src/OpenGL/compiler/preprocessor/DirectiveParser.cpp

// Copyright 2016 The SwiftShader Authors. 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.

#include "DirectiveParser.h"

#include <algorithm>
#include <cassert>
#include <cstdlib>
#include <sstream>

#include "DiagnosticsBase.h"
#include "DirectiveHandlerBase.h"
#include "ExpressionParser.h"
#include "MacroExpander.h"
#include "Token.h"
#include "Tokenizer.h"

namespace {
enum DirectiveType
{
	DIRECTIVE_NONE,
	DIRECTIVE_DEFINE,
	DIRECTIVE_UNDEF,
	DIRECTIVE_IF,
	DIRECTIVE_IFDEF,
	DIRECTIVE_IFNDEF,
	DIRECTIVE_ELSE,
	DIRECTIVE_ELIF,
	DIRECTIVE_ENDIF,
	DIRECTIVE_ERROR,
	DIRECTIVE_PRAGMA,
	DIRECTIVE_EXTENSION,
	DIRECTIVE_VERSION,
	DIRECTIVE_LINE
};
}  // namespace

static DirectiveType getDirective(const pp::Token *token)
{
	static const char kDirectiveDefine[] = "define";
	static const char kDirectiveUndef[] = "undef";
	static const char kDirectiveIf[] = "if";
	static const char kDirectiveIfdef[] = "ifdef";
	static const char kDirectiveIfndef[] = "ifndef";
	static const char kDirectiveElse[] = "else";
	static const char kDirectiveElif[] = "elif";
	static const char kDirectiveEndif[] = "endif";
	static const char kDirectiveError[] = "error";
	static const char kDirectivePragma[] = "pragma";
	static const char kDirectiveExtension[] = "extension";
	static const char kDirectiveVersion[] = "version";
	static const char kDirectiveLine[] = "line";

	if (token->type != pp::Token::IDENTIFIER)
		return DIRECTIVE_NONE;

	if (token->text == kDirectiveDefine)
		return DIRECTIVE_DEFINE;
	else if (token->text == kDirectiveUndef)
		return DIRECTIVE_UNDEF;
	else if (token->text == kDirectiveIf)
		return DIRECTIVE_IF;
	else if (token->text == kDirectiveIfdef)
		return DIRECTIVE_IFDEF;
	else if (token->text == kDirectiveIfndef)
		return DIRECTIVE_IFNDEF;
	else if (token->text == kDirectiveElse)
		return DIRECTIVE_ELSE;
	else if (token->text == kDirectiveElif)
		return DIRECTIVE_ELIF;
	else if (token->text == kDirectiveEndif)
		return DIRECTIVE_ENDIF;
	else if (token->text == kDirectiveError)
		return DIRECTIVE_ERROR;
	else if (token->text == kDirectivePragma)
		return DIRECTIVE_PRAGMA;
	else if (token->text == kDirectiveExtension)
		return DIRECTIVE_EXTENSION;
	else if (token->text == kDirectiveVersion)
		return DIRECTIVE_VERSION;
	else if (token->text == kDirectiveLine)
		return DIRECTIVE_LINE;

	return DIRECTIVE_NONE;
}

static bool isConditionalDirective(DirectiveType directive)
{
	switch (directive)
	{
	case DIRECTIVE_IF:
	case DIRECTIVE_IFDEF:
	case DIRECTIVE_IFNDEF:
	case DIRECTIVE_ELSE:
	case DIRECTIVE_ELIF:
	case DIRECTIVE_ENDIF:
		return true;
	default:
		return false;
	}
}

// Returns true if the token represents End Of Directive.
static bool isEOD(const pp::Token *token)
{
	return (token->type == '\n') || (token->type == pp::Token::LAST);
}

static void skipUntilEOD(pp::Lexer *lexer, pp::Token *token)
{
	while(!isEOD(token))
	{
		lexer->lex(token);
	}
}

static bool isMacroNameReserved(const std::string& name)
{
	// Names prefixed with "GL_" are reserved.
	return (name.substr(0, 3) == "GL_");
}

bool hasDoubleUnderscores(const std::string &name)
{
	return (name.find("__") != std::string::npos);
}

static bool isMacroPredefined(const std::string& name,
                              const pp::MacroSet& macroSet)
{
	pp::MacroSet::const_iterator iter = macroSet.find(name);
	return iter != macroSet.end() ? iter->second->predefined : false;
}

namespace pp
{

class DefinedParser : public Lexer
{
public:
	DefinedParser(Lexer *lexer, const MacroSet *macroSet, Diagnostics *diagnostics)
		: mLexer(lexer), mMacroSet(macroSet), mDiagnostics(diagnostics)
	{
	}

protected:
	void lex(Token *token) override
	{
		const char kDefined[] = "defined";

		mLexer->lex(token);
		if (token->type != Token::IDENTIFIER)
			return;
		if (token->text != kDefined)
			return;

		bool paren = false;
		mLexer->lex(token);
		if (token->type == '(')
		{
			paren = true;
			mLexer->lex(token);
		}

		if (token->type != Token::IDENTIFIER)
		{
			mDiagnostics->report(Diagnostics::PP_UNEXPECTED_TOKEN, token->location, token->text);
			skipUntilEOD(mLexer, token);
			return;
		}
		MacroSet::const_iterator iter = mMacroSet->find(token->text);
		std::string expression = iter != mMacroSet->end() ? "1" : "0";

		if (paren)
		{
			mLexer->lex(token);
			if (token->type != ')')
			{
				mDiagnostics->report(Diagnostics::PP_UNEXPECTED_TOKEN,
				                     token->location, token->text);
				skipUntilEOD(mLexer, token);
				return;
			}
		}

		// We have a valid defined operator.
		// Convert the current token into a CONST_INT token.
		token->type = Token::CONST_INT;
		token->text = expression;
	}

private:
	Lexer *mLexer;
	const MacroSet *mMacroSet;
	Diagnostics *mDiagnostics;
};

DirectiveParser::DirectiveParser(Tokenizer *tokenizer,
                                 MacroSet *macroSet,
                                 Diagnostics *diagnostics,
                                 DirectiveHandler *directiveHandler,
                                 int maxMacroExpansionDepth)
    : mPastFirstStatement(false),
      mSeenNonPreprocessorToken(false),
      mTokenizer(tokenizer),
      mMacroSet(macroSet),
      mDiagnostics(diagnostics),
      mDirectiveHandler(directiveHandler),
      mShaderVersion(100),
      mMaxMacroExpansionDepth(maxMacroExpansionDepth)
{
}

DirectiveParser::~DirectiveParser()
{
}

void DirectiveParser::lex(Token *token)
{
	do
	{
		mTokenizer->lex(token);

		if (token->type == Token::PP_HASH)
		{
			parseDirective(token);
			mPastFirstStatement = true;
		}
		else if (!isEOD(token))
		{
			mSeenNonPreprocessorToken = true;
		}

		if (token->type == Token::LAST)
		{
			if (!mConditionalStack.empty())
			{
				const ConditionalBlock &block = mConditionalStack.back();
				mDiagnostics->report(Diagnostics::PP_CONDITIONAL_UNTERMINATED,
				                     block.location, block.type);
			}
			break;
		}

	} while (skipping() || (token->type == '\n'));

	mPastFirstStatement = true;
}

void DirectiveParser::parseDirective(Token *token)
{
	assert(token->type == Token::PP_HASH);

	mTokenizer->lex(token);
	if (isEOD(token))
	{
		// Empty Directive.
		return;
	}

	DirectiveType directive = getDirective(token);

	// While in an excluded conditional block/group,
	// we only parse conditional directives.
	if (skipping() && !isConditionalDirective(directive))
	{
		skipUntilEOD(mTokenizer, token);
		return;
	}

	switch(directive)
	{
	case DIRECTIVE_NONE:
		mDiagnostics->report(Diagnostics::PP_DIRECTIVE_INVALID_NAME,
		                     token->location, token->text);
		skipUntilEOD(mTokenizer, token);
		break;
	case DIRECTIVE_DEFINE:
		parseDefine(token);
		break;
	case DIRECTIVE_UNDEF:
		parseUndef(token);
		break;
	case DIRECTIVE_IF:
		parseIf(token);
		break;
	case DIRECTIVE_IFDEF:
		parseIfdef(token);
		break;
	case DIRECTIVE_IFNDEF:
		parseIfndef(token);
		break;
	case DIRECTIVE_ELSE:
		parseElse(token);
		break;
	case DIRECTIVE_ELIF:
		parseElif(token);
		break;
	case DIRECTIVE_ENDIF:
		parseEndif(token);
		break;
	case DIRECTIVE_ERROR:
		parseError(token);
		break;
	case DIRECTIVE_PRAGMA:
		parsePragma(token);
		break;
	case DIRECTIVE_EXTENSION:
		parseExtension(token);
		break;
	case DIRECTIVE_VERSION:
		parseVersion(token);
		break;
	case DIRECTIVE_LINE:
		parseLine(token);
		break;
	default:
		assert(false);
		break;
	}

	skipUntilEOD(mTokenizer, token);
	if (token->type == Token::LAST)
	{
		mDiagnostics->report(Diagnostics::PP_EOF_IN_DIRECTIVE,
		                     token->location, token->text);
	}
}

void DirectiveParser::parseDefine(Token *token)
{
	assert(getDirective(token) == DIRECTIVE_DEFINE);

	mTokenizer->lex(token);
	if (token->type != Token::IDENTIFIER)
	{
		mDiagnostics->report(Diagnostics::PP_UNEXPECTED_TOKEN,
		                     token->location, token->text);
		return;
	}
	if (isMacroPredefined(token->text, *mMacroSet))
	{
		mDiagnostics->report(Diagnostics::PP_MACRO_PREDEFINED_REDEFINED,
		                     token->location, token->text);
		return;
	}
	if (isMacroNameReserved(token->text))
	{
		mDiagnostics->report(Diagnostics::PP_MACRO_NAME_RESERVED,
		                     token->location, token->text);
		return;
	}
	// Using double underscores is allowed, but may result in unintended
	// behavior, so a warning is issued. At the time of writing this was
	// specified in ESSL 3.10, but the intent judging from Khronos
	// discussions and dEQP tests was that double underscores should be
	// allowed in earlier ESSL versions too.
	if (hasDoubleUnderscores(token->text))
	{
		mDiagnostics->report(Diagnostics::PP_WARNING_MACRO_NAME_RESERVED, token->location,
		                     token->text);
	}

	std::shared_ptr<Macro> macro = std::make_shared<Macro>();
	macro->type = Macro::kTypeObj;
	macro->name = token->text;

	mTokenizer->lex(token);
	if (token->type == '(' && !token->hasLeadingSpace())
	{
		// Function-like macro. Collect arguments.
		macro->type = Macro::kTypeFunc;
		do {
			mTokenizer->lex(token);
			if (token->type != Token::IDENTIFIER)
				break;

			if (std::find(macro->parameters.begin(), macro->parameters.end(), token->text) != macro->parameters.end())
			{
				mDiagnostics->report(Diagnostics::PP_MACRO_DUPLICATE_PARAMETER_NAMES,
				                     token->location, token->text);
				return;
			}

			macro->parameters.push_back(token->text);

			mTokenizer->lex(token);  // Get ','.
		} while (token->type == ',');

		if (token->type != ')')
		{
			mDiagnostics->report(Diagnostics::PP_UNEXPECTED_TOKEN,
			                     token->location,
			                     token->text);
			return;
		}
		mTokenizer->lex(token);  // Get ')'.
	}

	while ((token->type != '\n') && (token->type != Token::LAST))
	{
		// Reset the token location because it is unnecessary in replacement
		// list. Resetting it also allows us to reuse Token::equals() to
		// compare macros.
		token->location = SourceLocation();
		macro->replacements.push_back(*token);
		mTokenizer->lex(token);
	}
	if (!macro->replacements.empty())
	{
		// Whitespace preceding the replacement list is not considered part of
		// the replacement list for either form of macro.
		macro->replacements.front().setHasLeadingSpace(false);
	}

	// Check for macro redefinition.
	MacroSet::const_iterator iter = mMacroSet->find(macro->name);
	if (iter != mMacroSet->end() && !macro->equals(*iter->second))
	{
		mDiagnostics->report(Diagnostics::PP_MACRO_REDEFINED, token->location, macro->name);
		return;
	}
	mMacroSet->insert(std::make_pair(macro->name, macro));
}

void DirectiveParser::parseUndef(Token *token)
{
	assert(getDirective(token) == DIRECTIVE_UNDEF);

	mTokenizer->lex(token);
	if (token->type != Token::IDENTIFIER)
	{
		mDiagnostics->report(Diagnostics::PP_UNEXPECTED_TOKEN,
		                     token->location, token->text);
		return;
	}

	MacroSet::iterator iter = mMacroSet->find(token->text);
	if (iter != mMacroSet->end())
	{
		if (iter->second->predefined)
		{
			mDiagnostics->report(Diagnostics::PP_MACRO_PREDEFINED_UNDEFINED,
			                     token->location, token->text);
			return;
		}
		else if (iter->second->expansionCount > 0)
		{
			mDiagnostics->report(Diagnostics::PP_MACRO_UNDEFINED_WHILE_INVOKED,
			                     token->location, token->text);
			return;
		}
		else
		{
			mMacroSet->erase(iter);
		}
	}

	mTokenizer->lex(token);
	if (!isEOD(token))
	{
		mDiagnostics->report(Diagnostics::PP_UNEXPECTED_TOKEN, token->location, token->text);
		skipUntilEOD(mTokenizer, token);
	}
}

void DirectiveParser::parseIf(Token *token)
{
	assert(getDirective(token) == DIRECTIVE_IF);
	parseConditionalIf(token);
}

void DirectiveParser::parseIfdef(Token *token)
{
	assert(getDirective(token) == DIRECTIVE_IFDEF);
	parseConditionalIf(token);
}

void DirectiveParser::parseIfndef(Token *token)
{
	assert(getDirective(token) == DIRECTIVE_IFNDEF);
	parseConditionalIf(token);
}

void DirectiveParser::parseElse(Token *token)
{
	assert(getDirective(token) == DIRECTIVE_ELSE);

	if (mConditionalStack.empty())
	{
		mDiagnostics->report(Diagnostics::PP_CONDITIONAL_ELSE_WITHOUT_IF,
		                     token->location, token->text);
		skipUntilEOD(mTokenizer, token);
		return;
	}

	ConditionalBlock &block = mConditionalStack.back();
	if (block.skipBlock)
	{
		// No diagnostics. Just skip the whole line.
		skipUntilEOD(mTokenizer, token);
		return;
	}
	if (block.foundElseGroup)
	{
		mDiagnostics->report(Diagnostics::PP_CONDITIONAL_ELSE_AFTER_ELSE,
		                     token->location, token->text);
		skipUntilEOD(mTokenizer, token);
		return;
	}

	block.foundElseGroup = true;
	block.skipGroup = block.foundValidGroup;
	block.foundValidGroup = true;

	// Check if there are extra tokens after #else.
	mTokenizer->lex(token);
	if (!isEOD(token))
	{
		mDiagnostics->report(Diagnostics::PP_CONDITIONAL_UNEXPECTED_TOKEN,
		                     token->location, token->text);
		skipUntilEOD(mTokenizer, token);
	}
}

void DirectiveParser::parseElif(Token *token)
{
	assert(getDirective(token) == DIRECTIVE_ELIF);

	if (mConditionalStack.empty())
	{
		mDiagnostics->report(Diagnostics::PP_CONDITIONAL_ELIF_WITHOUT_IF,
		                     token->location, token->text);
		skipUntilEOD(mTokenizer, token);
		return;
	}

	ConditionalBlock &block = mConditionalStack.back();
	if (block.skipBlock)
	{
		// No diagnostics. Just skip the whole line.
		skipUntilEOD(mTokenizer, token);
		return;
	}
	if (block.foundElseGroup)
	{
		mDiagnostics->report(Diagnostics::PP_CONDITIONAL_ELIF_AFTER_ELSE,
		                     token->location, token->text);
		skipUntilEOD(mTokenizer, token);
		return;
	}
	if (block.foundValidGroup)
	{
		// Do not parse the expression.
		// Also be careful not to emit a diagnostic.
		block.skipGroup = true;
		skipUntilEOD(mTokenizer, token);
		return;
	}

	int expression = parseExpressionIf(token);
	block.skipGroup = expression == 0;
	block.foundValidGroup = expression != 0;
}

void DirectiveParser::parseEndif(Token *token)
{
	assert(getDirective(token) == DIRECTIVE_ENDIF);

	if (mConditionalStack.empty())
	{
		mDiagnostics->report(Diagnostics::PP_CONDITIONAL_ENDIF_WITHOUT_IF,
		                     token->location, token->text);
		skipUntilEOD(mTokenizer, token);
		return;
	}

	mConditionalStack.pop_back();

	// Check if there are tokens after #endif.
	mTokenizer->lex(token);
	if (!isEOD(token))
	{
		mDiagnostics->report(Diagnostics::PP_CONDITIONAL_UNEXPECTED_TOKEN,
		                     token->location, token->text);
		skipUntilEOD(mTokenizer, token);
	}
}

void DirectiveParser::parseError(Token *token)
{
	assert(getDirective(token) == DIRECTIVE_ERROR);

	std::ostringstream stream;
	mTokenizer->lex(token);
	while ((token->type != '\n') && (token->type != Token::LAST))
	{
		stream << *token;
		mTokenizer->lex(token);
	}
	mDirectiveHandler->handleError(token->location, stream.str());
}

// Parses pragma of form: #pragma name[(value)].
void DirectiveParser::parsePragma(Token *token)
{
	assert(getDirective(token) == DIRECTIVE_PRAGMA);

	enum State
	{
		PRAGMA_NAME,
		LEFT_PAREN,
		PRAGMA_VALUE,
		RIGHT_PAREN
	};

	bool valid = true;
	std::string name, value;
	int state = PRAGMA_NAME;

	mTokenizer->lex(token);
	bool stdgl = token->text == "STDGL";
	if (stdgl)
	{
		mTokenizer->lex(token);
	}
	while ((token->type != '\n') && (token->type != Token::LAST))
	{
		switch(state++)
		{
		case PRAGMA_NAME:
			name = token->text;
			valid = valid && (token->type == Token::IDENTIFIER);
			break;
		case LEFT_PAREN:
			valid = valid && (token->type == '(');
			break;
		case PRAGMA_VALUE:
			value = token->text;
			valid = valid && (token->type == Token::IDENTIFIER);
			break;
		case RIGHT_PAREN:
			valid = valid && (token->type == ')');
			break;
		default:
			valid = false;
			break;
		}
		mTokenizer->lex(token);
	}

	valid = valid && ((state == PRAGMA_NAME) ||     // Empty pragma.
	                  (state == LEFT_PAREN) ||      // Without value.
	                  (state == RIGHT_PAREN + 1));  // With value.
	if (!valid)
	{
		mDiagnostics->report(Diagnostics::PP_UNRECOGNIZED_PRAGMA, token->location, name);
	}
	else if (state > PRAGMA_NAME)  // Do not notify for empty pragma.
	{
		mDirectiveHandler->handlePragma(token->location, name, value, stdgl);
	}
}

void DirectiveParser::parseExtension(Token *token)
{
	assert(getDirective(token) == DIRECTIVE_EXTENSION);

	enum State
	{
		EXT_NAME,
		COLON,
		EXT_BEHAVIOR
	};

	bool valid = true;
	std::string name, behavior;
	int state = EXT_NAME;

	mTokenizer->lex(token);
	while ((token->type != '\n') && (token->type != Token::LAST))
	{
		switch (state++)
		{
			case EXT_NAME:
				if (valid && (token->type != Token::IDENTIFIER))
				{
					mDiagnostics->report(Diagnostics::PP_INVALID_EXTENSION_NAME, token->location,
					                     token->text);
					valid = false;
				}
				if (valid)
					name = token->text;
				break;
			case COLON:
				if (valid && (token->type != ':'))
				{
					mDiagnostics->report(Diagnostics::PP_UNEXPECTED_TOKEN, token->location,
					                     token->text);
					valid = false;
				}
				break;
			case EXT_BEHAVIOR:
				if (valid && (token->type != Token::IDENTIFIER))
				{
					mDiagnostics->report(Diagnostics::PP_INVALID_EXTENSION_BEHAVIOR,
					                     token->location, token->text);
					valid = false;
				}
				if (valid)
					behavior = token->text;
				break;
			default:
				if (valid)
				{
					mDiagnostics->report(Diagnostics::PP_UNEXPECTED_TOKEN, token->location,
					                     token->text);
					valid = false;
				}
				break;
		}
		mTokenizer->lex(token);
	}
	if (valid && (state != EXT_BEHAVIOR + 1))
	{
		mDiagnostics->report(Diagnostics::PP_INVALID_EXTENSION_DIRECTIVE, token->location,
		                     token->text);
		valid = false;
	}
	if (valid && mSeenNonPreprocessorToken)
	{
		if (mShaderVersion >= 300)
		{
			mDiagnostics->report(Diagnostics::PP_NON_PP_TOKEN_BEFORE_EXTENSION_ESSL3,
			                     token->location, token->text);
			valid = false;
		}
		else
		{
			mDiagnostics->report(Diagnostics::PP_NON_PP_TOKEN_BEFORE_EXTENSION_ESSL1,
			                     token->location, token->text);
		}
	}
	if (valid)
		mDirectiveHandler->handleExtension(token->location, name, behavior);
}

void DirectiveParser::parseVersion(Token *token)
{
	assert(getDirective(token) == DIRECTIVE_VERSION);

	if (mPastFirstStatement)
	{
		mDiagnostics->report(Diagnostics::PP_VERSION_NOT_FIRST_STATEMENT, token->location,
		                     token->text);
		skipUntilEOD(mTokenizer, token);
		return;
	}

	enum State
	{
		VERSION_NUMBER,
		VERSION_PROFILE,
		VERSION_ENDLINE
	};

	bool valid = true;
	int version = 0;
	int state = VERSION_NUMBER;

	mTokenizer->lex(token);
	while (valid && (token->type != '\n') && (token->type != Token::LAST))
	{
		switch (state)
		{
		case VERSION_NUMBER:
			if (token->type != Token::CONST_INT)
			{
				mDiagnostics->report(Diagnostics::PP_INVALID_VERSION_NUMBER,
				                     token->location, token->text);
				valid = false;
			}
			if (valid && !token->iValue(&version))
			{
				mDiagnostics->report(Diagnostics::PP_INTEGER_OVERFLOW,
				                     token->location, token->text);
				valid = false;
			}
			if (valid)
			{
				state = (version < 300) ? VERSION_ENDLINE : VERSION_PROFILE;
			}
			break;
		case VERSION_PROFILE:
			if (token->type != Token::IDENTIFIER || token->text != "es")
			{
				mDiagnostics->report(Diagnostics::PP_INVALID_VERSION_DIRECTIVE,
				                     token->location, token->text);
				valid = false;
			}
			state = VERSION_ENDLINE;
			break;
		default:
			mDiagnostics->report(Diagnostics::PP_UNEXPECTED_TOKEN,
			                     token->location, token->text);
			valid = false;
			break;
		}

		mTokenizer->lex(token);
	}

	if (valid && (state != VERSION_ENDLINE))
	{
		mDiagnostics->report(Diagnostics::PP_INVALID_VERSION_DIRECTIVE,
		                     token->location, token->text);
		valid = false;
	}

	if (valid && version >= 300 && token->location.line > 1)
	{
		mDiagnostics->report(Diagnostics::PP_VERSION_NOT_FIRST_LINE_ESSL3, token->location,
		                     token->text);
		valid = false;
	}

	if (valid)
	{
		mDirectiveHandler->handleVersion(token->location, version);
		mShaderVersion = version;
		PredefineMacro(mMacroSet, "__VERSION__", version);
	}
}

void DirectiveParser::parseLine(Token *token)
{
	assert(getDirective(token) == DIRECTIVE_LINE);

	bool valid = true;
	bool parsedFileNumber = false;
	int line = 0, file = 0;

	MacroExpander macroExpander(mTokenizer, mMacroSet, mDiagnostics, false, mMaxMacroExpansionDepth);

	// Lex the first token after "#line" so we can check it for EOD.
	macroExpander.lex(token);

	if (isEOD(token))
	{
		mDiagnostics->report(Diagnostics::PP_INVALID_LINE_DIRECTIVE, token->location, token->text);
		valid = false;
	}
	else
	{
		ExpressionParser expressionParser(&macroExpander, mDiagnostics);
		ExpressionParser::ErrorSettings errorSettings;

		// See GLES3 section 12.42
		errorSettings.integerLiteralsMustFit32BitSignedRange = true;

		errorSettings.unexpectedIdentifier = Diagnostics::PP_INVALID_LINE_NUMBER;
		// The first token was lexed earlier to check if it was EOD. Include
		// the token in parsing for a second time by setting the
		// parsePresetToken flag to true.
		expressionParser.parse(token, &line, true, errorSettings, &valid);
		if (!isEOD(token) && valid)
		{
			errorSettings.unexpectedIdentifier = Diagnostics::PP_INVALID_FILE_NUMBER;
			// After parsing the line expression expressionParser has also
			// advanced to the first token of the file expression - this is the
			// token that makes the parser reduce the "input" rule for the line
			// expression and stop. So we're using parsePresetToken = true here
			// as well.
			expressionParser.parse(token, &file, true, errorSettings, &valid);
			parsedFileNumber = true;
		}
		if (!isEOD(token))
		{
			if (valid)
			{
				mDiagnostics->report(Diagnostics::PP_UNEXPECTED_TOKEN,
				                     token->location, token->text);
				valid = false;
			}
			skipUntilEOD(mTokenizer, token);
		}
	}

	if (valid)
	{
		mTokenizer->setLineNumber(line);
		if (parsedFileNumber)
			mTokenizer->setFileNumber(file);
	}
}

bool DirectiveParser::skipping() const
{
	if (mConditionalStack.empty())
		return false;

	const ConditionalBlock &block = mConditionalStack.back();
	return block.skipBlock || block.skipGroup;
}

void DirectiveParser::parseConditionalIf(Token *token)
{
	ConditionalBlock block;
	block.type = token->text;
	block.location = token->location;

	if (skipping())
	{
		// This conditional block is inside another conditional group
		// which is skipped. As a consequence this whole block is skipped.
		// Be careful not to parse the conditional expression that might
		// emit a diagnostic.
		skipUntilEOD(mTokenizer, token);
		block.skipBlock = true;
	}
	else
	{
		DirectiveType directive = getDirective(token);

		int expression = 0;
		switch (directive)
		{
		case DIRECTIVE_IF:
			expression = parseExpressionIf(token);
			break;
		case DIRECTIVE_IFDEF:
			expression = parseExpressionIfdef(token);
			break;
		case DIRECTIVE_IFNDEF:
			expression = parseExpressionIfdef(token) == 0 ? 1 : 0;
			break;
		default:
			assert(false);
			break;
		}
		block.skipGroup = expression == 0;
		block.foundValidGroup = expression != 0;
	}
	mConditionalStack.push_back(block);
}

int DirectiveParser::parseExpressionIf(Token *token)
{
	assert((getDirective(token) == DIRECTIVE_IF) || (getDirective(token) == DIRECTIVE_ELIF));

	DefinedParser definedParser(mTokenizer, mMacroSet, mDiagnostics);
	MacroExpander macroExpander(&definedParser, mMacroSet, mDiagnostics, true, mMaxMacroExpansionDepth);
	ExpressionParser expressionParser(&macroExpander, mDiagnostics);

	int expression = 0;
	ExpressionParser::ErrorSettings errorSettings;
	errorSettings.integerLiteralsMustFit32BitSignedRange = false;
	errorSettings.unexpectedIdentifier = Diagnostics::PP_CONDITIONAL_UNEXPECTED_TOKEN;

	bool valid = true;
	expressionParser.parse(token, &expression, false, errorSettings, &valid);

	// Check if there are tokens after #if expression.
	if (!isEOD(token))
	{
		mDiagnostics->report(Diagnostics::PP_CONDITIONAL_UNEXPECTED_TOKEN,
		                     token->location, token->text);
		skipUntilEOD(mTokenizer, token);
	}

	return expression;
}

int DirectiveParser::parseExpressionIfdef(Token* token)
{
	assert((getDirective(token) == DIRECTIVE_IFDEF) ||
		   (getDirective(token) == DIRECTIVE_IFNDEF));

	mTokenizer->lex(token);
	if (token->type != Token::IDENTIFIER)
	{
		mDiagnostics->report(Diagnostics::PP_UNEXPECTED_TOKEN,
		                     token->location, token->text);
		skipUntilEOD(mTokenizer, token);
		return 0;
	}

	MacroSet::const_iterator iter = mMacroSet->find(token->text);
	int expression = iter != mMacroSet->end() ? 1 : 0;

	// Check if there are tokens after #ifdef expression.
	mTokenizer->lex(token);
	if (!isEOD(token))
	{
		mDiagnostics->report(Diagnostics::PP_CONDITIONAL_UNEXPECTED_TOKEN,
		                     token->location, token->text);
		skipUntilEOD(mTokenizer, token);
	}
	return expression;
}

}  // namespace pp