[llvm][support] Add LDBG macro. (#143704)

Add macro that mirror a common usage of logging to output .This makes it easy to have
streaming log like behavior while still using the base debug logging.

I also wanted to avoid inventing a full logging library here while enabling others to change the sink without too much pain, so put it in its own header (this also avoids making Debug depend on raw_ostream beyond forward reference). The should allow a consistent dev experience without fixing the sink too much.

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Co-authored-by: Mehdi Amini <joker.eph@gmail.com>

1 files changed, 77 insertions, 0 deletions

diff --git a/llvm/unittests/Support/DebugLogTest.cpp b/llvm/unittests/Support/DebugLogTest.cpp
new file mode 100644
index 0000000..5136999
--- /dev/null
+++ b/llvm/unittests/Support/DebugLogTest.cpp
@@ -0,0 +1,77 @@
+//===- llvm/unittest/Support/DebugLogTest.cpp -----------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#include "llvm/Support/DebugLog.h"
+#include "llvm/Support/raw_ostream.h"
+#include "gmock/gmock.h"
+#include "gtest/gtest.h"
+
+#include <string>
+using namespace llvm;
+using testing::Eq;
+using testing::HasSubstr;
+
+#ifndef NDEBUG
+TEST(DebugLogTest, Basic) {
+  llvm::DebugFlag = true;
+  static const char *DT[] = {"A", "B"};
+
+  // Clear debug types.
+  setCurrentDebugTypes(DT, 0);
+  {
+    std::string str;
+    raw_string_ostream os(str);
+    DEBUGLOG_WITH_STREAM_AND_TYPE(os, nullptr) << "NoType";
+    EXPECT_TRUE(StringRef(os.str()).starts_with('['));
+    EXPECT_TRUE(StringRef(os.str()).ends_with("NoType\n"));
+  }
+
+  setCurrentDebugTypes(DT, 2);
+  {
+    std::string str;
+    raw_string_ostream os(str);
+    DEBUGLOG_WITH_STREAM_AND_TYPE(os, "A") << "A";
+    DEBUGLOG_WITH_STREAM_AND_TYPE(os, "B") << "B";
+    EXPECT_THAT(os.str(), AllOf(HasSubstr("A\n"), HasSubstr("B\n")));
+  }
+
+  setCurrentDebugType("A");
+  {
+    std::string str;
+    raw_string_ostream os(str);
+    // Just check that the macro doesn't result in dangling else.
+    if (true)
+      DEBUGLOG_WITH_STREAM_AND_TYPE(os, "A") << "A";
+    else
+      DEBUGLOG_WITH_STREAM_AND_TYPE(os, "A") << "B";
+    DEBUGLOG_WITH_STREAM_AND_TYPE(os, "B") << "B";
+    EXPECT_THAT(os.str(), AllOf(HasSubstr("A\n"), Not(HasSubstr("B\n"))));
+
+    int count = 0;
+    auto inc = [&]() { return ++count; };
+    EXPECT_THAT(count, Eq(0));
+    DEBUGLOG_WITH_STREAM_AND_TYPE(os, "A") << inc();
+    EXPECT_THAT(count, Eq(1));
+    DEBUGLOG_WITH_STREAM_AND_TYPE(os, "B") << inc();
+    EXPECT_THAT(count, Eq(1));
+  }
+}
+#else
+TEST(DebugLogTest, Basic) {
+  // LDBG should be compiled out in NDEBUG, so just check it compiles and has
+  // no effect.
+  llvm::DebugFlag = true;
+  static const char *DT[] = {};
+  setCurrentDebugTypes(DT, 0);
+  int count = 0;
+  auto inc = [&]() { return ++count; };
+  EXPECT_THAT(count, Eq(0));
+  LDBG() << inc();
+  EXPECT_THAT(count, Eq(0));
+}
+#endif