From 197cdd809226c02e074bb53d4e0c2db33dcfa3db Mon Sep 17 00:00:00 2001
From: "Alan M. Carroll" <amc@apache.org>
Date: Tue, 18 Dec 2018 14:36:22 -0600
Subject: [PATCH] BWF: Fix handling of null char * - avoid string_view
 constructor.

---
 include/tscore/BufferWriter.h                 | 27 ++++++++++++++++---
 .../unit_tests/test_BufferWriterFormat.cc     |  8 ++++++
 2 files changed, 32 insertions(+), 3 deletions(-)

diff --git a/include/tscore/BufferWriter.h b/include/tscore/BufferWriter.h
index 052a4de29cf..6da3e12c21b 100644
--- a/include/tscore/BufferWriter.h
+++ b/include/tscore/BufferWriter.h
@@ -704,12 +704,26 @@ BufferWriter::printv(BWFormat const &fmt, std::tuple<Args...> const &args)
   return *this;
 }
 
+// Must be first so that other inline formatters can use it.
+BufferWriter &bwformat(BufferWriter &w, BWFSpec const &spec, std::string_view sv);
+
 // Pointers that are not specialized.
 inline BufferWriter &
 bwformat(BufferWriter &w, BWFSpec const &spec, const void *ptr)
 {
   BWFSpec ptr_spec{spec};
   ptr_spec._radix_lead_p = true;
+
+  if (ptr == nullptr) {
+    if (spec._type == 's' || spec._type == 'S') {
+      ptr_spec._type = BWFSpec::DEFAULT_TYPE;
+      ptr_spec._ext  = ""_sv; // clear any extension.
+      return bwformat(w, spec, spec._type == 's' ? "null"_sv : "NULL"_sv);
+    } else if (spec._type == BWFSpec::DEFAULT_TYPE) {
+      return w; // print nothing if there is no format character override.
+    }
+  }
+
   if (ptr_spec._type == BWFSpec::DEFAULT_TYPE || ptr_spec._type == 'p') {
     ptr_spec._type = 'x'; // if default or 'p;, switch to lower hex.
   } else if (ptr_spec._type == 'P') {
@@ -723,7 +737,12 @@ BufferWriter &bwformat(BufferWriter &w, BWFSpec const &spec, MemSpan const &span
 
 // -- Common formatters --
 
-BufferWriter &bwformat(BufferWriter &w, BWFSpec const &spec, std::string_view sv);
+// Capture this explicitly so it doesn't go to any other pointer type.
+inline BufferWriter &
+bwformat(BufferWriter &w, BWFSpec const &spec, std::nullptr_t)
+{
+  return bwformat(w, spec, static_cast<void *>(nullptr));
+}
 
 template <size_t N>
 BufferWriter &
@@ -735,10 +754,12 @@ bwformat(BufferWriter &w, BWFSpec const &spec, const char (&a)[N])
 inline BufferWriter &
 bwformat(BufferWriter &w, BWFSpec const &spec, const char *v)
 {
-  if (spec._type == 'x' || spec._type == 'X') {
+  if (spec._type == 'x' || spec._type == 'X' || spec._type == 'p') {
     bwformat(w, spec, static_cast<const void *>(v));
-  } else {
+  } else if (v != nullptr) {
     bwformat(w, spec, std::string_view(v));
+  } else {
+    bwformat(w, spec, nullptr);
   }
   return w;
 }
diff --git a/src/tscore/unit_tests/test_BufferWriterFormat.cc b/src/tscore/unit_tests/test_BufferWriterFormat.cc
index e8dee671a08..1e3a70b8cca 100644
--- a/src/tscore/unit_tests/test_BufferWriterFormat.cc
+++ b/src/tscore/unit_tests/test_BufferWriterFormat.cc
@@ -306,6 +306,14 @@ TEST_CASE("bwstring", "[bwprint][bwstring]")
     ts::bwprint(out, fmt, std::string_view(), "Leif", "confused");
     REQUIRE(out == "Did you know? Leif is confused");
   }
+
+  char const *null_string{nullptr};
+  ts::bwprint(s, "Null {0:x}.{0}", null_string);
+  REQUIRE(s == "Null 0x0.");
+  ts::bwprint(s, "Null {0:X}.{0}", nullptr);
+  REQUIRE(s == "Null 0X0.");
+  ts::bwprint(s, "Null {0:p}.{0:P}.{0:s}.{0:S}", null_string);
+  REQUIRE(s == "Null 0x0.0X0.null.NULL");
 }
 
 TEST_CASE("BWFormat integral", "[bwprint][bwformat]")