Initial support for dumping DWARF corresponding to Swift code

src/common/language.cc

Index: src/common/language.cc
diff --git a/src/common/language.cc b/src/common/language.cc
index c2fd81f644c21ced2abbffba67a829b3bf721db5..efadd35fad2216eb9b5a0472d2be31e607fa072c 100644
--- a/src/common/language.cc
+++ b/src/common/language.cc
@@ -34,18 +34,61 @@
 
 #include "common/language.h"
 
+#include <stdlib.h>
+
+#if !defined(__ANDROID__)
+#include <cxxabi.h>
+#endif
+
+#include <limits>
+
+namespace {
+
+string MakeQualifiedNameWithSeparator(const string& parent_name,
+                                      const char* separator,
+                                      const string& name) {
+  if (parent_name.empty()) {
+    return name;
+  }
+
+  return parent_name + separator + name;
+}
+
+}  // namespace
+
 namespace google_breakpad {
 
+const int Language::kDontDemangle = std::numeric_limits<int>::min();
+
 // C++ language-specific operations.
 class CPPLanguage: public Language {
  public:
   CPPLanguage() {}
+
   string MakeQualifiedName(const string &parent_name,
                            const string &name) const {
-    if (parent_name.empty())
-      return name;
-    else
-      return parent_name + "::" + name;
+    return MakeQualifiedNameWithSeparator(parent_name, "::", name);
+  }
+
+  virtual int DemangleName(const string& mangled, std::string* demangled)
+      const {
+    char* demangled_c = NULL;
+    int status = kDontDemangle;
+#if !defined(__ANDROID__)  // Android NDK doesn't provide abi::__cxa_demangle.
+    demangled_c = abi::__cxa_demangle(mangled.c_str(), NULL, NULL, &status);
+#endif

[Ted Mielczarek, 2016/09/14 10:20:10]

This seems like it'd be clearer to read if it was just:
#if defined(__ANDROID__)
  return whatever;
#else
  // actually try to demangle
#endif

+
+    if (status != 0) {
+      demangled->clear();
+    } else {
+      demangled->assign(demangled_c);
+    }
+
+    if (demangled_c) {
+      free(reinterpret_cast<void*>(demangled_c));
+    }
+
+    return status;
   }
 };
 
@@ -54,19 +97,45 @@ CPPLanguage CPPLanguageSingleton;
 // Java language-specific operations.
 class JavaLanguage: public Language {
  public:
+  JavaLanguage() {}
+
   string MakeQualifiedName(const string &parent_name,
                            const string &name) const {
-    if (parent_name.empty())
-      return name;
-    else
-      return parent_name + "." + name;
+    return MakeQualifiedNameWithSeparator(parent_name, ".", name);
   }
 };
 
 JavaLanguage JavaLanguageSingleton;
 
+// Swift language-specific operations.
+class SwiftLanguage: public Language {
+ public:
+  SwiftLanguage() {}
+
+  string MakeQualifiedName(const string &parent_name,
+                           const string &name) const {
+    return MakeQualifiedNameWithSeparator(parent_name, ".", name);
+  }
+
+  virtual int DemangleName(const string& mangled, std::string* demangled)
+      const {
+    // There is no programmatic interface to a Swift demangler. Pass through the
+    // mangled form because it encodes more information than the qualified name
+    // that would have been built by MakeQualifiedName(). The output can be
+    // post-processed by xcrun swift-demangle to transform mangled Swift names
+    // into something more readable.
+    demangled->assign(mangled);
+    return 0;
+  }
+};
+
+SwiftLanguage SwiftLanguageSingleton;
+
 // Assembler language-specific operations.
 class AssemblerLanguage: public Language {
+ public:
+  AssemblerLanguage() {}
+
   bool HasFunctions() const { return false; }
   string MakeQualifiedName(const string &parent_name,
                            const string &name) const {
@@ -78,6 +147,7 @@ AssemblerLanguage AssemblerLanguageSingleton;
 
 const Language * const Language::CPlusPlus = &CPPLanguageSingleton;
 const Language * const Language::Java = &JavaLanguageSingleton;
+const Language * const Language::Swift = &SwiftLanguageSingleton;
 const Language * const Language::Assembler = &AssemblerLanguageSingleton;
 
 } // namespace google_breakpad