forked from OSchip/llvm-project
304 lines
9.0 KiB
C++
304 lines
9.0 KiB
C++
//===- ScriptLexer.cpp ----------------------------------------------------===//
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//
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// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
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// See https://llvm.org/LICENSE.txt for license information.
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// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
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//
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//===----------------------------------------------------------------------===//
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//
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// This file defines a lexer for the linker script.
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//
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// The linker script's grammar is not complex but ambiguous due to the
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// lack of the formal specification of the language. What we are trying to
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// do in this and other files in LLD is to make a "reasonable" linker
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// script processor.
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//
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// Among simplicity, compatibility and efficiency, we put the most
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// emphasis on simplicity when we wrote this lexer. Compatibility with the
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// GNU linkers is important, but we did not try to clone every tiny corner
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// case of their lexers, as even ld.bfd and ld.gold are subtly different
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// in various corner cases. We do not care much about efficiency because
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// the time spent in parsing linker scripts is usually negligible.
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//
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// Our grammar of the linker script is LL(2), meaning that it needs at
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// most two-token lookahead to parse. The only place we need two-token
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// lookahead is labels in version scripts, where we need to parse "local :"
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// as if "local:".
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//
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// Overall, this lexer works fine for most linker scripts. There might
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// be room for improving compatibility, but that's probably not at the
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// top of our todo list.
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//
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//===----------------------------------------------------------------------===//
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#include "ScriptLexer.h"
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#include "lld/Common/ErrorHandler.h"
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#include "llvm/ADT/Twine.h"
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using namespace llvm;
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namespace lld {
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namespace elf {
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// Returns a whole line containing the current token.
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StringRef ScriptLexer::getLine() {
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StringRef s = getCurrentMB().getBuffer();
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StringRef tok = tokens[pos - 1];
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size_t pos = s.rfind('\n', tok.data() - s.data());
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if (pos != StringRef::npos)
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s = s.substr(pos + 1);
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return s.substr(0, s.find_first_of("\r\n"));
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}
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// Returns 1-based line number of the current token.
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size_t ScriptLexer::getLineNumber() {
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StringRef s = getCurrentMB().getBuffer();
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StringRef tok = tokens[pos - 1];
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return s.substr(0, tok.data() - s.data()).count('\n') + 1;
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}
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// Returns 0-based column number of the current token.
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size_t ScriptLexer::getColumnNumber() {
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StringRef tok = tokens[pos - 1];
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return tok.data() - getLine().data();
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}
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std::string ScriptLexer::getCurrentLocation() {
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std::string filename = std::string(getCurrentMB().getBufferIdentifier());
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return (filename + ":" + Twine(getLineNumber())).str();
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}
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ScriptLexer::ScriptLexer(MemoryBufferRef mb) { tokenize(mb); }
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// We don't want to record cascading errors. Keep only the first one.
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void ScriptLexer::setError(const Twine &msg) {
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if (errorCount())
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return;
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std::string s = (getCurrentLocation() + ": " + msg).str();
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if (pos)
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s += "\n>>> " + getLine().str() + "\n>>> " +
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std::string(getColumnNumber(), ' ') + "^";
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error(s);
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}
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// Split S into linker script tokens.
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void ScriptLexer::tokenize(MemoryBufferRef mb) {
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std::vector<StringRef> vec;
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mbs.push_back(mb);
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StringRef s = mb.getBuffer();
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StringRef begin = s;
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for (;;) {
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s = skipSpace(s);
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if (s.empty())
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break;
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// Quoted token. Note that double-quote characters are parts of a token
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// because, in a glob match context, only unquoted tokens are interpreted
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// as glob patterns. Double-quoted tokens are literal patterns in that
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// context.
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if (s.startswith("\"")) {
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size_t e = s.find("\"", 1);
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if (e == StringRef::npos) {
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StringRef filename = mb.getBufferIdentifier();
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size_t lineno = begin.substr(0, s.data() - begin.data()).count('\n');
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error(filename + ":" + Twine(lineno + 1) + ": unclosed quote");
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return;
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}
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vec.push_back(s.take_front(e + 1));
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s = s.substr(e + 1);
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continue;
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}
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// ">foo" is parsed to ">" and "foo", but ">>" is parsed to ">>".
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// "|", "||", "&" and "&&" are different operators.
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if (s.startswith("<<") || s.startswith("<=") || s.startswith(">>") ||
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s.startswith(">=") || s.startswith("||") || s.startswith("&&")) {
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vec.push_back(s.substr(0, 2));
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s = s.substr(2);
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continue;
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}
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// Unquoted token. This is more relaxed than tokens in C-like language,
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// so that you can write "file-name.cpp" as one bare token, for example.
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size_t pos = s.find_first_not_of(
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"ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz"
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"0123456789_.$/\\~=+[]*?-!^:");
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// A character that cannot start a word (which is usually a
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// punctuation) forms a single character token.
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if (pos == 0)
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pos = 1;
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vec.push_back(s.substr(0, pos));
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s = s.substr(pos);
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}
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tokens.insert(tokens.begin() + pos, vec.begin(), vec.end());
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}
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// Skip leading whitespace characters or comments.
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StringRef ScriptLexer::skipSpace(StringRef s) {
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for (;;) {
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if (s.startswith("/*")) {
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size_t e = s.find("*/", 2);
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if (e == StringRef::npos) {
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error("unclosed comment in a linker script");
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return "";
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}
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s = s.substr(e + 2);
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continue;
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}
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if (s.startswith("#")) {
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size_t e = s.find('\n', 1);
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if (e == StringRef::npos)
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e = s.size() - 1;
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s = s.substr(e + 1);
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continue;
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}
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size_t size = s.size();
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s = s.ltrim();
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if (s.size() == size)
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return s;
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}
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}
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// An erroneous token is handled as if it were the last token before EOF.
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bool ScriptLexer::atEOF() { return errorCount() || tokens.size() == pos; }
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// Split a given string as an expression.
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// This function returns "3", "*" and "5" for "3*5" for example.
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static std::vector<StringRef> tokenizeExpr(StringRef s) {
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StringRef ops = "+-*/:!~=<>"; // List of operators
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// Quoted strings are literal strings, so we don't want to split it.
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if (s.startswith("\""))
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return {s};
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// Split S with operators as separators.
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std::vector<StringRef> ret;
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while (!s.empty()) {
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size_t e = s.find_first_of(ops);
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// No need to split if there is no operator.
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if (e == StringRef::npos) {
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ret.push_back(s);
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break;
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}
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// Get a token before the operator.
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if (e != 0)
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ret.push_back(s.substr(0, e));
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// Get the operator as a token.
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// Keep !=, ==, >=, <=, << and >> operators as a single tokens.
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if (s.substr(e).startswith("!=") || s.substr(e).startswith("==") ||
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s.substr(e).startswith(">=") || s.substr(e).startswith("<=") ||
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s.substr(e).startswith("<<") || s.substr(e).startswith(">>")) {
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ret.push_back(s.substr(e, 2));
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s = s.substr(e + 2);
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} else {
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ret.push_back(s.substr(e, 1));
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s = s.substr(e + 1);
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}
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}
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return ret;
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}
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// In contexts where expressions are expected, the lexer should apply
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// different tokenization rules than the default one. By default,
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// arithmetic operator characters are regular characters, but in the
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// expression context, they should be independent tokens.
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//
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// For example, "foo*3" should be tokenized to "foo", "*" and "3" only
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// in the expression context.
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//
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// This function may split the current token into multiple tokens.
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void ScriptLexer::maybeSplitExpr() {
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if (!inExpr || errorCount() || atEOF())
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return;
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std::vector<StringRef> v = tokenizeExpr(tokens[pos]);
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if (v.size() == 1)
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return;
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tokens.erase(tokens.begin() + pos);
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tokens.insert(tokens.begin() + pos, v.begin(), v.end());
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}
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StringRef ScriptLexer::next() {
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maybeSplitExpr();
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if (errorCount())
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return "";
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if (atEOF()) {
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setError("unexpected EOF");
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return "";
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}
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return tokens[pos++];
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}
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StringRef ScriptLexer::peek() {
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StringRef tok = next();
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if (errorCount())
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return "";
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pos = pos - 1;
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return tok;
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}
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StringRef ScriptLexer::peek2() {
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skip();
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StringRef tok = next();
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if (errorCount())
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return "";
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pos = pos - 2;
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return tok;
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}
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bool ScriptLexer::consume(StringRef tok) {
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if (peek() == tok) {
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skip();
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return true;
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}
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return false;
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}
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// Consumes Tok followed by ":". Space is allowed between Tok and ":".
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bool ScriptLexer::consumeLabel(StringRef tok) {
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if (consume((tok + ":").str()))
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return true;
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if (tokens.size() >= pos + 2 && tokens[pos] == tok &&
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tokens[pos + 1] == ":") {
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pos += 2;
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return true;
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}
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return false;
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}
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void ScriptLexer::skip() { (void)next(); }
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void ScriptLexer::expect(StringRef expect) {
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if (errorCount())
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return;
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StringRef tok = next();
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if (tok != expect)
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setError(expect + " expected, but got " + tok);
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}
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// Returns true if S encloses T.
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static bool encloses(StringRef s, StringRef t) {
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return s.bytes_begin() <= t.bytes_begin() && t.bytes_end() <= s.bytes_end();
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}
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MemoryBufferRef ScriptLexer::getCurrentMB() {
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// Find input buffer containing the current token.
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assert(!mbs.empty() && pos > 0);
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for (MemoryBufferRef mb : mbs)
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if (encloses(mb.getBuffer(), tokens[pos - 1]))
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return mb;
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llvm_unreachable("getCurrentMB: failed to find a token");
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}
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} // namespace elf
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} // namespace lld
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