src/common/format.hpp

   1 /*
   2  * Copyright (C) 2022 Jérémie Galarneau <jeremie.galarneau@efficios.com>
   3  *
   4  * SPDX-License-Identifier: LGPL-2.1-only
   5  *
   6  */
   7 #ifndef LTTNG_FORMAT_H
   8 #define LTTNG_FORMAT_H
   9
  10 #include <common/macros.hpp>
  11
  12 #include <cxxabi.h>
  13 #include <string>
  14 #include <utility>
  15
  16 DIAGNOSTIC_PUSH
  17 DIAGNOSTIC_IGNORE_SUGGEST_ATTRIBUTE_FORMAT
  18 DIAGNOSTIC_IGNORE_DUPLICATED_BRANCHES
  19 #define FMT_HEADER_ONLY
  20 #include <vendor/fmt/core.h>
  21 DIAGNOSTIC_POP
  22
  23 #include <common/make-unique-wrapper.hpp>
  24
  25 /*
  26  * Due to a bug in g++ < 7.1, this specialization must be enclosed in the fmt namespace,
  27  * see https://gcc.gnu.org/bugzilla/show_bug.cgi?id=56480.
  28  */
  29 namespace fmt {
  30 template <>
  31 struct formatter<std::type_info> : formatter<std::string> {
  32         template <typename FormatContextType>
  33         typename FormatContextType::iterator format(const std::type_info& type_info,
  34                                                     FormatContextType& ctx)
  35         {
  36                 int status;
  37                 /*
  38                  * The documentation of __cxa_demangle mentions the returned string is allocated
  39                  * using malloc (not new), hence the use of lttng::free.
  40                  */
  41                 const auto demangled_name = lttng::make_unique_wrapper<char, lttng::free>(
  42                         abi::__cxa_demangle(type_info.name(), nullptr, nullptr, &status));
  43
  44                 auto it = status == 0 ? formatter<std::string>::format(demangled_name.get(), ctx) :
  45                                         formatter<std::string>::format(type_info.name(), ctx);
  46                 return it;
  47         }
  48 };
  49 } /* namespace fmt */
  50
  51 namespace lttng {
  52 template <typename... FormattingArguments>
  53 std::string format(FormattingArguments&&...args)
  54 {
  55         try {
  56                 return fmt::format(std::forward<FormattingArguments>(args)...);
  57         } catch (const fmt::format_error& ex) {
  58                 return std::string("Failed to format string: ") += ex.what();
  59         }
  60 }
  61 } /* namespace lttng */
  62
  63 #endif /* LTTNG_FORMAT_H */