1 //===- VariadicMacroSupport.h - state machines and scope guards -*- C++ -*-===//
3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4 // See https://llvm.org/LICENSE.txt for license information.
5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
7 //===----------------------------------------------------------------------===//
9 // This file defines support types to help with preprocessing variadic macro
10 // (i.e. macros that use: ellipses __VA_ARGS__ ) definitions and
13 //===----------------------------------------------------------------------===//
15 #ifndef LLVM_CLANG_LEX_VARIADICMACROSUPPORT_H
16 #define LLVM_CLANG_LEX_VARIADICMACROSUPPORT_H
18 #include "clang/Lex/Preprocessor.h"
19 #include "llvm/ADT/SmallVector.h"
24 /// An RAII class that tracks when the Preprocessor starts and stops lexing
25 /// the definition of a (ISO C/C++) variadic macro. As an example, this is
26 /// useful for unpoisoning and repoisoning certain identifiers (such as
27 /// __VA_ARGS__) that are only allowed in this context. Also, being a friend
28 /// of the Preprocessor class allows it to access PP's cached identifiers
29 /// directly (as opposed to performing a lookup each time).
30 class VariadicMacroScopeGuard {
31 const Preprocessor &PP;
32 IdentifierInfo *const Ident__VA_ARGS__;
33 IdentifierInfo *const Ident__VA_OPT__;
36 VariadicMacroScopeGuard(const Preprocessor &P)
37 : PP(P), Ident__VA_ARGS__(PP.Ident__VA_ARGS__),
38 Ident__VA_OPT__(PP.Ident__VA_OPT__) {
39 assert(Ident__VA_ARGS__->isPoisoned() && "__VA_ARGS__ should be poisoned "
40 "outside an ISO C/C++ variadic "
44 (Ident__VA_OPT__->isPoisoned() && "__VA_OPT__ should be poisoned!"));
47 /// Client code should call this function just before the Preprocessor is
48 /// about to Lex tokens from the definition of a variadic (ISO C/C++) macro.
50 Ident__VA_ARGS__->setIsPoisoned(false);
52 Ident__VA_OPT__->setIsPoisoned(false);
55 /// Client code should call this function as soon as the Preprocessor has
56 /// either completed lexing the macro's definition tokens, or an error
57 /// occurred and the context is being exited. This function is idempotent
58 /// (might be explicitly called, and then reinvoked via the destructor).
60 Ident__VA_ARGS__->setIsPoisoned(true);
62 Ident__VA_OPT__->setIsPoisoned(true);
65 ~VariadicMacroScopeGuard() { exitScope(); }
68 /// A class for tracking whether we're inside a VA_OPT during a
69 /// traversal of the tokens of a variadic macro definition.
70 class VAOptDefinitionContext {
71 /// Contains all the locations of so far unmatched lparens.
72 SmallVector<SourceLocation, 8> UnmatchedOpeningParens;
74 const IdentifierInfo *const Ident__VA_OPT__;
78 VAOptDefinitionContext(Preprocessor &PP)
79 : Ident__VA_OPT__(PP.Ident__VA_OPT__) {}
81 bool isVAOptToken(const Token &T) const {
82 return Ident__VA_OPT__ && T.getIdentifierInfo() == Ident__VA_OPT__;
85 /// Returns true if we have seen the __VA_OPT__ and '(' but before having
86 /// seen the matching ')'.
87 bool isInVAOpt() const { return UnmatchedOpeningParens.size(); }
89 /// Call this function as soon as you see __VA_OPT__ and '('.
90 void sawVAOptFollowedByOpeningParens(const SourceLocation LParenLoc) {
91 assert(!isInVAOpt() && "Must NOT be within VAOPT context to call this");
92 UnmatchedOpeningParens.push_back(LParenLoc);
96 SourceLocation getUnmatchedOpeningParenLoc() const {
97 assert(isInVAOpt() && "Must be within VAOPT context to call this");
98 return UnmatchedOpeningParens.back();
101 /// Call this function each time an rparen is seen. It returns true only if
102 /// the rparen that was just seen was the eventual (non-nested) closing
103 /// paren for VAOPT, and ejects us out of the VAOPT context.
104 bool sawClosingParen() {
105 assert(isInVAOpt() && "Must be within VAOPT context to call this");
106 UnmatchedOpeningParens.pop_back();
107 return !UnmatchedOpeningParens.size();
110 /// Call this function each time an lparen is seen.
111 void sawOpeningParen(SourceLocation LParenLoc) {
112 assert(isInVAOpt() && "Must be within VAOPT context to call this");
113 UnmatchedOpeningParens.push_back(LParenLoc);
116 /// Are we at the top level within the __VA_OPT__?
117 bool isAtTopLevel() const { return UnmatchedOpeningParens.size() == 1; }
120 /// A class for tracking whether we're inside a VA_OPT during a
121 /// traversal of the tokens of a macro during macro expansion.
122 class VAOptExpansionContext : VAOptDefinitionContext {
124 Token SyntheticEOFToken;
126 // The (spelling) location of the current __VA_OPT__ in the replacement list
127 // of the function-like macro being expanded.
128 SourceLocation VAOptLoc;
130 // NumOfTokensPriorToVAOpt : when != -1, contains the index *of* the first
131 // token of the current VAOPT contents (so we know where to start eager
132 // token-pasting and stringification) *within* the substituted tokens of
133 // the function-like macro's new replacement list.
134 int NumOfTokensPriorToVAOpt = -1;
136 unsigned LeadingSpaceForStringifiedToken : 1;
138 unsigned StringifyBefore : 1;
139 unsigned CharifyBefore : 1;
140 unsigned BeginsWithPlaceholder : 1;
141 unsigned EndsWithPlaceholder : 1;
143 bool hasStringifyBefore() const {
145 "Must only be called if the state has not been reset");
146 return StringifyBefore;
149 bool isReset() const {
150 return NumOfTokensPriorToVAOpt == -1 ||
151 VAOptLoc.isInvalid();
155 VAOptExpansionContext(Preprocessor &PP)
156 : VAOptDefinitionContext(PP), LeadingSpaceForStringifiedToken(false),
157 StringifyBefore(false), CharifyBefore(false),
158 BeginsWithPlaceholder(false), EndsWithPlaceholder(false) {
159 SyntheticEOFToken.startToken();
160 SyntheticEOFToken.setKind(tok::eof);
164 VAOptLoc = SourceLocation();
165 NumOfTokensPriorToVAOpt = -1;
166 LeadingSpaceForStringifiedToken = false;
167 StringifyBefore = false;
168 CharifyBefore = false;
169 BeginsWithPlaceholder = false;
170 EndsWithPlaceholder = false;
173 const Token &getEOFTok() const { return SyntheticEOFToken; }
175 void sawHashOrHashAtBefore(const bool HasLeadingSpace,
176 const bool IsHashAt) {
178 StringifyBefore = !IsHashAt;
179 CharifyBefore = IsHashAt;
180 LeadingSpaceForStringifiedToken = HasLeadingSpace;
183 void hasPlaceholderAfterHashhashAtStart() { BeginsWithPlaceholder = true; }
184 void hasPlaceholderBeforeRParen() {
186 EndsWithPlaceholder = true;
190 bool beginsWithPlaceholder() const {
192 "Must only be called if the state has not been reset");
193 return BeginsWithPlaceholder;
195 bool endsWithPlaceholder() const {
197 "Must only be called if the state has not been reset");
198 return EndsWithPlaceholder;
201 bool hasCharifyBefore() const {
203 "Must only be called if the state has not been reset");
204 return CharifyBefore;
206 bool hasStringifyOrCharifyBefore() const {
207 return hasStringifyBefore() || hasCharifyBefore();
210 unsigned int getNumberOfTokensPriorToVAOpt() const {
212 "Must only be called if the state has not been reset");
213 return NumOfTokensPriorToVAOpt;
216 bool getLeadingSpaceForStringifiedToken() const {
217 assert(hasStringifyBefore() &&
218 "Must only be called if this has been marked for stringification");
219 return LeadingSpaceForStringifiedToken;
222 void sawVAOptFollowedByOpeningParens(const SourceLocation VAOptLoc,
223 const unsigned int NumPriorTokens) {
224 assert(VAOptLoc.isFileID() && "Must not come from a macro expansion");
225 assert(isReset() && "Must only be called if the state has been reset");
226 VAOptDefinitionContext::sawVAOptFollowedByOpeningParens(SourceLocation());
227 this->VAOptLoc = VAOptLoc;
228 NumOfTokensPriorToVAOpt = NumPriorTokens;
229 assert(NumOfTokensPriorToVAOpt > -1 &&
230 "Too many prior tokens");
233 SourceLocation getVAOptLoc() const {
235 "Must only be called if the state has not been reset");
236 assert(VAOptLoc.isValid() && "__VA_OPT__ location must be valid");
239 using VAOptDefinitionContext::isVAOptToken;
240 using VAOptDefinitionContext::isInVAOpt;
241 using VAOptDefinitionContext::sawClosingParen;
242 using VAOptDefinitionContext::sawOpeningParen;
245 } // end namespace clang