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 the line that the character S[Pos] is in.
24 static StringRef getLine(StringRef S, size_t Pos) {
25   size_t Begin = S.rfind('\n', Pos);
26   size_t End = S.find('\n', Pos);
27   Begin = (Begin == StringRef::npos) ? 0 : Begin + 1;
28   if (End == StringRef::npos)
29     End = S.size();
30   // rtrim for DOS-style newlines.
31   return S.substr(Begin, End - Begin).rtrim();
32 }
33 
34 void ScriptParserBase::printErrorPos() {
35   StringRef Tok = Tokens[Pos == 0 ? 0 : Pos - 1];
36   StringRef Line = getLine(Input, Tok.data() - Input.data());
37   size_t Col = Tok.data() - Line.data();
38   error(Line);
39   error(std::string(Col, ' ') + "^");
40 }
41 
42 // We don't want to record cascading errors. Keep only the first one.
43 void ScriptParserBase::setError(const Twine &Msg) {
44   if (Error)
45     return;
46   if (Input.empty() || Tokens.empty()) {
47     error(Msg);
48   } else {
49     error("line " + Twine(getPos()) + ": " + Msg);
50     printErrorPos();
51   }
52   Error = true;
53 }
54 
55 // Split S into linker script tokens.
56 std::vector<StringRef> ScriptParserBase::tokenize(StringRef S) {
57   std::vector<StringRef> Ret;
58   for (;;) {
59     S = skipSpace(S);
60     if (S.empty())
61       return Ret;
62 
63     // Quoted token
64     if (S.startswith("\"")) {
65       size_t E = S.find("\"", 1);
66       if (E == StringRef::npos) {
67         error("unclosed quote");
68         return {};
69       }
70       Ret.push_back(S.substr(1, E - 1));
71       S = S.substr(E + 1);
72       continue;
73     }
74 
75     // Unquoted token
76     size_t Pos = S.find_first_not_of(
77         "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz"
78         "0123456789_.$/\\~=+[]*?-:!<>");
79     // A character that cannot start a word (which is usually a
80     // punctuation) forms a single character token.
81     if (Pos == 0)
82       Pos = 1;
83     Ret.push_back(S.substr(0, Pos));
84     S = S.substr(Pos);
85   }
86 }
87 
88 // Skip leading whitespace characters or comments.
89 StringRef ScriptParserBase::skipSpace(StringRef S) {
90   for (;;) {
91     if (S.startswith("/*")) {
92       size_t E = S.find("*/", 2);
93       if (E == StringRef::npos) {
94         error("unclosed comment in a linker script");
95         return "";
96       }
97       S = S.substr(E + 2);
98       continue;
99     }
100     if (S.startswith("#")) {
101       size_t E = S.find('\n', 1);
102       if (E == StringRef::npos)
103         E = S.size() - 1;
104       S = S.substr(E + 1);
105       continue;
106     }
107     size_t Size = S.size();
108     S = S.ltrim();
109     if (S.size() == Size)
110       return S;
111   }
112 }
113 
114 // An erroneous token is handled as if it were the last token before EOF.
115 bool ScriptParserBase::atEOF() { return Error || Tokens.size() == Pos; }
116 
117 StringRef ScriptParserBase::next() {
118   if (Error)
119     return "";
120   if (atEOF()) {
121     setError("unexpected EOF");
122     return "";
123   }
124   return Tokens[Pos++];
125 }
126 
127 StringRef ScriptParserBase::peek() {
128   StringRef Tok = next();
129   if (Error)
130     return "";
131   --Pos;
132   return Tok;
133 }
134 
135 bool ScriptParserBase::skip(StringRef Tok) {
136   if (Error)
137     return false;
138   if (atEOF()) {
139     setError("unexpected EOF");
140     return false;
141   }
142   if (Tokens[Pos] != Tok)
143     return false;
144   ++Pos;
145   return true;
146 }
147 
148 void ScriptParserBase::expect(StringRef Expect) {
149   if (Error)
150     return;
151   StringRef Tok = next();
152   if (Tok != Expect)
153     setError(Expect + " expected, but got " + Tok);
154 }
155 
156 // Returns the current line number.
157 size_t ScriptParserBase::getPos() {
158   if (Pos == 0)
159     return 1;
160   const char *Begin = Input.data();
161   const char *Tok = Tokens[Pos - 1].data();
162   return StringRef(Begin, Tok - Begin).count('\n') + 1;
163 }
164