From 4a5a6337f7b79c8800dc0f5d7119f17b07e527ae Mon Sep 17 00:00:00 2001
From: Jonas Devlieghere <jonas@devlieghere.com>
Date: Tue, 26 Sep 2017 08:17:28 +0000
Subject: [PATCH] [dsymutil] Better support for symbol aliases

This patch adds logic to follow a symbol's aliases when the symbol name
cannot be found in the current object file. It checks the main binary
for the symbol's address and queries the current object for its aliases
(symbols with the same address) before printing out a warning.

Differential revision: https://reviews.llvm.org/D38230

llvm-svn: 314198
---
 llvm/test/tools/dsymutil/Inputs/alias/bar.o  | Bin 0 -> 1956 bytes
 llvm/test/tools/dsymutil/Inputs/alias/foo.o  | Bin 0 -> 1656 bytes
 llvm/test/tools/dsymutil/Inputs/alias/foobar | Bin 0 -> 8688 bytes
 llvm/test/tools/dsymutil/X86/alias.test      |  19 +++++++++++++++++++
 llvm/tools/dsymutil/MachODebugMapParser.cpp  |  24 ++++++++++++++++++++++++
 5 files changed, 43 insertions(+)
 create mode 100644 llvm/test/tools/dsymutil/Inputs/alias/bar.o
 create mode 100644 llvm/test/tools/dsymutil/Inputs/alias/foo.o
 create mode 100755 llvm/test/tools/dsymutil/Inputs/alias/foobar
 create mode 100644 llvm/test/tools/dsymutil/X86/alias.test

diff --git a/llvm/test/tools/dsymutil/Inputs/alias/bar.o b/llvm/test/tools/dsymutil/Inputs/alias/bar.o
new file mode 100644
index 0000000000000000000000000000000000000000..d98632f64308072ed66deb4f8f57b32e1aeaa230
GIT binary patch
literal 1956
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E4{zqkGXMYp

literal 0
HcmV?d00001

diff --git a/llvm/test/tools/dsymutil/Inputs/alias/foo.o b/llvm/test/tools/dsymutil/Inputs/alias/foo.o
new file mode 100644
index 0000000000000000000000000000000000000000..aff057285888d43eef4305a54a586279737ffb18
GIT binary patch
literal 1656
zcmb7^-D(p-6vt<?CPuf7l?qxES)|&QN)nsWi1mYj9~E!J23qi9-K3ik-Rv&A(_rs%
zS@F&%5cDB@0(<F$h%caE{hytgWV204JaFdBoH^&0b0)L%<M*$>XBpFUh5>p8+NZ&U
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pjmb~r2BsNyjW)DDg;|W6=mLS_$g#y%<0zJ+tqaMUWYN(x_74%>qC@}y

literal 0
HcmV?d00001

diff --git a/llvm/test/tools/dsymutil/Inputs/alias/foobar b/llvm/test/tools/dsymutil/Inputs/alias/foobar
new file mode 100755
index 0000000000000000000000000000000000000000..8f3891decfde7dc75818fe94beab23f6c10b93bf
GIT binary patch
literal 8688
zcmeHNOKTHR6h32H6s@)>h+-k56!8HW7Zo3?MiNYY)T$|HMQ)SMlm?qLBol3S0dXN(
z=+d427rJ+$8|iNl6x;~z1QGH3=F!YVrQ%LJ2hKhByZ4@R&-rFHckXO_{q%jih}9?3
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G9PtP4T$fV-

literal 0
HcmV?d00001

diff --git a/llvm/test/tools/dsymutil/X86/alias.test b/llvm/test/tools/dsymutil/X86/alias.test
new file mode 100644
index 0000000..9625b30
--- /dev/null
+++ b/llvm/test/tools/dsymutil/X86/alias.test
@@ -0,0 +1,19 @@
+# RUN: llvm-dsymutil -f -oso-prepend-path=%p/../Inputs/alias \
+# RUN: %p/../Inputs/alias/foobar -o - 2>&1 | llvm-dwarfdump - | FileCheck %s
+# CHECK-NOT: could not find object file symbol for symbol
+# CHECK: DW_AT_name ("foo.c")
+# CHECK: DW_AT_name ("bar.c")
+
+# Source:
+#   $ cat foo.c
+#   int foo = 1;
+#   $ cat bar.c
+#   extern int bar;
+#   int main() {
+#     return bar;
+#   }
+
+# Compile with:
+#   $ clang -g -O0 bar.c -c -o bar.o
+#   $ clang -g -O0 foo.c -c -o foo.o
+#   $ ld -arch x86_64 -macosx_version_min 10.13.0 foo.o bar.o -lSystem -alias _foo _bar -o foobar
diff --git a/llvm/tools/dsymutil/MachODebugMapParser.cpp b/llvm/tools/dsymutil/MachODebugMapParser.cpp
index 75ae67c..866196f 100644
--- a/llvm/tools/dsymutil/MachODebugMapParser.cpp
+++ b/llvm/tools/dsymutil/MachODebugMapParser.cpp
@@ -70,6 +70,7 @@ private:
                             sys::TimePoint<std::chrono::seconds> Timestamp);
   void resetParserState();
   uint64_t getMainBinarySymbolAddress(StringRef Name);
+  std::vector<StringRef> getMainBinarySymbolNames(uint64_t Value);
   void loadMainBinarySymbols(const MachOObjectFile &MainBinary);
   void loadCurrentObjectFileSymbols(const object::MachOObjectFile &Obj);
   void handleStabSymbolTableEntry(uint32_t StringIndex, uint8_t Type,
@@ -382,9 +383,21 @@ void MachODebugMapParser::handleStabSymbolTableEntry(uint32_t StringIndex,
   }
 
   auto ObjectSymIt = CurrentObjectAddresses.find(Name);
+
+  // If the name of a (non-static) symbol is not in the current object, we
+  // check all its aliases from the main binary.
+  if (ObjectSymIt == CurrentObjectAddresses.end() && Type != MachO::N_STSYM) {
+    for (const auto &Alias : getMainBinarySymbolNames(Value)) {
+      ObjectSymIt = CurrentObjectAddresses.find(Alias);
+      if (ObjectSymIt != CurrentObjectAddresses.end())
+        break;
+    }
+  }
+
   if (ObjectSymIt == CurrentObjectAddresses.end())
     return Warning("could not find object file symbol for symbol " +
                    Twine(Name));
+
   if (!CurrentDebugMapObject->addSymbol(Name, ObjectSymIt->getValue(), Value,
                                         Size))
     return Warning(Twine("failed to insert symbol '") + Name +
@@ -429,6 +442,17 @@ uint64_t MachODebugMapParser::getMainBinarySymbolAddress(StringRef Name) {
   return Sym->second;
 }
 
+/// Get all symbol names in the main binary for the given value.
+std::vector<StringRef>
+MachODebugMapParser::getMainBinarySymbolNames(uint64_t Value) {
+  std::vector<StringRef> Names;
+  for (const auto &Entry : MainBinarySymbolAddresses) {
+    if (Entry.second == Value)
+      Names.push_back(Entry.first());
+  }
+  return Names;
+}
+
 /// Load the interesting main binary symbols' addresses into
 /// MainBinarySymbolAddresses.
 void MachODebugMapParser::loadMainBinarySymbols(
-- 
2.7.4