Exceptions store the message as reference counted string for
compatibility to libstdc++. Move the implementation into a header for
easier sharing with libc++abi. Merge a number of improvements from that
version. Provide a POD definition for <stdexcept>'s public use to avoid
cast dances. Discussed with Marshall Clow.
git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@207695 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/include/__refstring b/include/__refstring
new file mode 100644
index 0000000..6866bf1
--- /dev/null
+++ b/include/__refstring
@@ -0,0 +1,139 @@
+//===------------------------ __refstring ---------------------------------===//
+//
+// 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.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef _LIBCPP___REFSTRING
+#define _LIBCPP___REFSTRING
+
+#include <__config>
+#include <cstddef>
+#include <cstring>
+#if __APPLE__
+#include <dlfcn.h>
+#include <mach-o/dyld.h>
+#endif
+
+_LIBCPP_BEGIN_NAMESPACE_STD
+
+class _LIBCPP_HIDDEN __libcpp_refstring
+{
+private:
+ const char* str_;
+
+ typedef int count_t;
+
+ struct _Rep_base
+ {
+ std::size_t len;
+ std::size_t cap;
+ count_t count;
+ };
+
+ static
+ _Rep_base*
+ rep_from_data(const char *data_) _NOEXCEPT
+ {
+ char *data = const_cast<char *>(data_);
+ return reinterpret_cast<_Rep_base *>(data - sizeof(_Rep_base));
+ }
+ static
+ char *
+ data_from_rep(_Rep_base *rep) _NOEXCEPT
+ {
+ char *data = reinterpret_cast<char *>(rep);
+ return data + sizeof(*rep);
+ }
+
+#if __APPLE__
+ static
+ const char*
+ compute_gcc_empty_string_storage() _NOEXCEPT
+ {
+ void* handle = dlopen("/usr/lib/libstdc++.6.dylib", RTLD_NOLOAD);
+ if (handle == nullptr)
+ return nullptr;
+ void* sym = dlsym(handle, "_ZNSs4_Rep20_S_empty_rep_storageE");
+ if (sym == nullptr)
+ return nullptr;
+ return data_from_rep(reinterpret_cast<_Rep_base *>(sym));
+ }
+
+ static
+ const char*
+ get_gcc_empty_string_storage() _NOEXCEPT
+ {
+ static const char* p = compute_gcc_empty_string_storage();
+ return p;
+ }
+
+ bool
+ uses_refcount() const
+ {
+ return str_ != get_gcc_empty_string_storage();
+ }
+#else
+ bool
+ uses_refcount() const
+ {
+ return true;
+ }
+#endif
+
+public:
+ explicit __libcpp_refstring(const char* msg) {
+ std::size_t len = strlen(msg);
+ _Rep_base* rep = static_cast<_Rep_base *>(::operator new(sizeof(*rep) + len + 1));
+ rep->len = len;
+ rep->cap = len;
+ rep->count = 0;
+ char *data = data_from_rep(rep);
+ std::memcpy(data, msg, len + 1);
+ str_ = data;
+ }
+
+ __libcpp_refstring(const __libcpp_refstring& s) _NOEXCEPT : str_(s.str_)
+ {
+ if (uses_refcount())
+ __sync_add_and_fetch(&rep_from_data(str_)->count, 1);
+ }
+
+ __libcpp_refstring& operator=(const __libcpp_refstring& s) _NOEXCEPT
+ {
+ bool adjust_old_count = uses_refcount();
+ struct _Rep_base *old_rep = rep_from_data(str_);
+ str_ = s.str_;
+ if (uses_refcount())
+ __sync_add_and_fetch(&rep_from_data(str_)->count, 1);
+ if (adjust_old_count)
+ {
+ if (__sync_add_and_fetch(&old_rep->count, count_t(-1)) < 0)
+ {
+ ::operator delete(old_rep);
+ }
+ }
+ return *this;
+ }
+
+ ~__libcpp_refstring()
+ {
+ if (uses_refcount())
+ {
+ _Rep_base* rep = rep_from_data(str_);
+ if (__sync_add_and_fetch(&rep->count, count_t(-1)) < 0)
+ {
+ ::operator delete(rep);
+ }
+ }
+ }
+
+ const char* c_str() const _NOEXCEPT {return str_;}
+};
+
+_LIBCPP_END_NAMESPACE_STD
+
+#endif //_LIBCPP___REFSTRING