From 649fe0fc8b9366375eab67639cab404617c527cd Mon Sep 17 00:00:00 2001
From: Victor Zverovich <viz@meta.com>
Date: Tue, 14 Nov 2023 07:48:10 -1000
Subject: [PATCH] Fix handling of null strings with the s specifier

---
 include/fmt/format.h | 7 ++++---
 test/format-test.cc  | 6 +++++-
 2 files changed, 9 insertions(+), 4 deletions(-)

diff --git a/include/fmt/format.h b/include/fmt/format.h
index 4104d91f..b84b6a5c 100644
--- a/include/fmt/format.h
+++ b/include/fmt/format.h
@@ -2342,9 +2342,10 @@ template <typename Char, typename OutputIt>
 FMT_CONSTEXPR auto write(OutputIt out, const Char* s,
                          const format_specs<Char>& specs, locale_ref)
     -> OutputIt {
-  return specs.type != presentation_type::pointer
-             ? write(out, basic_string_view<Char>(s), specs, {})
-             : write_ptr<Char>(out, bit_cast<uintptr_t>(s), &specs);
+  if (specs.type == presentation_type::pointer)
+    return write_ptr<Char>(out, bit_cast<uintptr_t>(s), &specs);
+  if (!s) throw_format_error("string pointer is null");
+  return write(out, basic_string_view<Char>(s), specs, {});
 }
 
 template <typename Char, typename OutputIt, typename T,
diff --git a/test/format-test.cc b/test/format-test.cc
index 9788c246..f4e7eeca 100644
--- a/test/format-test.cc
+++ b/test/format-test.cc
@@ -1531,8 +1531,12 @@ TEST(format_test, format_cstring) {
   EXPECT_EQ("test", fmt::format("{0:s}", "test"));
   char nonconst[] = "nonconst";
   EXPECT_EQ("nonconst", fmt::format("{0}", nonconst));
+  auto nullstr = static_cast<const char*>(nullptr);
   EXPECT_THROW_MSG(
-      (void)fmt::format(runtime("{0}"), static_cast<const char*>(nullptr)),
+      (void)fmt::format("{}", nullstr),
+      format_error, "string pointer is null");
+  EXPECT_THROW_MSG(
+      (void)fmt::format("{:s}", nullstr),
       format_error, "string pointer is null");
 }