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//===--- TokenLexer.cpp - Lex from a token stream -------------------------===//
// The LLVM Compiler Infrastructure
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
// This file implements the TokenLexer interface.
#include "clang/Lex/TokenLexer.h"
#include "MacroArgs.h"
#include "clang/Lex/MacroInfo.h"
#include "clang/Lex/Preprocessor.h"
#include "clang/Basic/SourceManager.h"
#include "clang/Lex/LexDiagnostic.h"
#include "llvm/ADT/SmallVector.h"
using namespace clang;
/// Create a TokenLexer for the specified macro with the specified actual
/// arguments. Note that this ctor takes ownership of the ActualArgs pointer.
void TokenLexer::Init(Token &Tok, SourceLocation ILEnd, MacroArgs *Actuals) {
// If the client is reusing a TokenLexer, make sure to free any memory
// associated with it.
Macro = PP.getMacroInfo(Tok.getIdentifierInfo());
ActualArgs = Actuals;
CurToken = 0;
InstantiateLocStart = Tok.getLocation();
InstantiateLocEnd = ILEnd;
AtStartOfLine = Tok.isAtStartOfLine();
HasLeadingSpace = Tok.hasLeadingSpace();
Tokens = &*Macro->tokens_begin();
OwnsTokens = false;
DisableMacroExpansion = false;
NumTokens = Macro->tokens_end()-Macro->tokens_begin();
// If this is a function-like macro, expand the arguments and change
// Tokens to point to the expanded tokens.
if (Macro->isFunctionLike() && Macro->getNumArgs())
// Mark the macro as currently disabled, so that it is not recursively
// expanded. The macro must be disabled only after argument pre-expansion of
// function-like macro arguments occurs.
/// Create a TokenLexer for the specified token stream. This does not
/// take ownership of the specified token vector.
void TokenLexer::Init(const Token *TokArray, unsigned NumToks,
bool disableMacroExpansion, bool ownsTokens) {
// If the client is reusing a TokenLexer, make sure to free any memory
// associated with it.
Macro = 0;
ActualArgs = 0;
Tokens = TokArray;
OwnsTokens = ownsTokens;
DisableMacroExpansion = disableMacroExpansion;
NumTokens = NumToks;
CurToken = 0;
InstantiateLocStart = InstantiateLocEnd = SourceLocation();
AtStartOfLine = false;
HasLeadingSpace = false;
// Set HasLeadingSpace/AtStartOfLine so that the first token will be
// returned unmodified.
if (NumToks != 0) {
AtStartOfLine = TokArray[0].isAtStartOfLine();
HasLeadingSpace = TokArray[0].hasLeadingSpace();
void TokenLexer::destroy() {
// If this was a function-like macro that actually uses its arguments, delete
// the expanded tokens.
if (OwnsTokens) {
delete [] Tokens;
Tokens = 0;
OwnsTokens = false;
// TokenLexer owns its formal arguments.
if (ActualArgs) ActualArgs->destroy();
/// Expand the arguments of a function-like macro so that we can quickly
/// return preexpanded tokens from Tokens.
void TokenLexer::ExpandFunctionArguments() {
llvm::SmallVector<Token, 128> ResultToks;
// Loop through 'Tokens', expanding them into ResultToks. Keep
// track of whether we change anything. If not, no need to keep them. If so,
// we install the newly expanded sequence as the new 'Tokens' list.
bool MadeChange = false;
// NextTokGetsSpace - When this is true, the next token appended to the
// output list will get a leading space, regardless of whether it had one to
// begin with or not. This is used for placemarker support.
bool NextTokGetsSpace = false;
for (unsigned i = 0, e = NumTokens; i != e; ++i) {
// If we found the stringify operator, get the argument stringified. The
// preprocessor already verified that the following token is a macro name
// when the #define was parsed.
const Token &CurTok = Tokens[i];
if ( || {
int ArgNo = Macro->getArgumentNum(Tokens[i+1].getIdentifierInfo());
assert(ArgNo != -1 && "Token following # is not an argument?");
Token Res;
if ( // Stringify
Res = ActualArgs->getStringifiedArgument(ArgNo, PP);
else {
// 'charify': don't bother caching these.
Res = MacroArgs::StringifyArgument(ActualArgs->getUnexpArgument(ArgNo),
PP, true);
// The stringified/charified string leading space flag gets set to match
// the #/#@ operator.
if (CurTok.hasLeadingSpace() || NextTokGetsSpace)
MadeChange = true;
++i; // Skip arg name.
NextTokGetsSpace = false;
// Otherwise, if this is not an argument token, just add the token to the
// output buffer.
IdentifierInfo *II = CurTok.getIdentifierInfo();
int ArgNo = II ? Macro->getArgumentNum(II) : -1;
if (ArgNo == -1) {
// This isn't an argument, just add it.
if (NextTokGetsSpace) {
NextTokGetsSpace = false;
// An argument is expanded somehow, the result is different than the
// input.
MadeChange = true;
// Otherwise, this is a use of the argument. Find out if there is a paste
// (##) operator before or after the argument.
bool PasteBefore =
!ResultToks.empty() && ResultToks.back().is(tok::hashhash);
bool PasteAfter = i+1 != e && Tokens[i+1].is(tok::hashhash);
// If it is not the LHS/RHS of a ## operator, we must pre-expand the
// argument and substitute the expanded tokens into the result. This is
// C99
if (!PasteBefore && !PasteAfter) {
const Token *ResultArgToks;
// Only preexpand the argument if it could possibly need it. This
// avoids some work in common cases.
const Token *ArgTok = ActualArgs->getUnexpArgument(ArgNo);
if (ActualArgs->ArgNeedsPreexpansion(ArgTok, PP))
ResultArgToks = &ActualArgs->getPreExpArgument(ArgNo, PP)[0];
ResultArgToks = ArgTok; // Use non-preexpanded tokens.
// If the arg token expanded into anything, append it.
if (ResultArgToks->isNot(tok::eof)) {
unsigned FirstResult = ResultToks.size();
unsigned NumToks = MacroArgs::getArgLength(ResultArgToks);
ResultToks.append(ResultArgToks, ResultArgToks+NumToks);
// If any tokens were substituted from the argument, the whitespace
// before the first token should match the whitespace of the arg
// identifier.
CurTok.hasLeadingSpace() ||
NextTokGetsSpace = false;
} else {
// If this is an empty argument, and if there was whitespace before the
// formal token, make sure the next token gets whitespace before it.
NextTokGetsSpace = CurTok.hasLeadingSpace();
// Okay, we have a token that is either the LHS or RHS of a paste (##)
// argument. It gets substituted as its non-pre-expanded tokens.
const Token *ArgToks = ActualArgs->getUnexpArgument(ArgNo);
unsigned NumToks = MacroArgs::getArgLength(ArgToks);
if (NumToks) { // Not an empty argument?
// If this is the GNU ", ## __VA_ARG__" extension, and we just learned
// that __VA_ARG__ expands to multiple tokens, avoid a pasting error when
// the expander trys to paste ',' with the first token of the __VA_ARG__
// expansion.
if (PasteBefore && ResultToks.size() >= 2 &&
ResultToks[ResultToks.size()-2].is(tok::comma) &&
(unsigned)ArgNo == Macro->getNumArgs()-1 &&
Macro->isVariadic()) {
// Remove the paste operator, report use of the extension.
PP.Diag(ResultToks.back().getLocation(), diag::ext_paste_comma);
ResultToks.append(ArgToks, ArgToks+NumToks);
// If this token (the macro argument) was supposed to get leading
// whitespace, transfer this information onto the first token of the
// expansion.
// Do not do this if the paste operator occurs before the macro argument,
// as in "A ## MACROARG". In valid code, the first token will get
// smooshed onto the preceding one anyway (forming AMACROARG). In
// assembler-with-cpp mode, invalid pastes are allowed through: in this
// case, we do not want the extra whitespace to be added. For example,
// we want ". ## foo" -> ".foo" not ". foo".
if ((CurTok.hasLeadingSpace() || NextTokGetsSpace) &&
NextTokGetsSpace = false;
// If an empty argument is on the LHS or RHS of a paste, the standard (C99
//,3) calls for a bunch of placemarker stuff to occur. We
// implement this by eating ## operators when a LHS or RHS expands to
// empty.
NextTokGetsSpace |= CurTok.hasLeadingSpace();
if (PasteAfter) {
// Discard the argument token and skip (don't copy to the expansion
// buffer) the paste operator after it.
NextTokGetsSpace |= Tokens[i+1].hasLeadingSpace();
// If this is on the RHS of a paste operator, we've already copied the
// paste operator to the ResultToks list. Remove it.
assert(PasteBefore && ResultToks.back().is(tok::hashhash));
NextTokGetsSpace |= ResultToks.back().hasLeadingSpace();
// If this is the __VA_ARGS__ token, and if the argument wasn't provided,
// and if the macro had at least one real argument, and if the token before
// the ## was a comma, remove the comma.
if ((unsigned)ArgNo == Macro->getNumArgs()-1 && // is __VA_ARGS__
ActualArgs->isVarargsElidedUse() && // Argument elided.
!ResultToks.empty() && ResultToks.back().is(tok::comma)) {
// Never add a space, even if the comma, ##, or arg had a space.
NextTokGetsSpace = false;
// Remove the paste operator, report use of the extension.
PP.Diag(ResultToks.back().getLocation(), diag::ext_paste_comma);
// If anything changed, install this as the new Tokens list.
if (MadeChange) {
assert(!OwnsTokens && "This would leak if we already own the token list");
// This is deleted in the dtor.
NumTokens = ResultToks.size();
llvm::BumpPtrAllocator &Alloc = PP.getPreprocessorAllocator();
Token *Res =
static_cast<Token *>(Alloc.Allocate(sizeof(Token)*ResultToks.size(),
if (NumTokens)
memcpy(Res, &ResultToks[0], NumTokens*sizeof(Token));
Tokens = Res;
// The preprocessor bump pointer owns these tokens, not us.
OwnsTokens = false;
/// Lex - Lex and return a token from this macro stream.
void TokenLexer::Lex(Token &Tok) {
// Lexing off the end of the macro, pop this macro off the expansion stack.
if (isAtEnd()) {
// If this is a macro (not a token stream), mark the macro enabled now
// that it is no longer being expanded.
if (Macro) Macro->EnableMacro();
// Pop this context off the preprocessors lexer stack and get the next
// token. This will delete "this" so remember the PP instance var.
Preprocessor &PPCache = PP;
if (PP.HandleEndOfTokenLexer(Tok))
// HandleEndOfTokenLexer may not return a token. If it doesn't, lex
// whatever is next.
return PPCache.Lex(Tok);
// If this is the first token of the expanded result, we inherit spacing
// properties later.
bool isFirstToken = CurToken == 0;
// Get the next token to return.
Tok = Tokens[CurToken++];
bool TokenIsFromPaste = false;
// If this token is followed by a token paste (##) operator, paste the tokens!
if (!isAtEnd() && Tokens[CurToken].is(tok::hashhash)) {
if (PasteTokens(Tok)) {
// When handling the microsoft /##/ extension, the final token is
// returned by PasteTokens, not the pasted token.
} else {
TokenIsFromPaste = true;
// The token's current location indicate where the token was lexed from. We
// need this information to compute the spelling of the token, but any
// diagnostics for the expanded token should appear as if they came from
// InstantiationLoc. Pull this information together into a new SourceLocation
// that captures all of this.
if (InstantiateLocStart.isValid()) { // Don't do this for token streams.
SourceManager &SM = PP.getSourceManager();
// If this is the first token, set the lexical properties of the token to
// match the lexical properties of the macro identifier.
if (isFirstToken) {
Tok.setFlagValue(Token::StartOfLine , AtStartOfLine);
Tok.setFlagValue(Token::LeadingSpace, HasLeadingSpace);
// Handle recursive expansion!
if (!Tok.isAnnotation() && Tok.getIdentifierInfo() != 0) {
// Change the kind of this identifier to the appropriate token kind, e.g.
// turning "for" into a keyword.
IdentifierInfo *II = Tok.getIdentifierInfo();
// If this identifier was poisoned and from a paste, emit an error. This
// won't be handled by Preprocessor::HandleIdentifier because this is coming
// from a macro expansion.
if (II->isPoisoned() && TokenIsFromPaste) {
// We warn about __VA_ARGS__ with poisoning.
if (II->isStr("__VA_ARGS__"))
PP.Diag(Tok, diag::ext_pp_bad_vaargs_use);
PP.Diag(Tok, diag::err_pp_used_poisoned_id);
if (!DisableMacroExpansion && II->isHandleIdentifierCase())
// Otherwise, return a normal token.
/// PasteTokens - Tok is the LHS of a ## operator, and CurToken is the ##
/// operator. Read the ## and RHS, and paste the LHS/RHS together. If there
/// are more ## after it, chomp them iteratively. Return the result as Tok.
/// If this returns true, the caller should immediately return the token.
bool TokenLexer::PasteTokens(Token &Tok) {
llvm::SmallVector<char, 128> Buffer;
const char *ResultTokStrPtr = 0;
do {
// Consume the ## operator.
SourceLocation PasteOpLoc = Tokens[CurToken].getLocation();
assert(!isAtEnd() && "No token on the RHS of a paste operator!");
// Get the RHS token.
const Token &RHS = Tokens[CurToken];
// Allocate space for the result token. This is guaranteed to be enough for
// the two tokens.
Buffer.resize(Tok.getLength() + RHS.getLength());
// Get the spelling of the LHS token in Buffer.
const char *BufPtr = &Buffer[0];
unsigned LHSLen = PP.getSpelling(Tok, BufPtr);
if (BufPtr != &Buffer[0]) // Really, we want the chars in Buffer!
memcpy(&Buffer[0], BufPtr, LHSLen);
BufPtr = &Buffer[LHSLen];
unsigned RHSLen = PP.getSpelling(RHS, BufPtr);
if (BufPtr != &Buffer[LHSLen]) // Really, we want the chars in Buffer!
memcpy(&Buffer[LHSLen], BufPtr, RHSLen);
// Trim excess space.
// Plop the pasted result (including the trailing newline and null) into a
// scratch buffer where we can lex it.
Token ResultTokTmp;
// Claim that the tmp token is a string_literal so that we can get the
// character pointer back from CreateString.
PP.CreateString(&Buffer[0], Buffer.size(), ResultTokTmp);
SourceLocation ResultTokLoc = ResultTokTmp.getLocation();
ResultTokStrPtr = ResultTokTmp.getLiteralData();
// Lex the resultant pasted token into Result.
Token Result;
if ( && {
// Common paste case: identifier+identifier = identifier. Avoid creating
// a lexer and other overhead.
} else {
assert(ResultTokLoc.isFileID() &&
"Should be a raw location into scratch buffer");
SourceManager &SourceMgr = PP.getSourceManager();
FileID LocFileID = SourceMgr.getFileID(ResultTokLoc);
const char *ScratchBufStart = SourceMgr.getBufferData(LocFileID).first;
// Make a lexer to lex this string from. Lex just this one token.
// Make a lexer object so that we lex and expand the paste result.
Lexer TL(SourceMgr.getLocForStartOfFile(LocFileID),
PP.getLangOptions(), ScratchBufStart,
ResultTokStrPtr, ResultTokStrPtr+LHSLen+RHSLen);
// Lex a token in raw mode. This way it won't look up identifiers
// automatically, lexing off the end will return an eof token, and
// warnings are disabled. This returns true if the result token is the
// entire buffer.
bool isInvalid = !TL.LexFromRawLexer(Result);
// If we got an EOF token, we didn't form even ONE token. For example, we
// did "/ ## /" to get "//".
isInvalid |=;
// If pasting the two tokens didn't form a full new token, this is an
// error. This occurs with "x ## +" and other stuff. Return with Tok
// unmodified and with RHS as the next token to lex.
if (isInvalid) {
// Test for the Microsoft extension of /##/ turning into // here on the
// error path.
if (PP.getLangOptions().Microsoft && && {
return true;
// Do not emit the warning when preprocessing assembler code.
if (!PP.getLangOptions().AsmPreprocessor) {
// Explicitly convert the token location to have proper instantiation
// information so that the user knows where it came from.
SourceManager &SM = PP.getSourceManager();
SourceLocation Loc =
SM.createInstantiationLoc(PasteOpLoc, InstantiateLocStart,
InstantiateLocEnd, 2);
PP.Diag(Loc, diag::err_pp_bad_paste)
<< std::string(Buffer.begin(), Buffer.end());
// Do not consume the RHS.
// Turn ## into 'unknown' to avoid # ## # from looking like a paste
// operator.
if (
// Transfer properties of the LHS over the the Result.
Result.setFlagValue(Token::StartOfLine , Tok.isAtStartOfLine());
Result.setFlagValue(Token::LeadingSpace, Tok.hasLeadingSpace());
// Finally, replace LHS with the result, consume the RHS, and iterate.
Tok = Result;
} while (!isAtEnd() && Tokens[CurToken].is(tok::hashhash));
// Now that we got the result token, it will be subject to expansion. Since
// token pasting re-lexes the result token in raw mode, identifier information
// isn't looked up. As such, if the result is an identifier, look up id info.
if ( {
// Look up the identifier info for the token. We disabled identifier lookup
// by saying we're skipping contents, so we need to do this manually.
IdentifierInfo *II = PP.LookUpIdentifierInfo(Tok, ResultTokStrPtr);
return false;
/// isNextTokenLParen - If the next token lexed will pop this macro off the
/// expansion stack, return 2. If the next unexpanded token is a '(', return
/// 1, otherwise return 0.
unsigned TokenLexer::isNextTokenLParen() const {
// Out of tokens?
if (isAtEnd())
return 2;
return Tokens[CurToken].is(tok::l_paren);
/// HandleMicrosoftCommentPaste - In microsoft compatibility mode, /##/ pastes
/// together to form a comment that comments out everything in the current
/// macro, other active macros, and anything left on the current physical
/// source line of the instantiated buffer. Handle this by returning the
/// first token on the next line.
void TokenLexer::HandleMicrosoftCommentPaste(Token &Tok) {
// We 'comment out' the rest of this macro by just ignoring the rest of the
// tokens that have not been lexed yet, if any.
// Since this must be a macro, mark the macro enabled now that it is no longer
// being expanded.
assert(Macro && "Token streams can't paste comments");