1//===--- RewriteMacros.cpp - Rewrite macros into their expansions ---------===//
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// This code rewrites macro invocations into their expansions. This gives you
10// a macro expanded file that retains comments and #includes.
11//
12//===----------------------------------------------------------------------===//
13
14#include "clang/Rewrite/Frontend/Rewriters.h"
15#include "clang/Basic/SourceManager.h"
16#include "clang/Lex/Preprocessor.h"
17#include "clang/Rewrite/Core/Rewriter.h"
18#include "llvm/Support/Path.h"
19#include "llvm/Support/raw_ostream.h"
20#include <cstdio>
21#include <memory>
22
23using namespace clang;
24
25/// isSameToken - Return true if the two specified tokens start have the same
26/// content.
27static bool isSameToken(Token &RawTok, Token &PPTok) {
28 // If two tokens have the same kind and the same identifier info, they are
29 // obviously the same.
30 if (PPTok.getKind() == RawTok.getKind() &&
31 PPTok.getIdentifierInfo() == RawTok.getIdentifierInfo())
32 return true;
33
34 // Otherwise, if they are different but have the same identifier info, they
35 // are also considered to be the same. This allows keywords and raw lexed
36 // identifiers with the same name to be treated the same.
37 if (PPTok.getIdentifierInfo() &&
38 PPTok.getIdentifierInfo() == RawTok.getIdentifierInfo())
39 return true;
40
41 return false;
42}
43
44
45/// GetNextRawTok - Return the next raw token in the stream, skipping over
46/// comments if ReturnComment is false.
47static const Token &GetNextRawTok(const std::vector<Token> &RawTokens,
48 unsigned &CurTok, bool ReturnComment) {
49 assert(CurTok < RawTokens.size() && "Overran eof!");
50
51 // If the client doesn't want comments and we have one, skip it.
52 if (!ReturnComment && RawTokens[CurTok].is(K: tok::comment))
53 ++CurTok;
54
55 return RawTokens[CurTok++];
56}
57
58
59/// LexRawTokensFromMainFile - Lets all the raw tokens from the main file into
60/// the specified vector.
61static void LexRawTokensFromMainFile(Preprocessor &PP,
62 std::vector<Token> &RawTokens) {
63 SourceManager &SM = PP.getSourceManager();
64
65 // Create a lexer to lex all the tokens of the main file in raw mode. Even
66 // though it is in raw mode, it will not return comments.
67 llvm::MemoryBufferRef FromFile = SM.getBufferOrFake(FID: SM.getMainFileID());
68 Lexer RawLex(SM.getMainFileID(), FromFile, SM, PP.getLangOpts());
69
70 // Switch on comment lexing because we really do want them.
71 RawLex.SetCommentRetentionState(true);
72
73 Token RawTok;
74 do {
75 RawLex.LexFromRawLexer(Result&: RawTok);
76
77 // If we have an identifier with no identifier info for our raw token, look
78 // up the identifier info. This is important for equality comparison of
79 // identifier tokens.
80 if (RawTok.is(K: tok::raw_identifier))
81 PP.LookUpIdentifierInfo(Identifier&: RawTok);
82
83 RawTokens.push_back(x: RawTok);
84 } while (RawTok.isNot(K: tok::eof));
85}
86
87
88/// RewriteMacrosInInput - Implement -rewrite-macros mode.
89void clang::RewriteMacrosInInput(Preprocessor &PP, raw_ostream *OS) {
90 SourceManager &SM = PP.getSourceManager();
91
92 Rewriter Rewrite;
93 Rewrite.setSourceMgr(SM, LO: PP.getLangOpts());
94 RewriteBuffer &RB = Rewrite.getEditBuffer(FID: SM.getMainFileID());
95
96 std::vector<Token> RawTokens;
97 LexRawTokensFromMainFile(PP, RawTokens);
98 unsigned CurRawTok = 0;
99 Token RawTok = GetNextRawTok(RawTokens, CurTok&: CurRawTok, ReturnComment: false);
100
101
102 // Get the first preprocessing token.
103 PP.EnterMainSourceFile();
104 Token PPTok;
105 PP.Lex(Result&: PPTok);
106
107 // Preprocess the input file in parallel with raw lexing the main file. Ignore
108 // all tokens that are preprocessed from a file other than the main file (e.g.
109 // a header). If we see tokens that are in the preprocessed file but not the
110 // lexed file, we have a macro expansion. If we see tokens in the lexed file
111 // that aren't in the preprocessed view, we have macros that expand to no
112 // tokens, or macro arguments etc.
113 while (RawTok.isNot(K: tok::eof) || PPTok.isNot(K: tok::eof)) {
114 SourceLocation PPLoc = SM.getExpansionLoc(Loc: PPTok.getLocation());
115
116 // If PPTok is from a different source file, ignore it.
117 if (!SM.isWrittenInMainFile(Loc: PPLoc)) {
118 PP.Lex(Result&: PPTok);
119 continue;
120 }
121
122 // If the raw file hits a preprocessor directive, they will be extra tokens
123 // in the raw file that don't exist in the preprocsesed file. However, we
124 // choose to preserve them in the output file and otherwise handle them
125 // specially.
126 if (RawTok.is(K: tok::hash) && RawTok.isAtStartOfLine()) {
127 // If this is a #warning directive or #pragma mark (GNU extensions),
128 // comment the line out.
129 if (RawTokens[CurRawTok].is(K: tok::identifier)) {
130 const IdentifierInfo *II = RawTokens[CurRawTok].getIdentifierInfo();
131 if (II->getName() == "warning") {
132 // Comment out #warning.
133 RB.InsertTextAfter(OrigOffset: SM.getFileOffset(SpellingLoc: RawTok.getLocation()), Str: "//");
134 } else if (II->getName() == "pragma" &&
135 RawTokens[CurRawTok+1].is(K: tok::identifier) &&
136 (RawTokens[CurRawTok+1].getIdentifierInfo()->getName() ==
137 "mark")) {
138 // Comment out #pragma mark.
139 RB.InsertTextAfter(OrigOffset: SM.getFileOffset(SpellingLoc: RawTok.getLocation()), Str: "//");
140 }
141 }
142
143 // Otherwise, if this is a #include or some other directive, just leave it
144 // in the file by skipping over the line.
145 RawTok = GetNextRawTok(RawTokens, CurTok&: CurRawTok, ReturnComment: false);
146 while (!RawTok.isAtStartOfLine() && RawTok.isNot(K: tok::eof))
147 RawTok = GetNextRawTok(RawTokens, CurTok&: CurRawTok, ReturnComment: false);
148 continue;
149 }
150
151 // Okay, both tokens are from the same file. Get their offsets from the
152 // start of the file.
153 unsigned PPOffs = SM.getFileOffset(SpellingLoc: PPLoc);
154 unsigned RawOffs = SM.getFileOffset(SpellingLoc: RawTok.getLocation());
155
156 // If the offsets are the same and the token kind is the same, ignore them.
157 if (PPOffs == RawOffs && isSameToken(RawTok, PPTok)) {
158 RawTok = GetNextRawTok(RawTokens, CurTok&: CurRawTok, ReturnComment: false);
159 PP.Lex(Result&: PPTok);
160 continue;
161 }
162
163 // If the PP token is farther along than the raw token, something was
164 // deleted. Comment out the raw token.
165 if (RawOffs <= PPOffs) {
166 // Comment out a whole run of tokens instead of bracketing each one with
167 // comments. Add a leading space if RawTok didn't have one.
168 bool HasSpace = RawTok.hasLeadingSpace();
169 RB.InsertTextAfter(OrigOffset: RawOffs, Str: &" /*"[HasSpace]);
170 unsigned EndPos;
171
172 do {
173 EndPos = RawOffs+RawTok.getLength();
174
175 RawTok = GetNextRawTok(RawTokens, CurTok&: CurRawTok, ReturnComment: true);
176 RawOffs = SM.getFileOffset(SpellingLoc: RawTok.getLocation());
177
178 if (RawTok.is(K: tok::comment)) {
179 // Skip past the comment.
180 RawTok = GetNextRawTok(RawTokens, CurTok&: CurRawTok, ReturnComment: false);
181 break;
182 }
183
184 } while (RawOffs <= PPOffs && !RawTok.isAtStartOfLine() &&
185 (PPOffs != RawOffs || !isSameToken(RawTok, PPTok)));
186
187 RB.InsertTextBefore(OrigOffset: EndPos, Str: "*/");
188 continue;
189 }
190
191 // Otherwise, there was a replacement an expansion. Insert the new token
192 // in the output buffer. Insert the whole run of new tokens at once to get
193 // them in the right order.
194 unsigned InsertPos = PPOffs;
195 std::string Expansion;
196 while (PPOffs < RawOffs) {
197 Expansion += ' ' + PP.getSpelling(Tok: PPTok);
198 PP.Lex(Result&: PPTok);
199 PPLoc = SM.getExpansionLoc(Loc: PPTok.getLocation());
200 PPOffs = SM.getFileOffset(SpellingLoc: PPLoc);
201 }
202 Expansion += ' ';
203 RB.InsertTextBefore(OrigOffset: InsertPos, Str: Expansion);
204 }
205
206 // Get the buffer corresponding to MainFileID. If we haven't changed it, then
207 // we are done.
208 if (const RewriteBuffer *RewriteBuf =
209 Rewrite.getRewriteBufferFor(FID: SM.getMainFileID())) {
210 //printf("Changed:\n");
211 *OS << std::string(RewriteBuf->begin(), RewriteBuf->end());
212 } else {
213 fprintf(stderr, format: "No changes\n");
214 }
215 OS->flush();
216}
217