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 
32 // Defines a macro
33 class Definition {
34 public:
35   Definition(const TokenSequence &, std::size_t firstToken, std::size_t tokens);
36   Definition(const std::vector<std::string> &argNames, const TokenSequence &,
37       std::size_t firstToken, std::size_t tokens, bool isVariadic = false);
38   Definition(const std::string &predefined, AllSources &);
39 
40   bool isFunctionLike() const { return isFunctionLike_; }
41   std::size_t argumentCount() const { return argumentCount_; }
42   bool isVariadic() const { return isVariadic_; }
43   bool isDisabled() const { return isDisabled_; }
44   bool isPredefined() const { return isPredefined_; }
45   const TokenSequence &replacement() const { return replacement_; }
46 
47   bool set_isDisabled(bool disable);
48 
49   TokenSequence Apply(const std::vector<TokenSequence> &args, AllSources &);
50 
51 private:
52   static TokenSequence Tokenize(const std::vector<std::string> &argNames,
53       const TokenSequence &token, std::size_t firstToken, std::size_t tokens);
54 
55   bool isFunctionLike_{false};
56   std::size_t argumentCount_{0};
57   bool isVariadic_{false};
58   bool isDisabled_{false};
59   bool isPredefined_{false};
60   TokenSequence replacement_;
61 };
62 
63 // Preprocessing state
64 class Preprocessor {
65 public:
66   explicit Preprocessor(AllSources &);
67 
68   void Define(std::string macro, std::string value);
69   void Undefine(std::string macro);
70 
71   std::optional<TokenSequence> MacroReplacement(
72       const TokenSequence &, const Prescanner &);
73 
74   // Implements a preprocessor directive.
75   void Directive(const TokenSequence &, Prescanner *);
76 
77 private:
78   enum class IsElseActive { No, Yes };
79   enum class CanDeadElseAppear { No, Yes };
80 
81   CharBlock SaveTokenAsName(const CharBlock &);
82   bool IsNameDefined(const CharBlock &);
83   TokenSequence ReplaceMacros(const TokenSequence &, const Prescanner &);
84   void SkipDisabledConditionalCode(
85       const std::string &, IsElseActive, Prescanner *, ProvenanceRange);
86   bool IsIfPredicateTrue(const TokenSequence &expr, std::size_t first,
87       std::size_t exprTokens, Prescanner *);
88 
89   AllSources &allSources_;
90   std::list<std::string> names_;
91   std::unordered_map<CharBlock, Definition> definitions_;
92   std::stack<CanDeadElseAppear> ifStack_;
93 };
94 } // namespace Fortran::parser
95 #endif // FORTRAN_PARSER_PREPROCESSOR_H_
96