1 //===-- lib/Parser/preprocessor.h -------------------------------*- C++ -*-===//
2 //
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
6 //
7 //===----------------------------------------------------------------------===//
8 
9 #ifndef FORTRAN_PARSER_PREPROCESSOR_H_
10 #define FORTRAN_PARSER_PREPROCESSOR_H_
11 
12 // A Fortran-aware preprocessing module used by the prescanner to implement
13 // preprocessing directives and macro replacement.  Intended to be efficient
14 // enough to always run on all source files even when no preprocessing is
15 // performed, so that special compiler command options &/or source file name
16 // extensions for preprocessing will not be necessary.
17 
18 #include "token-sequence.h"
19 #include "flang/Parser/char-block.h"
20 #include "flang/Parser/provenance.h"
21 #include <cstddef>
22 #include <list>
23 #include <stack>
24 #include <string>
25 #include <unordered_map>
26 #include <vector>
27 
28 namespace Fortran::parser {
29 
30 class Prescanner;
31 class Preprocessor;
32 
33 // Defines a macro
34 class Definition {
35 public:
36   Definition(const TokenSequence &, std::size_t firstToken, std::size_t tokens);
37   Definition(const std::vector<std::string> &argNames, const TokenSequence &,
38       std::size_t firstToken, std::size_t tokens, bool isVariadic = false);
39   Definition(const std::string &predefined, AllSources &);
40 
isFunctionLike()41   bool isFunctionLike() const { return isFunctionLike_; }
argumentCount()42   std::size_t argumentCount() const { return argumentCount_; }
isVariadic()43   bool isVariadic() const { return isVariadic_; }
isDisabled()44   bool isDisabled() const { return isDisabled_; }
isPredefined()45   bool isPredefined() const { return isPredefined_; }
replacement()46   const TokenSequence &replacement() const { return replacement_; }
47 
48   bool set_isDisabled(bool disable);
49 
50   TokenSequence Apply(const std::vector<TokenSequence> &args, Prescanner &);
51 
52 private:
53   static TokenSequence Tokenize(const std::vector<std::string> &argNames,
54       const TokenSequence &token, std::size_t firstToken, std::size_t tokens);
55 
56   bool isFunctionLike_{false};
57   std::size_t argumentCount_{0};
58   bool isVariadic_{false};
59   bool isDisabled_{false};
60   bool isPredefined_{false};
61   TokenSequence replacement_;
62 };
63 
64 // Preprocessing state
65 class Preprocessor {
66 public:
67   explicit Preprocessor(AllSources &);
68 
allSources()69   const AllSources &allSources() const { return allSources_; }
allSources()70   AllSources &allSources() { return allSources_; }
71 
72   void DefineStandardMacros();
73   void Define(std::string macro, std::string value);
74   void Undefine(std::string macro);
75   bool IsNameDefined(const CharBlock &);
76 
77   std::optional<TokenSequence> MacroReplacement(
78       const TokenSequence &, Prescanner &);
79 
80   // Implements a preprocessor directive.
81   void Directive(const TokenSequence &, Prescanner &);
82 
83 private:
84   enum class IsElseActive { No, Yes };
85   enum class CanDeadElseAppear { No, Yes };
86 
87   CharBlock SaveTokenAsName(const CharBlock &);
88   TokenSequence ReplaceMacros(const TokenSequence &, Prescanner &);
89   void SkipDisabledConditionalCode(
90       const std::string &, IsElseActive, Prescanner &, ProvenanceRange);
91   bool IsIfPredicateTrue(const TokenSequence &expr, std::size_t first,
92       std::size_t exprTokens, Prescanner &);
93 
94   AllSources &allSources_;
95   std::list<std::string> names_;
96   std::unordered_map<CharBlock, Definition> definitions_;
97   std::stack<CanDeadElseAppear> ifStack_;
98 };
99 } // namespace Fortran::parser
100 #endif // FORTRAN_PARSER_PREPROCESSOR_H_
101