Don't ship a full C++ demangler as part of libc++abi

src/cxa_demangle.cpp

 //===-------------------------- cxa_demangle.cpp --------------------------===//
 //
 //                     The LLVM Compiler Infrastructure
 //
 // This file is dual licensed under the MIT and the University of Illinois Open
 // Source Licenses. See LICENSE.TXT for details.
 //
 //===----------------------------------------------------------------------===//
 
 #define _LIBCPP_EXTERN_TEMPLATE(...)
@@ skipping 4586 matching lines @@
 extern "C"
 char*
 __cxa_demangle(const char* mangled_name, char* buf, size_t* n, int* status)
 {
     if (mangled_name == nullptr || (buf != nullptr && n == nullptr))
     {
         if (status)
             *status = invalid_args;
         return nullptr;
     }
+    // @LOCALMOD-START The demangler is *huge* and only used in
+    // default_terminate_handler with a fallback to printing mangled
+    // names instead. pexe size matters a lot, so PNaCl only prints out
+    // mangled names when exceptions are uncaught.
+#ifdef __pnacl__
+    if (status)
+        *status = memory_alloc_failure;
+    return nullptr;
+#else
+    // @LOCALMOD-END
     size_t internal_size = buf != nullptr ? *n : 0;
     arena<bs> a;
     struct Db
     {
         typedef String String;
         typedef Vector<string_pair> sub_type;
         typedef Vector<sub_type> template_param_type;
         Vector<string_pair> names;
         Vector<sub_type> subs;
         Vector<template_param_type> template_param;
@@ skipping 57 matching lines @@
             db.names.back().first += db.names.back().second;
             std::memcpy(buf, db.names.back().first.data(), sz-1);
             buf[sz-1] = char(0);
         }
     }
     else
         buf = nullptr;
     if (status)
         *status = internal_status;
     return buf;
+    // @LOCALMOD-START
+#endif // __pnacl__
+    // @LOCALMOD-END
 }
 
 }  // __cxxabiv1