Reduce binary size via format string compilation

Summary: Switch to format string compilation to prevent pulling in too many symbols from the {fmt} library into `folly/detail:ip_address`. This change saves ~64k (fixed cost) in opt mode compared to the current master or ~36k compared to the old code using Folly Format. This doesn't matter for server projects especially since {fmt} will likely be linked anyway but matters for some mobile ones.

Reviewed By: Orvid

Differential Revision: D25904078

fbshipit-source-id: 56473cf9bf4456a3cb3c5aa375c16393e144b6e1

folly/CompiledFormat.h

+/*
+ * Copyright (c) Facebook, Inc. and its affiliates.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#pragma once
+
+#include <fmt/compile.h>
+
+// Fallback to runtime format string processing for compatibility with fmt 6.x.
+#ifndef FMT_COMPILE
+#define FMT_COMPILE(format_str) format_str
+#endif

folly/File.cpp

@@ -16,8 +16,7 @@
 
 #include <folly/File.h>
 
-#include <fmt/core.h>
-
+#include <folly/CompiledFormat.h>
 #include <folly/Exception.h>
 #include <folly/FileUtil.h>
 #include <folly/ScopeGuard.h>
@@ -41,8 +40,8 @@ File::File(int fd, bool ownsFd) noexcept : fd_(fd), ownsFd_(ownsFd) {
 File::File(const char* name, int flags, mode_t mode)
     : fd_(::open(name, flags, mode)), ownsFd_(false) {
   if (fd_ == -1) {
-    throwSystemError(
-        fmt::format("open(\"{}\", {:#o}, 0{:#o}) failed", name, flags, mode));
+    throwSystemError(fmt::format(
+        FMT_COMPILE("open(\"{}\", {:#o}, 0{:#o}) failed"), name, flags, mode));
   }
   ownsFd_ = true;
 }

folly/Singleton.cpp

@@ -28,8 +28,7 @@
 #include <iostream>
 #include <string>
 
-#include <fmt/core.h>
-
+#include <folly/CompiledFormat.h>
 #include <folly/Demangle.h>
 #include <folly/ScopeGuard.h>
 #include <folly/detail/SingletonStackTrace.h>
@@ -159,8 +158,8 @@ void singletonPrintDestructionStackTrace(const TypeDescriptor& type) {
 }
 
 [[noreturn]] void singletonThrowNullCreator(const std::type_info& type) {
-  auto const msg = fmt::format(
-      "nullptr_t should be passed if you want {} to be default constructed",
+  auto const msg = fmt::format(FMT_COMPILE(
+      "nullptr_t should be passed if you want {} to be default constructed"),
       folly::StringPiece(demangle(type)));
   throw std::logic_error(msg);
 }

folly/detail/IPAddress.cpp

@@ -16,19 +16,20 @@
 
 #include <folly/detail/IPAddress.h>
 
-#include <fmt/core.h>
 #include <stdexcept>
 
+#include <folly/CompiledFormat.h>
+
 namespace folly {
 namespace detail {
 
 std::string familyNameStrDefault(sa_family_t family) {
-  return fmt::format("sa_family_t({})", family);
+  return fmt::format(FMT_COMPILE("sa_family_t({})"), family);
 }
 
 [[noreturn]] void getNthMSBitImplThrow(size_t bitCount, sa_family_t family) {
   throw std::invalid_argument(fmt::format(
-      "Bit index must be < {} for addresses of type: {}",
+      FMT_COMPILE("Bit index must be < {} for addresses of type: {}"),
       bitCount,
       familyNameStr(family)));
 }