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1 //===--- MultipleIncludeOpt.h - Header Multiple-Include Optzn ---*- C++ -*-===//
2 //
3 //                     The LLVM Compiler Infrastructure
4 //
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
7 //
8 //===----------------------------------------------------------------------===//
9 ///
10 /// \file
11 /// \brief Defines the MultipleIncludeOpt interface.
12 //
13 //===----------------------------------------------------------------------===//
14 
15 #ifndef LLVM_CLANG_LEX_MULTIPLEINCLUDEOPT_H
16 #define LLVM_CLANG_LEX_MULTIPLEINCLUDEOPT_H
17 
18 #include "clang/Basic/SourceLocation.h"
19 
20 namespace clang {
21 class IdentifierInfo;
22 
23 /// \brief Implements the simple state machine that the Lexer class uses to
24 /// detect files subject to the 'multiple-include' optimization.
25 ///
26 /// The public methods in this class are triggered by various
27 /// events that occur when a file is lexed, and after the entire file is lexed,
28 /// information about which macro (if any) controls the header is returned.
29 class MultipleIncludeOpt {
30   /// ReadAnyTokens - This is set to false when a file is first opened and true
31   /// any time a token is returned to the client or a (non-multiple-include)
32   /// directive is parsed.  When the final \#endif is parsed this is reset back
33   /// to false, that way any tokens before the first \#ifdef or after the last
34   /// \#endif can be easily detected.
35   bool ReadAnyTokens;
36 
37   /// ImmediatelyAfterTopLevelIfndef - This is true when the only tokens
38   /// processed in the file so far is an #ifndef and an identifier.  Used in
39   /// the detection of header guards in a file.
40   bool ImmediatelyAfterTopLevelIfndef;
41 
42   /// ReadAnyTokens - This is set to false when a file is first opened and true
43   /// any time a token is returned to the client or a (non-multiple-include)
44   /// directive is parsed.  When the final #endif is parsed this is reset back
45   /// to false, that way any tokens before the first #ifdef or after the last
46   /// #endif can be easily detected.
47   bool DidMacroExpansion;
48 
49   /// TheMacro - The controlling macro for a file, if valid.
50   ///
51   const IdentifierInfo *TheMacro;
52 
53   /// DefinedMacro - The macro defined right after TheMacro, if any.
54   const IdentifierInfo *DefinedMacro;
55 
56   SourceLocation MacroLoc;
57   SourceLocation DefinedLoc;
58 public:
MultipleIncludeOpt()59   MultipleIncludeOpt() {
60     ReadAnyTokens = false;
61     ImmediatelyAfterTopLevelIfndef = false;
62     DidMacroExpansion = false;
63     TheMacro = nullptr;
64     DefinedMacro = nullptr;
65   }
66 
GetMacroLocation()67   SourceLocation GetMacroLocation() const {
68     return MacroLoc;
69   }
70 
GetDefinedLocation()71   SourceLocation GetDefinedLocation() const {
72     return DefinedLoc;
73   }
74 
resetImmediatelyAfterTopLevelIfndef()75   void resetImmediatelyAfterTopLevelIfndef() {
76     ImmediatelyAfterTopLevelIfndef = false;
77   }
78 
SetDefinedMacro(IdentifierInfo * M,SourceLocation Loc)79   void SetDefinedMacro(IdentifierInfo *M, SourceLocation Loc) {
80     DefinedMacro = M;
81     DefinedLoc = Loc;
82   }
83 
84   /// Invalidate - Permanently mark this file as not being suitable for the
85   /// include-file optimization.
Invalidate()86   void Invalidate() {
87     // If we have read tokens but have no controlling macro, the state-machine
88     // below can never "accept".
89     ReadAnyTokens = true;
90     ImmediatelyAfterTopLevelIfndef = false;
91     DefinedMacro = nullptr;
92     TheMacro = nullptr;
93   }
94 
95   /// getHasReadAnyTokensVal - This is used for the \#ifndef hande-shake at the
96   /// top of the file when reading preprocessor directives.  Otherwise, reading
97   /// the "ifndef x" would count as reading tokens.
getHasReadAnyTokensVal()98   bool getHasReadAnyTokensVal() const { return ReadAnyTokens; }
99 
100   /// getImmediatelyAfterTopLevelIfndef - returns true if the last directive
101   /// was an #ifndef at the beginning of the file.
getImmediatelyAfterTopLevelIfndef()102   bool getImmediatelyAfterTopLevelIfndef() const {
103     return ImmediatelyAfterTopLevelIfndef;
104   }
105 
106   // If a token is read, remember that we have seen a side-effect in this file.
ReadToken()107   void ReadToken() {
108     ReadAnyTokens = true;
109     ImmediatelyAfterTopLevelIfndef = false;
110   }
111 
112   /// ExpandedMacro - When a macro is expanded with this lexer as the current
113   /// buffer, this method is called to disable the MIOpt if needed.
ExpandedMacro()114   void ExpandedMacro() { DidMacroExpansion = true; }
115 
116   /// \brief Called when entering a top-level \#ifndef directive (or the
117   /// "\#if !defined" equivalent) without any preceding tokens.
118   ///
119   /// Note, we don't care about the input value of 'ReadAnyTokens'.  The caller
120   /// ensures that this is only called if there are no tokens read before the
121   /// \#ifndef.  The caller is required to do this, because reading the \#if
122   /// line obviously reads in in tokens.
EnterTopLevelIfndef(const IdentifierInfo * M,SourceLocation Loc)123   void EnterTopLevelIfndef(const IdentifierInfo *M, SourceLocation Loc) {
124     // If the macro is already set, this is after the top-level #endif.
125     if (TheMacro)
126       return Invalidate();
127 
128     // If we have already expanded a macro by the end of the #ifndef line, then
129     // there is a macro expansion *in* the #ifndef line.  This means that the
130     // condition could evaluate differently when subsequently #included.  Reject
131     // this.
132     if (DidMacroExpansion)
133       return Invalidate();
134 
135     // Remember that we're in the #if and that we have the macro.
136     ReadAnyTokens = true;
137     ImmediatelyAfterTopLevelIfndef = true;
138     TheMacro = M;
139     MacroLoc = Loc;
140   }
141 
142   /// \brief Invoked when a top level conditional (except \#ifndef) is found.
EnterTopLevelConditional()143   void EnterTopLevelConditional() {
144     // If a conditional directive (except #ifndef) is found at the top level,
145     // there is a chunk of the file not guarded by the controlling macro.
146     Invalidate();
147   }
148 
149   /// \brief Called when the lexer exits the top-level conditional.
ExitTopLevelConditional()150   void ExitTopLevelConditional() {
151     // If we have a macro, that means the top of the file was ok.  Set our state
152     // back to "not having read any tokens" so we can detect anything after the
153     // #endif.
154     if (!TheMacro) return Invalidate();
155 
156     // At this point, we haven't "read any tokens" but we do have a controlling
157     // macro.
158     ReadAnyTokens = false;
159     ImmediatelyAfterTopLevelIfndef = false;
160   }
161 
162   /// \brief Once the entire file has been lexed, if there is a controlling
163   /// macro, return it.
GetControllingMacroAtEndOfFile()164   const IdentifierInfo *GetControllingMacroAtEndOfFile() const {
165     // If we haven't read any tokens after the #endif, return the controlling
166     // macro if it's valid (if it isn't, it will be null).
167     if (!ReadAnyTokens)
168       return TheMacro;
169     return nullptr;
170   }
171 
172   /// \brief If the ControllingMacro is followed by a macro definition, return
173   /// the macro that was defined.
GetDefinedMacro()174   const IdentifierInfo *GetDefinedMacro() const {
175     return DefinedMacro;
176   }
177 };
178 
179 }  // end namespace clang
180 
181 #endif
182