| //===----------------------------------------------------------------------===// |
| // |
| // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. |
| // See https://llvm.org/LICENSE.txt for license information. |
| // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception |
| // |
| //===----------------------------------------------------------------------===// |
| |
| #ifndef _LIBCPP_REFSTRING_H |
| #define _LIBCPP_REFSTRING_H |
| |
| #include <__config> |
| #include <stdexcept> |
| #include <cstddef> |
| #include <cstring> |
| #include "atomic_support.h" |
| |
| // MacOS and iOS used to ship with libstdc++, and still support old applications |
| // linking against libstdc++. The libc++ and libstdc++ exceptions are supposed |
| // to be ABI compatible, such that they can be thrown from one library and caught |
| // in the other. |
| // |
| // For that reason, we must look for libstdc++ in the same process and if found, |
| // check the string stored in the exception object to see if it is the GCC empty |
| // string singleton before manipulating the reference count. This is done so that |
| // if an exception is created with a zero-length string in libstdc++, libc++abi |
| // won't try to delete the memory. |
| #if defined(__ENVIRONMENT_MAC_OS_X_VERSION_MIN_REQUIRED__) || \ |
| defined(__ENVIRONMENT_IPHONE_OS_VERSION_MIN_REQUIRED__) |
| # define _LIBCPP_CHECK_FOR_GCC_EMPTY_STRING_STORAGE |
| # include <dlfcn.h> |
| # include <mach-o/dyld.h> |
| #endif |
| |
| _LIBCPP_BEGIN_NAMESPACE_STD |
| |
| namespace __refstring_imp { namespace { |
| typedef int count_t; |
| |
| struct _Rep_base { |
| std::size_t len; |
| std::size_t cap; |
| count_t count; |
| }; |
| |
| inline _Rep_base* rep_from_data(const char *data_) noexcept { |
| char *data = const_cast<char *>(data_); |
| return reinterpret_cast<_Rep_base *>(data - sizeof(_Rep_base)); |
| } |
| |
| inline char * data_from_rep(_Rep_base *rep) noexcept { |
| char *data = reinterpret_cast<char *>(rep); |
| return data + sizeof(*rep); |
| } |
| |
| #if defined(_LIBCPP_CHECK_FOR_GCC_EMPTY_STRING_STORAGE) |
| inline |
| 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)); |
| } |
| |
| inline |
| const char* |
| get_gcc_empty_string_storage() noexcept |
| { |
| static const char* p = compute_gcc_empty_string_storage(); |
| return p; |
| } |
| #endif |
| |
| }} // namespace __refstring_imp |
| |
| using namespace __refstring_imp; |
| |
| inline |
| __libcpp_refstring::__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); |
| __imp_ = data; |
| } |
| |
| inline |
| __libcpp_refstring::__libcpp_refstring(const __libcpp_refstring &s) noexcept |
| : __imp_(s.__imp_) |
| { |
| if (__uses_refcount()) |
| __libcpp_atomic_add(&rep_from_data(__imp_)->count, 1); |
| } |
| |
| inline |
| __libcpp_refstring& __libcpp_refstring::operator=(__libcpp_refstring const& s) noexcept { |
| bool adjust_old_count = __uses_refcount(); |
| struct _Rep_base *old_rep = rep_from_data(__imp_); |
| __imp_ = s.__imp_; |
| if (__uses_refcount()) |
| __libcpp_atomic_add(&rep_from_data(__imp_)->count, 1); |
| if (adjust_old_count) |
| { |
| if (__libcpp_atomic_add(&old_rep->count, count_t(-1)) < 0) |
| { |
| ::operator delete(old_rep); |
| } |
| } |
| return *this; |
| } |
| |
| inline |
| __libcpp_refstring::~__libcpp_refstring() { |
| if (__uses_refcount()) { |
| _Rep_base* rep = rep_from_data(__imp_); |
| if (__libcpp_atomic_add(&rep->count, count_t(-1)) < 0) { |
| ::operator delete(rep); |
| } |
| } |
| } |
| |
| inline |
| bool __libcpp_refstring::__uses_refcount() const { |
| #if defined(_LIBCPP_CHECK_FOR_GCC_EMPTY_STRING_STORAGE) |
| return __imp_ != get_gcc_empty_string_storage(); |
| #else |
| return true; |
| #endif |
| } |
| |
| _LIBCPP_END_NAMESPACE_STD |
| |
| #endif //_LIBCPP_REFSTRING_H |