1, f->name());
   }

   *index_out = i;
   return;
 }

 Value* ParseDollar(const Loc& loc, StringPiece s, size_t* index_out) {
   CHECK(s.size() >= 2);
   CHECK(s[0] == '$');
   CHECK(s[1] != '$');

   char cp = CloseParen(s[1]);
   if (cp == 0) {
     *index_out = 2;
     return new SymRef(Intern(s.substr(1, 1)));
   }

   char terms[] = {cp, ':', ' ', 0};
   for (size_t i = 2;;) {
     size_t n;
     Value* vname = ParseExprImpl(loc, s.substr(i), terms,
                                  ParseExprOpt::NORMAL, &n);
     i += n;
     if (s[i] == cp) {
       *index_out = i + 1;
       if (Literal* lit = dynamic_cast<Literal*>(vname)) {
         Value* r = new SymRef(Intern(lit->val()));
         delete lit;
         return r;
       }
       return new VarRef(vname);
     }

     if (s[i] == ' ' || s[i] == '\\') {
       // ${func ...}
       if (Literal* lit = dynamic_cast<Literal*>(vname)) {
         if (FuncInfo* fi = GetFuncInfo(lit->val())) {
           delete lit;
           Func* func = new Func(fi);
           ParseFunc(loc, func, s, i+1, terms, index_out);
           return func;
         }
       }

       // Not a function. Drop ' ' from |terms| and parse it
       // again. This is inefficient, but this code path should be
       // rarely used.
       delete vname;
       terms[2] = 0;
       i = 2;
       continue;
     }

     if (s[i] == ':') {
       terms[2] = '\0';
       terms[1] = '=';
       size_t n;
       Value* pat = ParseExprImpl(loc, s.substr(i+1), terms,
                                  ParseExprOpt::NORMAL, &n);
       i += 1 + n;
       if (s[i] == cp) {
         Expr* v = new Expr;
         v->AddValue(vname);
         v->AddValue(new Literal(":"));
         v->AddValue(pat);
         *index_out = i + 1;
         return new VarRef(v);
       }

       terms[1] = '\0';
       Value* subst = ParseExprImpl(loc, s.substr(i+1), terms,
                                    ParseExprOpt::NORMAL, &n);
       i += 1 + n;
       *index_out = i + 1;
       return new VarSubst(vname->Compact(), pat, subst);
     }

     // GNU make accepts expressions like $((). See unmatched_paren*.mk
     // for detail.
     size_t found = s.find(cp);
     if (found != string::npos) {
       *index_out = s.size();
       return new SymRef(Intern(s.substr(2, found-2)));
     }
     ERROR("%s:%d: *** unterminated variable reference.", LOCF(loc));
   }
 }

 Value* ParseExprImpl(const Loc& loc,
                      StringPiece s, const char* terms, ParseExprOpt opt,
                      size_t* index_out, bool trim_right_space) {
   if (s.get(s.size() - 1) == '\r')
     s.remove_suffix(1);

   Expr* r = new Expr;
   size_t b = 0;
   char save_paren = 0;
   int paren_depth = 0;
   size_t i;
   for (i = 0; i < s.size(); i++) {
     char c = s[i];
     if (terms && strchr(terms, c)) {
       break;
     }

     // Handle a comment.
     if (!terms && c == '#' && ShouldHandleComments(opt)) {
       if (i > b)
         r->AddValue(new Literal(s.substr(b, i-b)));
       bool was_backslash = false;
       for (; i < s.size() && !(s[i] == '\n' && !was_backslash); i++) {
         was_backslash = !was_backslash && s[i] == '\\';
       }
       *index_out = i;
       return r->Compact();
     }

     if (c == '$') {
       if (i + 1 >= s.size()) {
         break;
       }

       if (i > b)
         r->AddValue(new Literal(s.substr(b, i-b)));

       if (s[i+1] == '$') {
         r->AddValue(new Literal(StringPiece("$")));
         i += 1;
         b = i + 1;
         continue;
       }

       if (terms && strchr(terms, s[i+1])) {
         *index_out = i + 1;
         return r->Compact();
       }

       size_t n;
       Value* v = ParseDollar(loc, s.substr(i), &n);
       i += n;
       b = i;
       i--;
       r->AddValue(v);
       continue;
     }

     if ((c == '(' || c == '{') && opt == ParseExprOpt::FUNC) {
       char cp = CloseParen(c);
       if (terms && terms[0] == cp) {
         paren_depth++;
         save_paren = cp;
         terms++;
       } else if (cp == save_paren) {
         paren_depth++;
       }
       continue;
     }

     if (c == save_paren) {
       paren_depth--;
       if (paren_depth == 0) {
         terms--;
         save_paren = 0;
       }
     }

     if (c == '\\' && i + 1 < s.size() && opt != ParseExprOpt::COMMAND) {
       char n = s[i+1];
       if (n == '\\') {
         i++;
         continue;
       }
       if (n == '#' && ShouldHandleComments(opt)) {
         r->AddValue(new Literal(s.substr(b, i-b)));
         i++;
         b = i;
         continue;
       }
       if (n == '\r' || n == '\n') {
         if (terms && strchr(terms, ' ')) {
           break;
         }
         if (i > b) {
           r->AddValue(new Literal(TrimRightSpace(s.substr(b, i-b))));
         }
         r->AddValue(new Literal(StringPiece(" ")));
         for (i++; i < s.size(); i++) {
           if (!isspace(s[i]) &&
               (s[i] != '\\' || (s.get(i+1) != '\r' && s.get(i+1) != '\n'))) {
             break;
           }
         }
         b = i;
         i--;
       }
     }
   }

   if (i > b) {
     StringPiece rest = s.substr(b, i-b);
     if (trim_right_space)
       rest = TrimRightSpace(rest);
     if (!rest.empty())
       r->AddValue(new Literal(rest));
   }
   *index_out = i;
   return r->Compact();
 }

 Value* ParseExpr(const Loc& loc, StringPiece s, ParseExprOpt opt) {
   size_t n;
   return ParseExprImpl(loc, s, NULL, opt, &n);
 }

 string JoinValues(const vector<Value*>& vals, const char* sep) {
   vector<string> val_strs;
   for (Value* v : vals) {
     val_strs.push_back(v->DebugString());
   }
   return JoinStrings(val_strs, sep);
 }

 Value* NewExpr2(Value* v1, Value* v2) {
   Expr* e = new Expr();
   e->AddValue(v1);
   e->AddValue(v2);
   return e;
 }

 Value* NewExpr3(Value* v1, Value* v2, Value* v3) {
   Expr* e = new Expr();
   e->AddValue(v1);
   e->AddValue(v2);
   e->AddValue(v3);
   return e;
 }

 Value* NewLiteral(StringPiece s) {
   return new Literal(s);
 }
	// Copyright 2015 Google Inc. All rights reserved
	//
	// Licensed under the Apache License, Version 2.0 (the "License");
	// you may not use this file except in compliance with the License.
	// You may obtain a copy of the License at
	//
	// http://www.apache.org/licenses/LICENSE-2.0
	//
	// Unless required by applicable law or agreed to in writing, software
	// distributed under the License is distributed on an "AS IS" BASIS,
	// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
	// See the License for the specific language governing permissions and
	// limitations under the License.

	// +build ignore

	#include "value.h"

	#include <vector>

	#include "eval.h"
	#include "func.h"
	#include "log.h"
	#include "stringprintf.h"
	#include "strutil.h"
	#include "var.h"

	Evaluable::Evaluable() {
	}

	Evaluable::~Evaluable() {
	}

	shared_ptr<string> Evaluable::Eval(Evaluator* ev) const {
	shared_ptr<string> s = make_shared<string>();
	Eval(ev, s.get());
	return s;
	}

	Value::Value() {
	}

	Value::~Value() {
	}

	string Value::DebugString() const {
	if (static_cast<const Value*>(this)) {
	return NoLineBreak(DebugString_());
	}
	return "(null)";
	}

	class Literal : public Value {
	public:
	explicit Literal(StringPiece s)
	: s_(s) {
	}

	StringPiece val() const { return s_; }

	virtual void Eval(Evaluator, string s) const override {
	s->append(s_.begin(), s_.end());
	}

	virtual string DebugString_() const override {
	return s_.as_string();
	}

	private:
	StringPiece s_;
	};

	class Expr : public Value {
	public:
	Expr() {
	}

	virtual ~Expr() {
	for (Value* v : vals_) {
	delete v;
	}
	}

	// Takes the ownership of \|v\|.
	void AddValue(Value* v) {
	vals_.push_back(v);
	}

	virtual void Eval(Evaluator* ev, string* s) const override {
	for (Value* v : vals_) {
	v->Eval(ev, s);
	}
	}

	virtual string DebugString_() const override {
	string r;
	for (Value* v : vals_) {
	if (r.empty()) {
	r += "Expr(";
	} else {
	r += ", ";
	}
	r += v->DebugString();
	}
	if (!r.empty())
	r += ")";
	return r;
	}

	virtual Value* Compact() {
	if (vals_.size() != 1) {
	return this;
	}
	Value* r = vals_[0];
	vals_.clear();
	delete this;
	return r;
	}

	private:
	vector<Value*> vals_;
	};

	class SymRef : public Value {
	public:
	explicit SymRef(Symbol n)
	: name_(n) {
	}
	virtual ~SymRef() {
	}

	virtual shared_ptr<string> Eval(Evaluator* ev) const override {
	Var* v = ev->LookupVar(name_);
	return v->Eval(ev);
	}

	virtual void Eval(Evaluator* ev, string* s) const override {
	Var* v = ev->LookupVar(name_);
	v->Eval(ev, s);
	}

	virtual string DebugString_() const override {
	return StringPrintf("SymRef(%s)", name_.c_str());
	}

	private:
	Symbol name_;
	};

	class VarRef : public Value {
	public:
	explicit VarRef(Value* n)
	: name_(n) {
	}
	virtual ~VarRef() {
	delete name_;
	}

	virtual shared_ptr<string> Eval(Evaluator* ev) const override {
	shared_ptr<string> name = name_->Eval(ev);
	Var* v = ev->LookupVar(Intern(*name));
	return v->Eval(ev);
	}

	virtual void Eval(Evaluator* ev, string* s) const override {
	shared_ptr<string> name = name_->Eval(ev);
	Var* v = ev->LookupVar(Intern(*name));
	v->Eval(ev, s);
	}

	virtual string DebugString_() const override {
	return StringPrintf("VarRef(%s)", name_->DebugString().c_str());
	}

	private:
	Value* name_;
	};

	class VarSubst : public Value {
	public:
	explicit VarSubst(Value* n, Value* p, Value* s)
	: name_(n), pat_(p), subst_(s) {
	}
	virtual ~VarSubst() {
	delete name_;
	delete pat_;
	delete subst_;
	}

	virtual void Eval(Evaluator* ev, string* s) const override {
	shared_ptr<string> name = name_->Eval(ev);
	Var* v = ev->LookupVar(Intern(*name));
	shared_ptr<string> value = v->Eval(ev);
	shared_ptr<string> pat_str = pat_->Eval(ev);
	shared_ptr<string> subst = subst_->Eval(ev);
	WordWriter ww(s);
	Pattern pat(*pat_str);
	for (StringPiece tok : WordScanner(*value)) {
	ww.MaybeAddWhitespace();
	pat.AppendSubstRef(tok, *subst, s);
	}
	}

	virtual string DebugString_() const override {
	return StringPrintf("VarSubst(%s:%s=%s)",
	name_->DebugString().c_str(),
	pat_->DebugString().c_str(),
	subst_->DebugString().c_str());
	}

	private:
	Value* name_;
	Value* pat_;
	Value* subst_;
	};

	class Func : public Value {
	public:
	explicit Func(FuncInfo* fi)
	: fi_(fi) {
	}

	~Func() {
	for (Value* a : args_)
	delete a;
	}

	virtual void Eval(Evaluator* ev, string* s) const override {
	LOG("Invoke func %s(%s)", name(), JoinValues(args_, ",").c_str());
	fi_->func(args_, ev, s);
	}

	virtual string DebugString_() const override {
	return StringPrintf("Func(%s %s)",
	fi_->name,
	JoinValues(args_, ",").c_str());
	}

	void AddArg(Value* v) {
	args_.push_back(v);
	}

	const char* name() const { return fi_->name; }
	int arity() const { return fi_->arity; }
	int min_arity() const { return fi_->min_arity; }
	bool trim_space() const { return fi_->trim_space; }
	bool trim_right_space_1st() const { return fi_->trim_right_space_1st; }

	private:
	FuncInfo* fi_;
	vector<Value*> args_;
	};

	static char CloseParen(char c) {
	switch (c) {
	case '(':
	return ')';
	case '{':
	return '}';
	}
	return 0;
	}

	static size_t SkipSpaces(StringPiece s, const char* terms) {
	for (size_t i = 0; i < s.size(); i++) {
	char c = s[i];
	if (strchr(terms, c))
	return i;
	if (!isspace(c)) {
	if (c != '\\')
	return i;
	char n = s.get(i + 1);
	if (n != '\r' && n != '\n')
	return i;
	}
	}
	return s.size();
	}

	bool ShouldHandleComments(ParseExprOpt opt) {
	return opt != ParseExprOpt::DEFINE && opt != ParseExprOpt::COMMAND;
	}

	void ParseFunc(const Loc& loc,
	Func* f, StringPiece s, size_t i, char* terms,
	size_t* index_out) {
	terms[1] = ',';
	terms[2] = '\0';
	i += SkipSpaces(s.substr(i), terms);
	if (i == s.size()) {
	*index_out = i;
	return;
	}

	int nargs = 1;
	while (true) {
	if (f->arity() && nargs >= f->arity()) {
	terms[1] = '\0'; // Drop ','.
	}

	if (f->trim_space()) {
	for (; i < s.size(); i++) {
	if (isspace(s[i]))
	continue;
	if (s[i] == '\\') {
	char c = s.get(i+1);
	if (c == '\r' \|\| c == '\n')
	continue;
	}
	break;
	}
	}
	const bool trim_right_space = (f->trim_space() \|\|
	(nargs == 1 && f->trim_right_space_1st()));
	size_t n;
	Value* v = ParseExprImpl(loc, s.substr(i), terms, ParseExprOpt::FUNC,
	&n, trim_right_space);
	// TODO: concatLine???
	f->AddArg(v);
	i += n;
	if (i == s.size()) {
	ERROR("%s:%d: *** unterminated call to function '%s': "
	"missing '%c'.",
	LOCF(loc), f->name(), terms[0]);
	}
	nargs++;
	if (s[i] == terms[0]) {
	i++;
	break;
	}
	i++; // Should be ','.
	if (i == s.size())
	break;
	}

	if (nargs <= f->min_arity()) {
	ERROR("%s:%d: *** insufficient number of arguments (%d) to function `%s'.",
	LOCF(loc), nargs - 1, f->name());
	}

	*index_out = i;
	return;
	}

	Value* ParseDollar(const Loc& loc, StringPiece s, size_t* index_out) {
	CHECK(s.size() >= 2);
	CHECK(s[0] == '$');
	CHECK(s[1] != '$');

	char cp = CloseParen(s[1]);
	if (cp == 0) {
	*index_out = 2;
	return new SymRef(Intern(s.substr(1, 1)));
	}

	char terms[] = {cp, ':', ' ', 0};
	for (size_t i = 2;;) {
	size_t n;
	Value* vname = ParseExprImpl(loc, s.substr(i), terms,
	ParseExprOpt::NORMAL, &n);
	i += n;
	if (s[i] == cp) {
	*index_out = i + 1;
	if (Literal* lit = dynamic_cast<Literal*>(vname)) {
	Value* r = new SymRef(Intern(lit->val()));
	delete lit;
	return r;
	}
	return new VarRef(vname);
	}

	if (s[i] == ' ' \|\| s[i] == '\\') {
	// ${func ...}
	if (Literal* lit = dynamic_cast<Literal*>(vname)) {
	if (FuncInfo* fi = GetFuncInfo(lit->val())) {
	delete lit;
	Func* func = new Func(fi);
	ParseFunc(loc, func, s, i+1, terms, index_out);
	return func;
	}
	}

	// Not a function. Drop ' ' from \|terms\| and parse it
	// again. This is inefficient, but this code path should be
	// rarely used.
	delete vname;
	terms[2] = 0;
	i = 2;
	continue;
	}

	if (s[i] == ':') {
	terms[2] = '\0';
	terms[1] = '=';
	size_t n;
	Value* pat = ParseExprImpl(loc, s.substr(i+1), terms,
	ParseExprOpt::NORMAL, &n);
	i += 1 + n;
	if (s[i] == cp) {
	Expr* v = new Expr;
	v->AddValue(vname);
	v->AddValue(new Literal(":"));
	v->AddValue(pat);
	*index_out = i + 1;
	return new VarRef(v);
	}

	terms[1] = '\0';
	Value* subst = ParseExprImpl(loc, s.substr(i+1), terms,
	ParseExprOpt::NORMAL, &n);
	i += 1 + n;
	*index_out = i + 1;
	return new VarSubst(vname->Compact(), pat, subst);
	}

	// GNU make accepts expressions like $((). See unmatched_paren*.mk
	// for detail.
	size_t found = s.find(cp);
	if (found != string::npos) {
	*index_out = s.size();
	return new SymRef(Intern(s.substr(2, found-2)));
	}
	ERROR("%s:%d: *** unterminated variable reference.", LOCF(loc));
	}
	}

	Value* ParseExprImpl(const Loc& loc,
	StringPiece s, const char* terms, ParseExprOpt opt,
	size_t* index_out, bool trim_right_space) {
	if (s.get(s.size() - 1) == '\r')
	s.remove_suffix(1);

	Expr* r = new Expr;
	size_t b = 0;
	char save_paren = 0;
	int paren_depth = 0;
	size_t i;
	for (i = 0; i < s.size(); i++) {
	char c = s[i];
	if (terms && strchr(terms, c)) {
	break;
	}

	// Handle a comment.
	if (!terms && c == '#' && ShouldHandleComments(opt)) {
	if (i > b)
	r->AddValue(new Literal(s.substr(b, i-b)));
	bool was_backslash = false;
	for (; i < s.size() && !(s[i] == '\n' && !was_backslash); i++) {
	was_backslash = !was_backslash && s[i] == '\\';
	}
	*index_out = i;
	return r->Compact();
	}

	if (c == '$') {
	if (i + 1 >= s.size()) {
	break;
	}

	if (i > b)
	r->AddValue(new Literal(s.substr(b, i-b)));

	if (s[i+1] == '$') {
	r->AddValue(new Literal(StringPiece("$")));
	i += 1;
	b = i + 1;
	continue;
	}

	if (terms && strchr(terms, s[i+1])) {
	*index_out = i + 1;
	return r->Compact();
	}

	size_t n;
	Value* v = ParseDollar(loc, s.substr(i), &n);
	i += n;
	b = i;
	i--;
	r->AddValue(v);
	continue;
	}

	if ((c == '(' \|\| c == '{') && opt == ParseExprOpt::FUNC) {
	char cp = CloseParen(c);
	if (terms && terms[0] == cp) {
	paren_depth++;
	save_paren = cp;
	terms++;
	} else if (cp == save_paren) {
	paren_depth++;
	}
	continue;
	}

	if (c == save_paren) {
	paren_depth--;
	if (paren_depth == 0) {
	terms--;
	save_paren = 0;
	}
	}

	if (c == '\\' && i + 1 < s.size() && opt != ParseExprOpt::COMMAND) {
	char n = s[i+1];
	if (n == '\\') {
	i++;
	continue;
	}
	if (n == '#' && ShouldHandleComments(opt)) {
	r->AddValue(new Literal(s.substr(b, i-b)));
	i++;
	b = i;
	continue;
	}
	if (n == '\r' \|\| n == '\n') {
	if (terms && strchr(terms, ' ')) {
	break;
	}
	if (i > b) {
	r->AddValue(new Literal(TrimRightSpace(s.substr(b, i-b))));
	}
	r->AddValue(new Literal(StringPiece(" ")));
	for (i++; i < s.size(); i++) {
	if (!isspace(s[i]) &&
	(s[i] != '\\' \|\| (s.get(i+1) != '\r' && s.get(i+1) != '\n'))) {
	break;
	}
	}
	b = i;
	i--;
	}
	}
	}

	if (i > b) {
	StringPiece rest = s.substr(b, i-b);
	if (trim_right_space)
	rest = TrimRightSpace(rest);
	if (!rest.empty())
	r->AddValue(new Literal(rest));
	}
	*index_out = i;
	return r->Compact();
	}

	Value* ParseExpr(const Loc& loc, StringPiece s, ParseExprOpt opt) {
	size_t n;
	return ParseExprImpl(loc, s, NULL, opt, &n);
	}

	string JoinValues(const vector<Value>& vals, const char sep) {
	vector<string> val_strs;
	for (Value* v : vals) {
	val_strs.push_back(v->DebugString());
	}
	return JoinStrings(val_strs, sep);
	}

	Value* NewExpr2(Value* v1, Value* v2) {
	Expr* e = new Expr();
	e->AddValue(v1);
	e->AddValue(v2);
	return e;
	}

	Value* NewExpr3(Value* v1, Value* v2, Value* v3) {
	Expr* e = new Expr();
	e->AddValue(v1);
	e->AddValue(v2);
	e->AddValue(v3);
	return e;
	}

	Value* NewLiteral(StringPiece s) {
	return new Literal(s);
	}