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 4580 matching lines @@
     String move_full() {return std::move(first) + std::move(second);}
 };
 
 }  // unnamed namespace
 
 __attribute__ ((__visibility__("default")))
 extern "C"
 char*
 __cxa_demangle(const char* mangled_name, char* buf, size_t* n, int* status)
 {
+  // @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__
+  *status = 1;

[jvoung (off chromium), 2013/12/04 01:52:00]

The API says that status may be a null pointer (in which case the caller
wouldn't care about the status), so would be good to check first.

Also, it seems like the documented status values are 0, -1, -2, -3:
http://mentorembedded.github.io/cxx-abi/abi.html#demangler

Maybe do -1 and pretend that there is no memory for it?

[JF, 2013/12/04 02:10:25]

I fixed this and also moved the code down so it still does the checks below.

+  return 0;
+#else
+  // @LOCALMOD-END
     if (mangled_name == nullptr || (buf != nullptr && n == nullptr))
     {
         if (status)
             *status = invalid_args;
         return nullptr;
     }
     size_t internal_size = buf != nullptr ? *n : 0;
     arena<bs> a;
     struct Db
     {
@@ skipping 63 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