1 //===- ScriptParser.cpp ---------------------------------------------------===//
2 //
3 //                             The LLVM Linker
4 //
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
7 //
8 //===----------------------------------------------------------------------===//
9 //
10 // This file contains the base parser class for linker script and dynamic
11 // list.
12 //
13 //===----------------------------------------------------------------------===//
14 
15 #include "ScriptParser.h"
16 #include "Error.h"
17 #include "llvm/ADT/Twine.h"
18 
19 using namespace llvm;
20 using namespace lld;
21 using namespace lld::elf;
22 
23 // Returns a whole line containing the current token.
24 StringRef ScriptParserBase::getLine() {
25   StringRef S = getCurrentMB().getBuffer();
26   StringRef Tok = Tokens[Pos - 1];
27 
28   size_t Pos = S.rfind('\n', Tok.data() - S.data());
29   if (Pos != StringRef::npos)
30     S = S.substr(Pos + 1);
31   return S.substr(0, S.find_first_of("\r\n"));
32 }
33 
34 // Returns 1-based line number of the current token.
35 size_t ScriptParserBase::getLineNumber() {
36   StringRef S = getCurrentMB().getBuffer();
37   StringRef Tok = Tokens[Pos - 1];
38   return S.substr(0, Tok.data() - S.data()).count('\n') + 1;
39 }
40 
41 // Returns 0-based column number of the current token.
42 size_t ScriptParserBase::getColumnNumber() {
43   StringRef Tok = Tokens[Pos - 1];
44   return Tok.data() - getLine().data();
45 }
46 
47 std::string ScriptParserBase::getCurrentLocation() {
48   std::string Filename = getCurrentMB().getBufferIdentifier();
49   if (!Pos)
50     return Filename;
51   return (Filename + ":" + Twine(getLineNumber())).str();
52 }
53 
54 ScriptParserBase::ScriptParserBase(MemoryBufferRef MB) { tokenize(MB); }
55 
56 // We don't want to record cascading errors. Keep only the first one.
57 void ScriptParserBase::setError(const Twine &Msg) {
58   if (Error)
59     return;
60   Error = true;
61 
62   if (!Pos) {
63     error(getCurrentLocation() + ": " + Msg);
64     return;
65   }
66 
67   std::string S = getCurrentLocation() + ": ";
68   error(S + Msg);
69   error(S + getLine());
70   error(S + std::string(getColumnNumber(), ' ') + "^");
71 }
72 
73 // Split S into linker script tokens.
74 void ScriptParserBase::tokenize(MemoryBufferRef MB) {
75   std::vector<StringRef> Vec;
76   MBs.push_back(MB);
77   StringRef S = MB.getBuffer();
78   StringRef Begin = S;
79 
80   for (;;) {
81     S = skipSpace(S);
82     if (S.empty())
83       break;
84 
85     // Quoted token. Note that double-quote characters are parts of a token
86     // because, in a glob match context, only unquoted tokens are interpreted
87     // as glob patterns. Double-quoted tokens are literal patterns in that
88     // context.
89     if (S.startswith("\"")) {
90       size_t E = S.find("\"", 1);
91       if (E == StringRef::npos) {
92         StringRef Filename = MB.getBufferIdentifier();
93         size_t Lineno = Begin.substr(0, S.data() - Begin.data()).count('\n');
94         error(Filename + ":" + Twine(Lineno + 1) + ": unclosed quote");
95         return;
96       }
97 
98       Vec.push_back(S.take_front(E + 1));
99       S = S.substr(E + 1);
100       continue;
101     }
102 
103     // Unquoted token. This is more relaxed than tokens in C-like language,
104     // so that you can write "file-name.cpp" as one bare token, for example.
105     size_t Pos = S.find_first_not_of(
106         "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz"
107         "0123456789_.$/\\~=+[]*?-:!<>^");
108 
109     // A character that cannot start a word (which is usually a
110     // punctuation) forms a single character token.
111     if (Pos == 0)
112       Pos = 1;
113     Vec.push_back(S.substr(0, Pos));
114     S = S.substr(Pos);
115   }
116 
117   Tokens.insert(Tokens.begin() + Pos, Vec.begin(), Vec.end());
118 }
119 
120 // Skip leading whitespace characters or comments.
121 StringRef ScriptParserBase::skipSpace(StringRef S) {
122   for (;;) {
123     if (S.startswith("/*")) {
124       size_t E = S.find("*/", 2);
125       if (E == StringRef::npos) {
126         error("unclosed comment in a linker script");
127         return "";
128       }
129       S = S.substr(E + 2);
130       continue;
131     }
132     if (S.startswith("#")) {
133       size_t E = S.find('\n', 1);
134       if (E == StringRef::npos)
135         E = S.size() - 1;
136       S = S.substr(E + 1);
137       continue;
138     }
139     size_t Size = S.size();
140     S = S.ltrim();
141     if (S.size() == Size)
142       return S;
143   }
144 }
145 
146 // An erroneous token is handled as if it were the last token before EOF.
147 bool ScriptParserBase::atEOF() { return Error || Tokens.size() == Pos; }
148 
149 StringRef ScriptParserBase::next() {
150   if (Error)
151     return "";
152   if (atEOF()) {
153     setError("unexpected EOF");
154     return "";
155   }
156   return Tokens[Pos++];
157 }
158 
159 StringRef ScriptParserBase::peek() {
160   StringRef Tok = next();
161   if (Error)
162     return "";
163   --Pos;
164   return Tok;
165 }
166 
167 bool ScriptParserBase::consume(StringRef Tok) {
168   if (peek() == Tok) {
169     skip();
170     return true;
171   }
172   return false;
173 }
174 
175 void ScriptParserBase::skip() { (void)next(); }
176 
177 void ScriptParserBase::expect(StringRef Expect) {
178   if (Error)
179     return;
180   StringRef Tok = next();
181   if (Tok != Expect)
182     setError(Expect + " expected, but got " + Tok);
183 }
184 
185 // Returns true if S encloses T.
186 static bool encloses(StringRef S, StringRef T) {
187   return S.bytes_begin() <= T.bytes_begin() && T.bytes_end() <= S.bytes_end();
188 }
189 
190 MemoryBufferRef ScriptParserBase::getCurrentMB() {
191   // Find input buffer containing the current token.
192   assert(!MBs.empty());
193   if (!Pos)
194     return MBs[0];
195 
196   for (MemoryBufferRef MB : MBs)
197     if (encloses(MB.getBuffer(), Tokens[Pos - 1]))
198       return MB;
199   llvm_unreachable("getCurrentMB: failed to find a token");
200 }
201