diff --git a/benchmark/CMakeLists.txt b/benchmark/CMakeLists.txt
index 0828b56..5d04019 100644
--- a/benchmark/CMakeLists.txt
+++ b/benchmark/CMakeLists.txt
@@ -29,4 +29,6 @@ file(GLOB HEAD_FILES ${LIBIPC_PROJECT_DIR}/benchmark/*.h)
 
 add_executable(${PROJECT_NAME} ${SRC_FILES} ${HEAD_FILES})
 
-target_link_libraries(${PROJECT_NAME} benchmark_main imp ipc)
+target_link_libraries(${PROJECT_NAME}
+  benchmark_main fmt
+  imp ipc)
diff --git a/include/libconcur/element.h b/include/libconcur/element.h
index b45dd28..f53381b 100644
--- a/include/libconcur/element.h
+++ b/include/libconcur/element.h
@@ -54,7 +54,7 @@ public:
     LIBIMP_TRY {
       data_ = std::forward<U>(src);
     } LIBIMP_CATCH(std::exception const &e) {
-      log.error("failed: `data = std::forward<U>(src)`. error = {}", e.what());
+      log.error("failed: `data = std::forward<U>(src)`. error = ", e.what());
     } LIBIMP_CATCH(...) {
       log.error("failed: `data = std::forward<U>(src)`. error = unknown");
     }
diff --git a/include/libimp/fmt.h b/include/libimp/fmt.h
index c35c68f..6e5dd9d 100644
--- a/include/libimp/fmt.h
+++ b/include/libimp/fmt.h
@@ -95,7 +95,7 @@ LIBIMP_EXPORT std::string to_string(long double a, span<char const> fstr = {}) n
 LIBIMP_EXPORT std::string to_string(std::nullptr_t) noexcept;
 template <typename T,
           typename = std::enable_if_t<std::is_same<T, void>::value>>
-LIBIMP_EXPORT std::string to_string(T *a) noexcept;
+LIBIMP_EXPORT std::string to_string(T const volatile *a) noexcept;
 
 /// @brief Date and time.
 LIBIMP_EXPORT std::string to_string(std::tm const &a, span<char const> fstr = {}) noexcept;
@@ -118,5 +118,11 @@ auto tag_invoke(fmt_to_string_t, T &&arg) noexcept
   return ::LIBIMP::to_string(std::forward<T>(arg));
 }
 
+template <typename T>
+auto tag_invoke(fmt_to_string_t, fmt_ref<T> arg) noexcept
+  -> decltype(::LIBIMP::to_string(static_cast<T>(arg.param), arg.fstr)) {
+  return ::LIBIMP::to_string(static_cast<T>(arg.param), arg.fstr);
+}
+
 } // namespace detail
 LIBIMP_NAMESPACE_END_
diff --git a/include/libimp/log.h b/include/libimp/log.h
index df9b794..43924ba 100644
--- a/include/libimp/log.h
+++ b/include/libimp/log.h
@@ -11,8 +11,6 @@
 #include <chrono>
 #include <exception>
 
-#include "fmt/format.h"
-
 #include "libimp/def.h"
 #include "libimp/detect_plat.h"
 #include "libimp/export.h"
@@ -40,9 +38,7 @@ struct context {
 
 LIBIMP_EXPORT std::string to_string(context &&) noexcept;
 
-/**
- * @brief Custom defined fmt_to_string method for imp::fmt
- */
+/// @brief Custom defined fmt_to_string method for imp::fmt
 template <typename T>
 std::string tag_invoke(decltype(::LIBIMP::fmt_to_string), context &&arg) noexcept {
   return ::LIBIMP::log::to_string(std::move(arg));
@@ -151,8 +147,8 @@ class grip {
   char const *func_;
   level level_limit_;
 
-  template <typename Fmt, typename... A>
-  grip &output(log::level l, Fmt &&ft, A &&... args) noexcept {
+  template <typename... A>
+  grip &output(log::level l, A &&... args) noexcept {
     if (!printer_ || (enum_cast(l) < enum_cast(level_limit_))) {
       return *this;
     }
@@ -160,7 +156,7 @@ class grip {
     LIBIMP_TRY {
       ctx = {
         l, std::chrono::system_clock::now(), func_,
-        ::fmt::format(std::forward<Fmt>(ft), std::forward<A>(args)...),
+        fmt(std::forward<A>(args)...),
       };
     } LIBIMP_CATCH(std::exception const &e) {
       /// @remark [TBD] std::string constructor may throw an exception
@@ -178,30 +174,12 @@ public:
     , func_       (func)
     , level_limit_(level_limit) {}
 
-  template <typename Fmt, typename... A>
-  grip &trace(Fmt &&ft, A &&... args) noexcept {
-    return output(log::level::trace, std::forward<Fmt>(ft), std::forward<A>(args)...);
-  }
-  template <typename Fmt, typename... A>
-  grip &debug(Fmt &&ft, A &&... args) noexcept {
-    return output(log::level::debug, std::forward<Fmt>(ft), std::forward<A>(args)...);
-  }
-  template <typename Fmt, typename... A>
-  grip &info(Fmt &&ft, A &&... args) noexcept {
-    return output(log::level::info, std::forward<Fmt>(ft), std::forward<A>(args)...);
-  }
-  template <typename Fmt, typename... A>
-  grip &warning(Fmt &&ft, A &&... args) noexcept {
-    return output(log::level::warning, std::forward<Fmt>(ft), std::forward<A>(args)...);
-  }
-  template <typename Fmt, typename... A>
-  grip &error(Fmt &&ft, A &&... args) noexcept {
-    return output(log::level::error, std::forward<Fmt>(ft), std::forward<A>(args)...);
-  }
-  template <typename Fmt, typename... A>
-  grip &failed(Fmt &&ft, A &&... args) noexcept {
-    return output(log::level::failed, std::forward<Fmt>(ft), std::forward<A>(args)...);
-  }
+  template <typename... A> grip &trace  (A &&...args) noexcept { return output(log::level::trace  , std::forward<A>(args)...); }
+  template <typename... A> grip &debug  (A &&...args) noexcept { return output(log::level::debug  , std::forward<A>(args)...); }
+  template <typename... A> grip &info   (A &&...args) noexcept { return output(log::level::info   , std::forward<A>(args)...); }
+  template <typename... A> grip &warning(A &&...args) noexcept { return output(log::level::warning, std::forward<A>(args)...); }
+  template <typename... A> grip &error  (A &&...args) noexcept { return output(log::level::error  , std::forward<A>(args)...); }
+  template <typename... A> grip &failed (A &&...args) noexcept { return output(log::level::failed , std::forward<A>(args)...); }
 };
 
 } // namespace log
diff --git a/include/libimp/result.h b/include/libimp/result.h
index 6037b30..8603d62 100644
--- a/include/libimp/result.h
+++ b/include/libimp/result.h
@@ -7,6 +7,7 @@
 #pragma once
 
 #include <type_traits>
+#include <string>
 #include <cstdint>
 
 #include "fmt/format.h"
@@ -14,6 +15,7 @@
 #include "libimp/def.h"
 #include "libimp/detect_plat.h"
 #include "libimp/export.h"
+#include "libimp/fmt.h"
 
 LIBIMP_NAMESPACE_BEG_
 
@@ -70,9 +72,12 @@ struct default_traits<T, std::enable_if_t<std::is_integral<T>::value>> {
   static T cast_from_code(result_type code) noexcept {
     return static_cast<T>(code);
   }
+  static std::string format(result<T> const &r) noexcept {
+    return fmt(*r);
+  }
   template <typename Out>
   static auto format(result<T> const &r, Out &&out) noexcept {
-    return format_to(out, "{}", *r);
+    return format_to(out, format(r));
   }
 };
 
@@ -86,12 +91,15 @@ struct default_traits<T, std::enable_if_t<std::is_pointer<T>::value>> {
   static T cast_from_code(result_type code) noexcept {
     return reinterpret_cast<T>(code);
   }
+  static std::string format(result<T> const &r) noexcept {
+    if LIBIMP_LIKELY(r) {
+      return fmt(static_cast<void *>(*r));
+    }
+    return fmt(static_cast<void *>(*r), ", code = ", r.code_value());
+  }
   template <typename Out>
   static auto format(result<T> const &r, Out &&out) noexcept {
-    if LIBIMP_LIKELY(r) {
-      return format_to(out, "{}", static_cast<void *>(*r));
-    }
-    return format_to(out, "{}, code = {}", static_cast<void *>(*r), r.code_value());
+    return format_to(out, format(r));
   }
 };
 
@@ -157,6 +165,19 @@ public:
   friend bool operator!=(result const &lhs, result const &rhs) noexcept { return lhs.code_ != rhs.code_; }
 };
 
+/// @brief Custom defined fmt_to_string method for imp::fmt
+namespace detail {
+
+inline std::string tag_invoke(decltype(::LIBIMP::fmt_to_string), result_code r) noexcept {
+  return fmt("[", (r ? "succ" : "fail"), ", value = ", *r, "]");
+}
+
+template <typename T, typename D>
+std::string tag_invoke(decltype(::LIBIMP::fmt_to_string), result<T, D> r) noexcept {
+  return fmt("[", (r ? "succ" : "fail"), ", value = ", result<T, D>::default_traits_t::format(r), "]");
+}
+
+} // namespace detail
 LIBIMP_NAMESPACE_END_
 
 template <typename T, typename D>
diff --git a/include/libimp/system.h b/include/libimp/system.h
index 435d257..ce207c6 100644
--- a/include/libimp/system.h
+++ b/include/libimp/system.h
@@ -13,6 +13,7 @@
 #include "libimp/def.h"
 #include "libimp/export.h"
 #include "libimp/result.h"
+#include "libimp/fmt.h"
 
 LIBIMP_NAMESPACE_BEG_
 namespace sys {
@@ -63,6 +64,13 @@ enum class info : std::int32_t {
 };
 LIBIMP_EXPORT result<std::int64_t> conf(info) noexcept;
 
+/**
+ * @brief @brief Custom defined fmt_to_string method for imp::fmt
+ */
+inline std::string tag_invoke(decltype(::LIBIMP::fmt_to_string), error r) noexcept {
+  return error_msg(r.code());
+}
+
 } // namespace sys
 LIBIMP_NAMESPACE_END_
 
diff --git a/src/libimp/fmt.cpp b/src/libimp/fmt.cpp
index 9db9e13..613f3ad 100644
--- a/src/libimp/fmt.cpp
+++ b/src/libimp/fmt.cpp
@@ -208,7 +208,7 @@ std::string to_string(std::nullptr_t) noexcept {
 }
 
 template <>
-std::string to_string<void, void>(void *a) noexcept {
+std::string to_string<void, void>(void const volatile *a) noexcept {
   if (a == nullptr) {
     return to_string(nullptr);
   }
diff --git a/src/libimp/log.cpp b/src/libimp/log.cpp
index 4bfc2f0..925fc46 100644
--- a/src/libimp/log.cpp
+++ b/src/libimp/log.cpp
@@ -3,8 +3,6 @@
 #include <utility>
 #include <cstdio>
 
-#include "fmt/chrono.h"
-
 LIBIMP_NAMESPACE_BEG_
 namespace log {
 
@@ -14,7 +12,7 @@ std::string to_string(context &&ctx) noexcept {
   };
   LIBIMP_TRY {
     auto ms = std::chrono::time_point_cast<std::chrono::milliseconds>(ctx.tp).time_since_epoch().count() % 1000;
-    return ::fmt::format("[{}][{:%Y-%m-%d %H:%M:%S}.{:03}][{}] {}", types[enum_cast(ctx.level)], ctx.tp, ms, ctx.func, ctx.text);
+    return fmt("[", types[enum_cast(ctx.level)], "][", ctx.tp, ".", spec("03")(ms), "][", ctx.func, "] ", ctx.text);
   } LIBIMP_CATCH(std::exception const &e) {
     /// @remark [TBD] std::string constructor may throw an exception
     return e.what();
diff --git a/src/libimp/platform/gnuc/demangle.h b/src/libimp/platform/gnuc/demangle.h
index e1ef540..f843f7b 100644
--- a/src/libimp/platform/gnuc/demangle.h
+++ b/src/libimp/platform/gnuc/demangle.h
@@ -29,7 +29,7 @@ std::string demangle(span<char const> name) noexcept {
   int status = 0;
   char *realname = abi::__cxa_demangle(name.data(), buffer, &sz, &status);
   if (realname == nullptr) {
-    log.error("failed: abi::__cxa_demangle(sz = {}), status = {}", sz, status);
+    log.error("failed: abi::__cxa_demangle(sz = ", sz, "), status = ", status);
     std::free(buffer);
     return {};
   }
diff --git a/src/libimp/platform/posix/system.h b/src/libimp/platform/posix/system.h
index b9ccd39..25e449d 100644
--- a/src/libimp/platform/posix/system.h
+++ b/src/libimp/platform/posix/system.h
@@ -46,8 +46,9 @@ std::string error_str(result_code code) noexcept {
 #if ((_POSIX_C_SOURCE >= 200112L || _XOPEN_SOURCE >= 600) && !_GNU_SOURCE)
   LIBIMP_LOG_();
   if (::strerror_r((int)code.value(), msg_buf, sizeof(msg_buf)) != 0) {
-    log.error("failed: strerror_r(code = {}, buf, buf-size = {}). error = {}", 
-             (int)code.value(), sizeof(msg_buf), error_code());
+    log.error("failed: strerror_r(code = ", (int)code.value(), 
+                      ", buf, buf-size = ", sizeof(msg_buf), 
+                      "). error = ", error_code());
     return {};
   }
   return msg_buf;
@@ -70,11 +71,11 @@ result<std::int64_t> conf(info r) noexcept {
     break;
   }
   default:
-    log.error("invalid info = {}", enum_cast(r));
+    log.error("invalid info = ", enum_cast(r));
     return {};
   }
   auto err = sys::error();
-  log.error("info = {}, error = {}", enum_cast(r), err);
+  log.error("info = ", enum_cast(r), ", error = ", err);
   return {false, (int)err.value()};
 }
 
diff --git a/src/libimp/platform/win/codecvt.h b/src/libimp/platform/win/codecvt.h
index abca909..edcb785 100644
--- a/src/libimp/platform/win/codecvt.h
+++ b/src/libimp/platform/win/codecvt.h
@@ -36,7 +36,7 @@ std::size_t cvt_cstr(char const *src, std::size_t slen, wchar_t *des, std::size_
   int cch_wc = (des == nullptr) ? 0 : (int)dlen;
   int size_needed = ::MultiByteToWideChar(CP_ACP, 0, src, (int)slen, des, cch_wc);
   if (size_needed <= 0) {
-    log.error("failed: MultiByteToWideChar(CP_ACP). error = {}", sys::error_code());
+    log.error("failed: MultiByteToWideChar(CP_ACP). error = ", sys::error_code());
   }
   return size_needed;
 }
@@ -51,7 +51,7 @@ std::size_t cvt_cstr(wchar_t const *src, std::size_t slen, char *des, std::size_
   int cb_mb = (des == nullptr) ? 0 : (int)dlen;
   int size_needed = ::WideCharToMultiByte(CP_ACP, 0, src, (int)slen, des, cb_mb, NULL, NULL);
   if (size_needed <= 0) {
-    log.error("failed: WideCharToMultiByte(CP_ACP). error = {}", sys::error_code());
+    log.error("failed: WideCharToMultiByte(CP_ACP). error = ", sys::error_code());
   }
   return size_needed;
 }
@@ -73,7 +73,7 @@ std::size_t cvt_cstr(char8_t const *src, std::size_t slen, wchar_t *des, std::si
   int cch_wc = (des == nullptr) ? 0 : (int)dlen;
   int size_needed = ::MultiByteToWideChar(CP_UTF8, 0, (char *)src, (int)slen, des, cch_wc);
   if (size_needed <= 0) {
-    log.error("failed: MultiByteToWideChar(CP_UTF8). error = {}", sys::error_code());
+    log.error("failed: MultiByteToWideChar(CP_UTF8). error = ", sys::error_code());
   }
   return size_needed;
 }
@@ -88,7 +88,7 @@ std::size_t cvt_cstr(wchar_t const *src, std::size_t slen, char8_t *des, std::si
   int cb_mb = (des == nullptr) ? 0 : (int)dlen;
   int size_needed = ::WideCharToMultiByte(CP_UTF8, 0, src, (int)slen, (char *)des, cb_mb, NULL, NULL);
   if (size_needed <= 0) {
-    log.error("failed: WideCharToMultiByte(CP_UTF8). error = {}", sys::error_code());
+    log.error("failed: WideCharToMultiByte(CP_UTF8). error = ", sys::error_code());
   }
   return size_needed;
 }
diff --git a/src/libimp/platform/win/system.h b/src/libimp/platform/win/system.h
index d8a199d..a24763a 100644
--- a/src/libimp/platform/win/system.h
+++ b/src/libimp/platform/win/system.h
@@ -59,7 +59,7 @@ std::string error_str(result_code code) noexcept {
           MAKELANGID(LANG_NEUTRAL, SUBLANG_DEFAULT),
           (LPTSTR)&lpErrText,
           0, NULL) == 0) {
-      log.error("failed: FormatMessage(dwMessageId = {}). error = {}", err, error_code());
+      log.error("failed: FormatMessage(dwMessageId = ", err, "). error = ", error_code());
       return {};
     }
     LIBIMP_UNUSED auto buf_guard = std::unique_ptr<std::remove_pointer_t<LPVOID>, 
@@ -94,7 +94,7 @@ result<std::int64_t> conf(info r) noexcept {
     return (std::int64_t)info.dwPageSize;
   }
   default:
-    log.error("invalid info = {}", enum_cast(r));
+    log.error("invalid info = ", enum_cast(r));
     return {};
   }
 }
diff --git a/src/libimp/system.cpp b/src/libimp/system.cpp
index b5b73dc..43d3972 100644
--- a/src/libimp/system.cpp
+++ b/src/libimp/system.cpp
@@ -1,6 +1,4 @@
 
-#include "fmt/format.h"
-
 #include "libimp/detect_plat.h"
 #if defined(LIBIMP_OS_WIN)
 # include "libimp/platform/win/system.h"
@@ -13,7 +11,7 @@ namespace sys {
 
 std::string error_msg(result_code code) noexcept {
   LIBIMP_TRY {
-    return ::fmt::format("[{}, \"{}\"]", code.value(), error_str(code));
+    return fmt("[", code.value(), ", \"", error_str(code), "\"]");
   } LIBIMP_CATCH(...) {
     return error_str(code);
   }
diff --git a/src/libipc/platform/posix/shm_impl.h b/src/libipc/platform/posix/shm_impl.h
index 366f53b..69955be 100644
--- a/src/libipc/platform/posix/shm_impl.h
+++ b/src/libipc/platform/posix/shm_impl.h
@@ -69,7 +69,7 @@ result<int> shm_open_fd(std::string const &name, mode::type type) noexcept {
     flag |= O_CREAT;
     break;
   default:
-    log.error("mode type is invalid. type = {}", type);
+    log.error("mode type is invalid. type = ", type);
     return {};
   }
 
@@ -84,7 +84,7 @@ result_code ftruncate_fd(int fd, std::size_t size) noexcept {
   /// @see https://man7.org/linux/man-pages/man3/ftruncate.3p.html
   if (::ftruncate(fd, size) != posix::succ) {
     auto err = sys::error();
-    log.error("failed: ftruncate({}, {}). error = {}", fd, size, err);
+    log.error("failed: ftruncate(", fd, ", ", size, "). error = ", err);
     return err.code();
   }
   return {posix::succ};
@@ -102,8 +102,9 @@ result<shm_t> shm_open(std::string name, std::size_t size, mode::type type) noex
   auto fd = shm_open_fd(name, type);
   if (!fd) return {};
   if (*fd == posix::failed) {
-    log.error("failed: shm_open(name = {}, type = {}). error = {}", 
-               name, type, sys::error());
+    log.error("failed: shm_open(name = ", name, 
+                             ", type = ", type, 
+                           "). error = ", sys::error());
     return {};
   }
   LIBIMP_UNUSED auto guard = std::unique_ptr<decltype(fd), void (*)(decltype(fd) *)> {
@@ -114,7 +115,7 @@ result<shm_t> shm_open(std::string name, std::size_t size, mode::type type) noex
   /// @brief Try to get the size of this fd
   struct stat st;
   if (::fstat(*fd, &st) == posix::failed) {
-    log.error("failed: fstat(fd = {}). error = {}", *fd, sys::error());
+    log.error("failed: fstat(fd = ", *fd, "). error = ", sys::error());
     return {};
   }
 
@@ -132,7 +133,7 @@ result<shm_t> shm_open(std::string name, std::size_t size, mode::type type) noex
   /// @brief Creates a new mapping in the virtual address space of the calling process.
   void *mem = ::mmap(nullptr, size, PROT_READ | PROT_WRITE, MAP_SHARED, *fd, 0);
   if (mem == MAP_FAILED) {
-    log.error("failed: mmap(size = {}, fd = {}). error = {}", size, *fd, sys::error());
+    log.error("failed: mmap(size = ", size, ", fd = ", *fd, "). error = ", sys::error());
     return {};
   }
   return new shm_handle{std::move(name), size, mem};
@@ -147,7 +148,7 @@ result_code shm_close(shm_t h) noexcept {
   if (shm == nullptr) return {};
   if (::munmap(shm->memp, shm->f_sz) == posix::failed) {
     auto err = sys::error();
-    log.error("failed: munmap({}, {}). error = {}", shm->memp, shm->f_sz, err);
+    log.error("failed: munmap(", shm->memp, ", ", shm->f_sz"). error = ", err);
     return err.code();
   }
   /// @brief no unlink the file.
diff --git a/src/libipc/platform/win/get_sa.h b/src/libipc/platform/win/get_sa.h
index 05887ee..3964188 100644
--- a/src/libipc/platform/win/get_sa.h
+++ b/src/libipc/platform/win/get_sa.h
@@ -30,11 +30,11 @@ inline LPSECURITY_ATTRIBUTES get_sa() {
       using namespace ::LIBIMP;
       log::grip log {"get_sa"};
       if (!::InitializeSecurityDescriptor(&sd_, SECURITY_DESCRIPTOR_REVISION)) {
-        log.error("failed: InitializeSecurityDescriptor(SECURITY_DESCRIPTOR_REVISION). error = {}", sys::error());
+        log.error("failed: InitializeSecurityDescriptor(SECURITY_DESCRIPTOR_REVISION). error = ", sys::error());
         return;
       }
       if (!::SetSecurityDescriptorDacl(&sd_, TRUE, NULL, FALSE)) {
-        log.error("failed: SetSecurityDescriptorDacl. error = {}", sys::error());
+        log.error("failed: SetSecurityDescriptorDacl. error = ", sys::error());
         return;
       }
       sa_.nLength = sizeof(SECURITY_ATTRIBUTES);
diff --git a/src/libipc/platform/win/mmap_impl.h b/src/libipc/platform/win/mmap_impl.h
index e7392ce..58623db 100644
--- a/src/libipc/platform/win/mmap_impl.h
+++ b/src/libipc/platform/win/mmap_impl.h
@@ -41,7 +41,7 @@ result_code mmap_close(HANDLE h) {
   }
   if (!::CloseHandle(h)) {
     auto err = sys::error();
-    log.error("failed: CloseHandle({}). error = {}", h, err);
+    log.error("failed: CloseHandle(", h, "). error = ", err);
     return err.code();
   }
   return {ERROR_SUCCESS};
@@ -77,7 +77,7 @@ result<HANDLE> mmap_open(std::string const &file, std::size_t size, mode::type t
     HANDLE h = ::OpenFileMapping(FILE_MAP_ALL_ACCESS, FALSE, t_name.c_str());
     if (h == NULL) {
       auto err = sys::error();
-      log.error("failed: OpenFileMapping(FILE_MAP_ALL_ACCESS, FALSE, {}). error = {}", file, err);
+      log.error("failed: OpenFileMapping(FILE_MAP_ALL_ACCESS, FALSE, ", file, "). error = ", err);
       return {nullptr, err.value()};
     }
     return h;
@@ -90,7 +90,7 @@ result<HANDLE> mmap_open(std::string const &file, std::size_t size, mode::type t
                                    0, static_cast<DWORD>(size), t_name.c_str());
     if (h == NULL) {
       auto err = sys::error();
-      log.error("failed: CreateFileMapping(PAGE_READWRITE | SEC_COMMIT, {}, {}). error = {}", size, file, err);
+      log.error("failed: CreateFileMapping(PAGE_READWRITE | SEC_COMMIT, ", size, ", ", file, "). error = ", err);
       return {nullptr, err.value()};
     }
     return h;
@@ -104,7 +104,7 @@ result<HANDLE> mmap_open(std::string const &file, std::size_t size, mode::type t
     ///      https://learn.microsoft.com/en-us/previous-versions/windows/embedded/aa517331(v=msdn.10)
     return try_open();
   } else if (!(type & mode::create)) {
-    log.error("mode type is invalid. type = {}", type);
+    log.error("mode type is invalid. type = ", type);
     return {};
   }
   auto h = try_create();
@@ -112,7 +112,7 @@ result<HANDLE> mmap_open(std::string const &file, std::size_t size, mode::type t
   /// @remark If the object exists before the function call, the function returns a handle to the existing object
   ///         (with its current size, not the specified size), and GetLastError returns ERROR_ALREADY_EXISTS.
   if ((type == mode::create) && (::GetLastError() == ERROR_ALREADY_EXISTS)) {
-    log.info("the file being created already exists. file = {}, type = {}", file, type);
+    log.info("the file being created already exists. file = ", file, ", type = ", type);
     mmap_close(*h);
     return {};
   }
@@ -132,7 +132,7 @@ result<LPVOID> mmap_memof(HANDLE h) {
   LPVOID mem = ::MapViewOfFile(h, FILE_MAP_ALL_ACCESS, 0, 0, 0);
   if (mem == NULL) {
     auto err = sys::error();
-    log.error("failed: MapViewOfFile({}, FILE_MAP_ALL_ACCESS). error = {}", h, err);
+    log.error("failed: MapViewOfFile(", h, ", FILE_MAP_ALL_ACCESS). error = ", err);
     return {nullptr, err.value()};
   }
   return mem;
@@ -151,7 +151,7 @@ result<SIZE_T> mmap_sizeof(LPCVOID mem) {
   MEMORY_BASIC_INFORMATION mem_info {};
   if (::VirtualQuery(mem, &mem_info, sizeof(mem_info)) == 0) {
     auto err = sys::error();
-    log.error("failed: VirtualQuery({}). error = {}", mem, err);
+    log.error("failed: VirtualQuery(", mem, "). error = ", err);
     return {false, (SIZE_T)err.value()};
   }
   return mem_info.RegionSize;
@@ -172,7 +172,7 @@ result_code mmap_release(HANDLE h, LPCVOID mem) {
     return {};
   }
   if (!::UnmapViewOfFile(mem)) {
-    log.warning("failed: UnmapViewOfFile. error = {}", sys::error());
+    log.warning("failed: UnmapViewOfFile. error = ", sys::error());
   }
   return mmap_close(h);
 }
diff --git a/src/libipc/platform/win/shm_impl.h b/src/libipc/platform/win/shm_impl.h
index d601908..897d94b 100644
--- a/src/libipc/platform/win/shm_impl.h
+++ b/src/libipc/platform/win/shm_impl.h
@@ -21,18 +21,18 @@ result<shm_t> shm_open(std::string name, std::size_t size, mode::type type) noex
   LIBIMP_LOG_();
   auto h = mmap_open(name, size, type);
   if (h == NULL) {
-    log.error("failed: mmap_open(name = {}, size = {}, type = {}).", name, size, type);
+    log.error("failed: mmap_open(name = ", name, ", size = ", size, ", type = ", type, ").");
     return {nullptr, h.code_value()};
   }
   auto mem = mmap_memof(*h);
   if (*mem == NULL) {
-    log.error("failed: mmap_memof({}).", *h);
+    log.error("failed: mmap_memof(", *h, ").");
     mmap_close(*h);
     return {nullptr, mem.code_value()};
   }
   auto sz = mmap_sizeof(*mem);
   if (!sz) {
-    log.error("failed: mmap_sizeof({}).", *mem);
+    log.error("failed: mmap_sizeof(", *mem, ").");
     mmap_close(*h);
     return {nullptr, static_cast<result_type>(sz.value())};
   }
diff --git a/src/libpmr/memory_resource.cpp b/src/libpmr/memory_resource.cpp
index 7824e5d..9b3b4cc 100644
--- a/src/libpmr/memory_resource.cpp
+++ b/src/libpmr/memory_resource.cpp
@@ -18,7 +18,7 @@ bool verify_args(::LIBIMP::log::grip &log, std::size_t bytes, std::size_t alignm
     return false;
   }
   if ((alignment == 0) || (alignment & (alignment - 1)) != 0) {
-    log.error("invalid bytes = {}, alignment = {}", bytes, alignment);
+    log.error("invalid bytes = ", bytes, ", alignment = ", alignment);
     return false;
   }
   return true;
@@ -66,8 +66,9 @@ void *new_delete_resource::allocate(std::size_t bytes, std::size_t alignment) no
   void *p = nullptr;
   int ret = ::posix_memalign(&p, alignment, bytes);
   if (ret != 0) {
-    log.error("failed: posix_memalign(alignment = {}, bytes = {}). error = {}", 
-               alignment, bytes, sys::error(ret));
+    log.error("failed: posix_memalign(alignment = ", alignment, 
+                                       ", bytes = ", bytes, 
+                                      "). error = ", sys::error(ret));
     return nullptr;
   }
   return p;
diff --git a/test/concur/test_concur_concurrent.cpp b/test/concur/test_concur_concurrent.cpp
index 18efc87..6c43930 100644
--- a/test/concur/test_concur_concurrent.cpp
+++ b/test/concur/test_concur_concurrent.cpp
@@ -93,7 +93,7 @@ namespace {
 template <typename PC>
 void test_concur(std::size_t np, std::size_t nc, std::size_t k) {
   LIBIMP_LOG_();
-  log.info("\n\tStart with: {}, {} producers, {} consumers...", imp::nameof<PC>(), np, nc);
+  log.info("\n\tStart with: ", imp::nameof<PC>(), ", ", np, " producers, ", nc, " consumers...");
 
   constexpr static std::uint32_t loop_size = 100'0000;
 
@@ -112,7 +112,7 @@ void test_concur(std::size_t np, std::size_t nc, std::size_t k) {
         std::this_thread::yield();
       }
       if (i % (loop_size / 10) == 0) {
-        log.info("[{}] put count: {}", n, i);
+        log.info("[", n, "] put count: ", i);
       }
     }
     --running;
diff --git a/test/imp/test_imp_result.cpp b/test/imp/test_imp_result.cpp
index 8230469..e79600f 100644
--- a/test/imp/test_imp_result.cpp
+++ b/test/imp/test_imp_result.cpp
@@ -69,13 +69,13 @@ TEST(result, fmt) {
     imp::result<int> r1 {false, -123};
     EXPECT_EQ(fmt::format("{}", r1), fmt::format("[fail, value = {}]", -123));
     imp::result<void *> r2 {&r1};
-    EXPECT_EQ(fmt::format("{}", r2), fmt::format("[succ, value = {}]", (void *)&r1));
+    EXPECT_EQ(fmt::format("{}", r2), imp::fmt("[succ, value = ", (void *)&r1, "]"));
     int aaa {};
     imp::result<int *> r3 {&aaa};
-    EXPECT_EQ(fmt::format("{}", r3), fmt::format("[succ, value = {}]", (void *)&aaa));
+    EXPECT_EQ(fmt::format("{}", r3), imp::fmt("[succ, value = ", (void *)&aaa, "]"));
     imp::result<int *> r4 {nullptr};
-    EXPECT_EQ(fmt::format("{}", r4), fmt::format("[fail, value = {}, code = 0]", nullptr));
+    EXPECT_EQ(fmt::format("{}", r4), imp::fmt("[fail, value = ", nullptr, ", code = 0]"));
     r4 = {nullptr, 1234};
-    EXPECT_EQ(fmt::format("{}", r4), fmt::format("[fail, value = {}, code = 1234]", nullptr));
+    EXPECT_EQ(fmt::format("{}", r4), imp::fmt("[fail, value = ", nullptr, ", code = 1234]"));
   }
 }
\ No newline at end of file