extern-ify NullGuard's "(null)" strings to save linker input bytes.

PiperOrigin-RevId: 502689876
Change-Id: If75b00e2e257283b60c41411ef7a60dbd7cd8c6d

4 files changed, 47 insertions, 7 deletions

diff --git a/absl/log/CMakeLists.txt b/absl/log/CMakeLists.txt
index 91bba002..fb1b59f5 100644
--- a/absl/log/CMakeLists.txt
+++ b/absl/log/CMakeLists.txt
@@ -249,6 +249,7 @@ absl_cc_library(
   NAME
     log_internal_nullguard
   SRCS
+    "internal/nullguard.cc"
   HDRS
     "internal/nullguard.h"
   COPTS
@@ -257,6 +258,7 @@ absl_cc_library(
     ${ABSL_DEFAULT_LINKOPTS}
   DEPS
     absl::config
+    absl::core_headers
 )
 
 absl_cc_library(
diff --git a/absl/log/internal/BUILD.bazel b/absl/log/internal/BUILD.bazel
index 08276887..a1f1a67c 100644
--- a/absl/log/internal/BUILD.bazel
+++ b/absl/log/internal/BUILD.bazel
@@ -226,11 +226,13 @@ cc_library(
 
 cc_library(
     name = "nullguard",
+    srcs = ["nullguard.cc"],
     hdrs = ["nullguard.h"],
     copts = ABSL_DEFAULT_COPTS,
     linkopts = ABSL_DEFAULT_LINKOPTS,
     deps = [
         "//absl/base:config",
+        "//absl/base:core_headers",
     ],
 )
 
diff --git a/absl/log/internal/nullguard.cc b/absl/log/internal/nullguard.cc
new file mode 100644
index 00000000..7b785c55
--- /dev/null
+++ b/absl/log/internal/nullguard.cc
@@ -0,0 +1,35 @@
+// Copyright 2023 The Abseil Authors
+//
+// 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
+//
+//     https://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.
+
+#include "absl/log/internal/nullguard.h"
+
+#include <array>
+
+#include "absl/base/attributes.h"
+#include "absl/base/config.h"
+
+namespace absl {
+ABSL_NAMESPACE_BEGIN
+namespace log_internal {
+
+ABSL_CONST_INIT const std::array<char, 7> kCharNull{
+    {'(', 'n', 'u', 'l', 'l', ')', '\0'}};
+ABSL_CONST_INIT const std::array<signed char, 7> kSignedCharNull{
+    {'(', 'n', 'u', 'l', 'l', ')', '\0'}};
+ABSL_CONST_INIT const std::array<unsigned char, 7> kUnsignedCharNull{
+    {'(', 'n', 'u', 'l', 'l', ')', '\0'}};
+
+}  // namespace log_internal
+ABSL_NAMESPACE_END
+}  // namespace absl
diff --git a/absl/log/internal/nullguard.h b/absl/log/internal/nullguard.h
index 8ea38356..a0ed4ad7 100644
--- a/absl/log/internal/nullguard.h
+++ b/absl/log/internal/nullguard.h
@@ -27,26 +27,29 @@
 #include <array>
 #include <cstddef>
 
+#include "absl/base/attributes.h"
 #include "absl/base/config.h"
 
 namespace absl {
 ABSL_NAMESPACE_BEGIN
 namespace log_internal {
 
+ABSL_CONST_INIT extern const std::array<char, 7> kCharNull;
+ABSL_CONST_INIT extern const std::array<signed char, 7> kSignedCharNull;
+ABSL_CONST_INIT extern const std::array<unsigned char, 7> kUnsignedCharNull;
+
 template <typename T>
 struct NullGuard final {
   static const T& Guard(const T& v) { return v; }
 };
 template <>
 struct NullGuard<char*> final {
-  static const char* Guard(const char* v) { return v ? v : "(null)"; }
+  static const char* Guard(const char* v) { return v ? v : kCharNull.data(); }
 };
 template <>
 struct NullGuard<const char*> final {
-  static const char* Guard(const char* v) { return v ? v : "(null)"; }
+  static const char* Guard(const char* v) { return v ? v : kCharNull.data(); }
 };
-constexpr std::array<signed char, 7> kSignedCharNull{
-    {'(', 'n', 'u', 'l', 'l', ')', '\0'}};
 template <>
 struct NullGuard<signed char*> final {
   static const signed char* Guard(const signed char* v) {
@@ -59,8 +62,6 @@ struct NullGuard<const signed char*> final {
     return v ? v : kSignedCharNull.data();
   }
 };
-constexpr std::array<unsigned char, 7> kUnsignedCharNull{
-    {'(', 'n', 'u', 'l', 'l', ')', '\0'}};
 template <>
 struct NullGuard<unsigned char*> final {
   static const unsigned char* Guard(const unsigned char* v) {
@@ -75,7 +76,7 @@ struct NullGuard<const unsigned char*> final {
 };
 template <>
 struct NullGuard<std::nullptr_t> final {
-  static const char* Guard(const std::nullptr_t&) { return "(null)"; }
+  static const char* Guard(const std::nullptr_t&) { return kCharNull.data(); }
 };
 
 }  // namespace log_internal