[llvm] Introduce LDBG_OS() macro as a variant of LDBG() (PR #157194)

[Mehdi Amini via llvm-commits]

================
@@ -128,6 +128,131 @@ TEST(DebugLogTest, DestructorPrefix) {
   // After destructors, nothing should have been printed.
   EXPECT_EQ(os.str(), "");
 }
+
+TEST(DebugLogTest, LDBG_MACROS) {
+  llvm::DebugFlag = true;
+  static const char *DT[] = {"A:3", "B:2"};
+  setCurrentDebugTypes(DT, sizeof(DT) / sizeof(DT[0]));
+  std::string Str;
+  raw_string_ostream DebugOs(Str);
+  std::string StrExpected;
+  raw_string_ostream ExpectedOs(StrExpected);
+#undef LDBG_STREAM
+#define LDBG_STREAM DebugOs
+#define DEBUG_TYPE "A"
+  LDBG() << "Hello, world!";
+  ExpectedOs << "[A:1] " << __LLVM_FILE_NAME__ << ":" << (__LINE__ - 1)
+             << " Hello, world!\n";
+  EXPECT_EQ(DebugOs.str(), ExpectedOs.str());
+  Str.clear();
+  StrExpected.clear();
+
+  // Test with a level, no type.
+  LDBG(2) << "Hello, world!";
+  ExpectedOs << "[A:2] " << __LLVM_FILE_NAME__ << ":" << (__LINE__ - 1)
+             << " Hello, world!\n";
+  EXPECT_EQ(DebugOs.str(), ExpectedOs.str());
+  Str.clear();
+  StrExpected.clear();
+
+// Now the type will be explicit, check we don't use DEBUG_TYPE.
+#undef DEBUG_TYPE
+
+  // Test with a type
+  LDBG("B") << "Hello, world!";
----------------
joker-eph wrote:

That leads to a static_assert in LDBG_GET_DEFAULT_TYPE_OR_LEVEL

```
        static_assert(false, "DEBUG_TYPE is not defined");                     \
```

https://github.com/llvm/llvm-project/pull/157194