update libcxxabi

1 files changed, 62 insertions, 15 deletions

diff --git a/system/lib/libcxxabi/src/stdexcept.cpp b/system/lib/libcxxabi/src/stdexcept.cpp
index 4aa962d0..de859db4 100644
--- a/system/lib/libcxxabi/src/stdexcept.cpp
+++ b/system/lib/libcxxabi/src/stdexcept.cpp
@@ -14,6 +14,11 @@
 #include <cstdint>
 #include <cstddef>
 
+#if __APPLE__
+#include <dlfcn.h>
+#include <mach-o/dyld.h>
+#endif
+
 // Note:  optimize for size
 
 #pragma GCC visibility push(hidden)
@@ -26,13 +31,39 @@ class __libcpp_nmstr
 private:
     const char* str_;
 
-    typedef std::size_t unused_t;
-    typedef std::int32_t count_t;
-
-    static const std::ptrdiff_t offset = static_cast<std::ptrdiff_t>(2*sizeof(unused_t) +
-                                                                       sizeof(count_t));
+    typedef int count_t;
+
+    struct _Rep_base
+    {
+        std::size_t len;
+        std::size_t cap;
+        count_t     count;
+    };
+
+    static const std::ptrdiff_t offset = static_cast<std::ptrdiff_t>(sizeof(_Rep_base));
+
+    count_t& count() const _NOEXCEPT {return ((_Rep_base*)(str_ - offset))->count;}
+
+#if __APPLE__
+    static
+    const void*
+    compute_gcc_empty_string_storage() _LIBCPP_CANTTHROW
+    {
+        void* handle = dlopen("/usr/lib/libstdc++.6.dylib", RTLD_NOLOAD);
+        if (handle == 0)
+            return 0;
+        return (const char*)dlsym(handle, "_ZNSs4_Rep20_S_empty_rep_storageE") + offset;
+    }
+    
+    static
+    const void*
+    get_gcc_empty_string_storage() _LIBCPP_CANTTHROW
+    {
+        static const void* p = compute_gcc_empty_string_storage();
+        return p;
+    }
+#endif
 
-    count_t& count() const _NOEXCEPT {return (count_t&)(*(str_ - sizeof(count_t)));}
 public:
     explicit __libcpp_nmstr(const char* msg);
     __libcpp_nmstr(const __libcpp_nmstr& s) _LIBCPP_CANTTHROW;
@@ -44,9 +75,9 @@ public:
 __libcpp_nmstr::__libcpp_nmstr(const char* msg)
 {
     std::size_t len = strlen(msg);
-    str_ = new char[len + 1 + offset];
-    unused_t* c = (unused_t*)str_;
-    c[0] = c[1] = len;
+    str_ = static_cast<const char*>(::operator new(len + 1 + offset));
+    _Rep_base* c = (_Rep_base*)str_;
+    c->len = c->cap = len;
     str_ += offset;
     count() = 0;
     std::strcpy(const_cast<char*>(c_str()), msg);
@@ -56,7 +87,10 @@ inline
 __libcpp_nmstr::__libcpp_nmstr(const __libcpp_nmstr& s)
     : str_(s.str_)
 {
-    __sync_add_and_fetch(&count(), 1);
+#if __APPLE__
+    if (str_ != get_gcc_empty_string_storage())
+#endif
+        __sync_add_and_fetch(&count(), 1);
 }
 
 __libcpp_nmstr&
@@ -64,17 +98,30 @@ __libcpp_nmstr::operator=(const __libcpp_nmstr& s)
 {
     const char* p = str_;
     str_ = s.str_;
-    __sync_add_and_fetch(&count(), 1);
-    if (__sync_add_and_fetch((count_t*)(p-sizeof(count_t)), -1) < 0)
-        delete [] (p-offset);
+#if __APPLE__
+    if (str_ != get_gcc_empty_string_storage())
+#endif
+        __sync_add_and_fetch(&count(), 1);
+#if __APPLE__
+    if (p != get_gcc_empty_string_storage())
+#endif
+        if (__sync_add_and_fetch((count_t*)(p-sizeof(count_t)), count_t(-1)) < 0)
+        {
+            ::operator delete(const_cast<char*>(p-offset));
+        }
     return *this;
 }
 
 inline
 __libcpp_nmstr::~__libcpp_nmstr()
 {
-    if (__sync_add_and_fetch(&count(), -1) < 0)
-        delete [] (str_ - offset);
+#if __APPLE__
+    if (str_ != get_gcc_empty_string_storage())
+#endif
+        if (__sync_add_and_fetch(&count(), count_t(-1)) < 0)
+        {
+            ::operator delete(const_cast<char*>(str_ - offset));
+        }
 }
 
 }