From fe480f5e29f212efd5b933475cc6e71fc5937f4d Mon Sep 17 00:00:00 2001
From: Benjamin Barenblat <bbaren@google.com>
Date: Tue, 6 Jul 2021 19:57:09 -0400
Subject: Add CHECK macro to logging framework

Reviewed-by: Alex Chernyakhovsky <achernya@google.com>
---
 buildconf/common.ninja |  3 ++-
 log.cc                 | 17 +++++++++++++++++
 log.h                  |  8 ++++++++
 log_test.cc            | 12 ++++++++++++
 4 files changed, 39 insertions(+), 1 deletion(-)
 create mode 100644 log.cc

diff --git a/buildconf/common.ninja b/buildconf/common.ninja
index 6ec7e96..e3d2298 100644
--- a/buildconf/common.ninja
+++ b/buildconf/common.ninja
@@ -30,8 +30,9 @@ rule link
 
 build gsrsup.o: cxx gsrsup.cc
 build gsrsup: link gsrsup.o
+build log.o: cxx log.cc
 build log_test.o: cxx log_test.cc
-build log_test: link log_test.o
+build log_test: link log.o log_test.o
   libs = -lgmock_main -lgmock -lgtest -labsl_strings -pthread
 
 default gsrsup
diff --git a/log.cc b/log.cc
new file mode 100644
index 0000000..13b74d7
--- /dev/null
+++ b/log.cc
@@ -0,0 +1,17 @@
+#include "log.h"
+
+#include <absl/strings/substitute.h>
+#include <stdlib.h>
+
+namespace gsrsup {
+
+void Check(Log& log, bool condition, const char* condition_str,
+           const char* file, int line) {
+  if (!condition) {
+    log.Error(absl::Substitute("internal error ($0:$1): ", file, line),
+              condition_str);
+    exit(1);
+  }
+}
+
+}  // namespace gsrsup
diff --git a/log.h b/log.h
index e0d3963..d588b8f 100644
--- a/log.h
+++ b/log.h
@@ -111,6 +111,14 @@ void Log::Message(Level level, Args... args) {
   out_->write(message.data(), message.size());
 }
 
+// If condition is false, logs an internal error and exits the program.
+void Check(Log& log, bool condition, const char* condition_str,
+           const char* file, int line);
+
 }  // namespace gsrsup
 
+// A convenience macro to invoke the Check function.
+#define CHECK(log, condition) \
+  ::gsrsup::Check((log), (condition), #condition, __FILE__, __LINE__)
+
 #endif  // GSRSUP_LOG_H_
diff --git a/log_test.cc b/log_test.cc
index 0ceb3f2..c06fd90 100644
--- a/log_test.cc
+++ b/log_test.cc
@@ -80,5 +80,17 @@ TEST(LogTest, DedicatedErrorFunction) {
   EXPECT_THAT(s.str(), HasSubstr("error:"));
 }
 
+TEST(LogTest, CheckPasses) {
+  std::ostringstream s;
+  Log log("program", s);
+  CHECK(log, 2 + 2 == 4);
+  EXPECT_THAT(s.str(), IsEmpty());
+}
+
+TEST(LogDeathTest, CheckFails) {
+  Log log("program", std::cerr);
+  EXPECT_DEATH(CHECK(log, 2 + 2 == 5), "internal error \\(.*\\): 2 \\+ 2 == 5");
+}
+
 }  // namespace
 }  // namespace gsrsup
-- 
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