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

[Mehdi Amini via llvm-commits]

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@@ -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 StrRef;
+  raw_string_ostream RefOs(StrRef);
+#undef LDBG_STREAM
+#define LDBG_STREAM DebugOs
+#define DEBUG_TYPE "A"
+  LDBG() << "Hello, world!";
+  RefOs << "[A:1] " << __LLVM_FILE_NAME__ << ":" << (__LINE__ - 1)
+        << " Hello, world!\n";
+  EXPECT_EQ(DebugOs.str(), RefOs.str());
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joker-eph wrote:

DebugOS is where LDBG() is streaming. We generate the string we expect directly in RefOS, that is we construct the expected output of LDBG().
I could hardcode it but LDBG() depends on the current line number which makes it fragile.

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