[ELF] Better error reporting for linker scripts

Differential revision: https://reviews.llvm.org/D26795

llvm-svn: 287547
diff --git a/lld/ELF/DriverUtils.cpp b/lld/ELF/DriverUtils.cpp
index 546256b..d56dfba 100644
--- a/lld/ELF/DriverUtils.cpp
+++ b/lld/ELF/DriverUtils.cpp
@@ -99,7 +99,7 @@
 void elf::parseDynamicList(MemoryBufferRef MB) {
   class Parser : public ScriptParserBase {
   public:
-    Parser(StringRef S) : ScriptParserBase(S) {}
+    Parser(MemoryBufferRef MB) : ScriptParserBase(MB) {}
 
     void run() {
       while (!atEOF()) {
@@ -113,7 +113,7 @@
     }
   };
 
-  Parser(MB.getBuffer()).run();
+  Parser(MB).run();
 }
 
 void elf::printHelp(const char *Argv0) {
diff --git a/lld/ELF/LinkerScript.cpp b/lld/ELF/LinkerScript.cpp
index ff58e44..38477c8 100644
--- a/lld/ELF/LinkerScript.cpp
+++ b/lld/ELF/LinkerScript.cpp
@@ -33,7 +33,6 @@
 #include "llvm/Support/ErrorHandling.h"
 #include "llvm/Support/FileSystem.h"
 #include "llvm/Support/MathExtras.h"
-#include "llvm/Support/MemoryBuffer.h"
 #include "llvm/Support/Path.h"
 #include <algorithm>
 #include <cassert>
@@ -948,11 +947,12 @@
   return 0;
 }
 
-class elf::ScriptParser : public ScriptParserBase {
+class elf::ScriptParser final : public ScriptParserBase {
   typedef void (ScriptParser::*Handler)();
 
 public:
-  ScriptParser(StringRef S, bool B) : ScriptParserBase(S), IsUnderSysroot(B) {}
+  ScriptParser(MemoryBufferRef MB, bool B)
+      : ScriptParserBase(MB), IsUnderSysroot(B) {}
 
   void readLinkerScript();
   void readVersionScript();
@@ -1006,6 +1006,7 @@
 
   ScriptConfiguration &Opt = *ScriptConfig;
   bool IsUnderSysroot;
+  std::vector<std::unique_ptr<MemoryBuffer>> OwningMBs;
 };
 
 void ScriptParser::readVersionScript() {
@@ -1148,9 +1149,8 @@
     return;
   }
   std::unique_ptr<MemoryBuffer> &MB = *MBOrErr;
-  StringRef S = Saver.save(MB->getMemBufferRef().getBuffer());
-  std::vector<StringRef> V = tokenize(S);
-  Tokens.insert(Tokens.begin() + Pos, V.begin(), V.end());
+  tokenize(MB->getMemBufferRef());
+  OwningMBs.push_back(std::move(MB));
 }
 
 void ScriptParser::readOutput() {
@@ -1912,11 +1912,11 @@
 
 void elf::readLinkerScript(MemoryBufferRef MB) {
   StringRef Path = MB.getBufferIdentifier();
-  ScriptParser(MB.getBuffer(), isUnderSysroot(Path)).readLinkerScript();
+  ScriptParser(MB, isUnderSysroot(Path)).readLinkerScript();
 }
 
 void elf::readVersionScript(MemoryBufferRef MB) {
-  ScriptParser(MB.getBuffer(), false).readVersionScript();
+  ScriptParser(MB, false).readVersionScript();
 }
 
 template class elf::LinkerScript<ELF32LE>;
diff --git a/lld/ELF/ScriptParser.cpp b/lld/ELF/ScriptParser.cpp
index 3c66af5..33c2f90 100644
--- a/lld/ELF/ScriptParser.cpp
+++ b/lld/ELF/ScriptParser.cpp
@@ -20,45 +20,59 @@
 using namespace lld;
 using namespace lld::elf;
 
-// Returns the line that the character S[Pos] is in.
-static StringRef getLine(StringRef S, size_t Pos) {
-  size_t Begin = S.rfind('\n', Pos);
-  size_t End = S.find('\n', Pos);
+// Returns the line that the token Tok is in.
+static StringRef getLine(StringRef Data, StringRef Tok) {
+  size_t Pos = Tok.data() - Data.data();
+  size_t Begin = Data.rfind('\n', Pos);
+  size_t End = Data.find('\n', Pos);
   Begin = (Begin == StringRef::npos) ? 0 : Begin + 1;
   if (End == StringRef::npos)
-    End = S.size();
+    End = Data.size();
   // rtrim for DOS-style newlines.
-  return S.substr(Begin, End - Begin).rtrim();
+  return Data.substr(Begin, End - Begin).rtrim();
 }
 
-void ScriptParserBase::printErrorPos() {
-  StringRef Tok = Tokens[Pos == 0 ? 0 : Pos - 1];
-  StringRef Line = getLine(Input, Tok.data() - Input.data());
-  size_t Col = Tok.data() - Line.data();
-  error(Line);
-  error(std::string(Col, ' ') + "^");
+static std::pair<size_t, size_t> getPos(StringRef Data, StringRef Tok) {
+  StringRef Line = getLine(Data, Tok);
+  size_t LineNo =
+      StringRef(Data.data(), Tok.data() - Data.data()).count('\n') + 1;
+  return {LineNo, Tok.data() - Line.data()};
 }
 
+ScriptParserBase::ScriptParserBase(MemoryBufferRef MB) { tokenize(MB); }
+
 // We don't want to record cascading errors. Keep only the first one.
 void ScriptParserBase::setError(const Twine &Msg) {
   if (Error)
     return;
-  if (Input.empty() || Tokens.empty()) {
-    error(Msg);
-  } else {
-    error("line " + Twine(getPos()) + ": " + Msg);
-    printErrorPos();
+
+  std::pair<size_t, size_t> ErrPos;
+  MemoryBufferRef MB = currentBuffer();
+  std::string Location = MB.getBufferIdentifier();
+  if (Pos) {
+    ErrPos = getPos(MB.getBuffer(), Tokens[Pos - 1]);
+    Location += ":";
+    Location += std::to_string(ErrPos.first);
   }
+  error(Location + ": " + Msg);
+  if (Pos) {
+    error(Location + ": " + getLine(MB.getBuffer(), Tokens[Pos - 1]));
+    error(Location + ": " + std::string(ErrPos.second, ' ') + "^");
+  }
+
   Error = true;
 }
 
 // Split S into linker script tokens.
-std::vector<StringRef> ScriptParserBase::tokenize(StringRef S) {
+void ScriptParserBase::tokenize(MemoryBufferRef MB) {
   std::vector<StringRef> Ret;
+  MBs.push_back(MB);
+  StringRef S = MB.getBuffer();
+  StringRef Begin = S;
   for (;;) {
     S = skipSpace(S);
     if (S.empty())
-      return Ret;
+      break;
 
     // Quoted token. Note that double-quote characters are parts of a token
     // because, in a glob match context, only unquoted tokens are interpreted
@@ -67,8 +81,10 @@
     if (S.startswith("\"")) {
       size_t E = S.find("\"", 1);
       if (E == StringRef::npos) {
-        error("unclosed quote");
-        return {};
+        auto ErrPos = getPos(Begin, S);
+        error(MB.getBufferIdentifier() + ":" + Twine(ErrPos.first) +
+              ": unclosed quote");
+        return;
       }
       Ret.push_back(S.take_front(E + 1));
       S = S.substr(E + 1);
@@ -88,6 +104,7 @@
     Ret.push_back(S.substr(0, Pos));
     S = S.substr(Pos);
   }
+  Tokens.insert(Tokens.begin() + Pos, Ret.begin(), Ret.end());
 }
 
 // Skip leading whitespace characters or comments.
@@ -155,11 +172,21 @@
     setError(Expect + " expected, but got " + Tok);
 }
 
-// Returns the current line number.
-size_t ScriptParserBase::getPos() {
-  if (Pos == 0)
-    return 1;
-  const char *Begin = Input.data();
-  const char *Tok = Tokens[Pos - 1].data();
-  return StringRef(Begin, Tok - Begin).count('\n') + 1;
+// Returns true if string 'Bigger' contains string 'Shorter'.
+static bool containsString(StringRef Bigger, StringRef Shorter) {
+  const char *BiggerEnd = Bigger.data() + Bigger.size();
+  const char *ShorterEnd = Shorter.data() + Shorter.size();
+
+  return Bigger.data() <= Shorter.data() && BiggerEnd >= ShorterEnd;
+}
+
+MemoryBufferRef ScriptParserBase::currentBuffer() {
+  // Find input buffer containing the current token.
+  assert(!MBs.empty());
+  if (Pos)
+    for (MemoryBufferRef MB : MBs)
+      if (containsString(MB.getBuffer(), Tokens[Pos - 1]))
+        return MB;
+
+  return MBs.front();
 }
diff --git a/lld/ELF/ScriptParser.h b/lld/ELF/ScriptParser.h
index e2bdeef..6c314a4 100644
--- a/lld/ELF/ScriptParser.h
+++ b/lld/ELF/ScriptParser.h
@@ -12,6 +12,7 @@
 
 #include "lld/Core/LLVM.h"
 #include "llvm/ADT/StringRef.h"
+#include "llvm/Support/MemoryBuffer.h"
 #include <utility>
 #include <vector>
 
@@ -20,11 +21,10 @@
 
 class ScriptParserBase {
 public:
-  explicit ScriptParserBase(StringRef S) : Input(S), Tokens(tokenize(S)) {}
+  explicit ScriptParserBase(MemoryBufferRef MB);
 
-protected:
   void setError(const Twine &Msg);
-  static std::vector<StringRef> tokenize(StringRef S);
+  void tokenize(MemoryBufferRef MB);
   static StringRef skipSpace(StringRef S);
   bool atEOF();
   StringRef next();
@@ -33,13 +33,13 @@
   bool consume(StringRef Tok);
   void expect(StringRef Expect);
 
-  size_t getPos();
-  void printErrorPos();
-
-  StringRef Input;
+  std::vector<MemoryBufferRef> MBs;
   std::vector<StringRef> Tokens;
   size_t Pos = 0;
   bool Error = false;
+
+private:
+  MemoryBufferRef currentBuffer();
 };
 
 } // namespace elf