dl_symbol_resolver.hpp

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// SPDX-FileCopyrightText: 2026 Jarosław Pelczar <jarek@jpelczar.com>
//
// SPDX-License-Identifier: BSD-2-Clause
 
#pragma once
 
#if !defined(__linux__) && !defined(__FreeBSD__) && !defined(__OpenBSD__) && !defined(__NetBSD__) &&                   \
    !defined(__DragonFly__)
#error "microfmt/inspector/dl_symbol_resolver.hpp only supports Linux and BSD systems"
#endif
 
#include <cstdint>
#include <dlfcn.h>
 
#include "../microfmt.hpp"
#include "symbol_resolver.hpp"
 
namespace microfmt::detail {
 
// decodes raw bytes of a target address space; casts, pointers and offsets are bounded by the explicit lengths checked
// here.
RELOCO_BEGIN_UNSAFE_CODE
inline bool dl_resolve_symbol(uintptr_t addr, raw_resolved_symbol &out_raw) noexcept {
  if (addr == 0)
    return false;
 
  Dl_info info{};
  // NOLINTNEXTLINE(performance-no-int-to-ptr)
  if (::dladdr(reinterpret_cast<const void *>(addr), &info) == 0 || info.dli_fbase == nullptr)
    return false;
 
  raw_resolved_symbol result{};
  result.image_name =
      (info.dli_fname != nullptr && info.dli_fname[0] != '\0') ? string_view(info.dli_fname) : string_view("");
  result.image_load_base = reinterpret_cast<uintptr_t>(info.dli_fbase);
 
  if (info.dli_sname != nullptr && info.dli_sname[0] != '\0' && info.dli_saddr != nullptr) {
    result.symbol_name = string_view(info.dli_sname);
    result.symbol_base = reinterpret_cast<uintptr_t>(info.dli_saddr);
    result.is_exact = (result.symbol_base == addr);
  }
 
  out_raw = result;
  return true;
}
RELOCO_END_UNSAFE_CODE
 
} // namespace microfmt::detail
 
namespace microfmt {
 
struct dl_symbol_resolver_tag {};
 
template <> struct symbol_resolver_traits<dl_symbol_resolver_tag> {
  using context_type = void;
 
  static bool resolve(uintptr_t addr, span<char>, raw_resolved_symbol &out_raw) noexcept {
    return detail::dl_resolve_symbol(addr, out_raw);
  }
};
 
} // namespace microfmt