[libc-commits] [libc] [libc] Make 'printf' converter output "(null)" instead of "null" (PR #85845)

[Joseph Huber via libc-commits]

https://github.com/jhuber6 created https://github.com/llvm/llvm-project/pull/85845

Summary:
Currently we print `null` for the null pointer in a `%s` expression.
Although it's not defined by the standard, other implementations choose
to use `(null)` to indicate this. We also currently print `(nullptr)` so
I think it's more consistent to use parens in both cases.


>From 5c8d1b480cfb21dc899892d7f0df092f3dcd318c Mon Sep 17 00:00:00 2001
From: Joseph Huber <huberjn at outlook.com>
Date: Tue, 19 Mar 2024 13:38:40 -0500
Subject: [PATCH] [libc] Make 'printf' converter output "(null)" instead of
 "null"

Summary:
Currently we print `null` for the null pointer in a `%s` expression.
Although it's not defined by the standard, other implementations choose
to use `(null)` to indicate this. We also currently print `(nullptr)` so
I think it's more consistent to use parens in both cases.
---
 libc/src/stdio/printf_core/string_converter.h | 2 +-
 libc/test/src/stdio/sprintf_test.cpp          | 4 ++--
 2 files changed, 3 insertions(+), 3 deletions(-)

diff --git a/libc/src/stdio/printf_core/string_converter.h b/libc/src/stdio/printf_core/string_converter.h
index 04dc5a06da2226..9e05591079faa4 100644
--- a/libc/src/stdio/printf_core/string_converter.h
+++ b/libc/src/stdio/printf_core/string_converter.h
@@ -25,7 +25,7 @@ LIBC_INLINE int convert_string(Writer *writer, const FormatSection &to_conv) {
 
 #ifndef LIBC_COPT_PRINTF_NO_NULLPTR_CHECKS
   if (str_ptr == nullptr) {
-    str_ptr = "null";
+    str_ptr = "(null)";
   }
 #endif // LIBC_COPT_PRINTF_NO_NULLPTR_CHECKS
 
diff --git a/libc/test/src/stdio/sprintf_test.cpp b/libc/test/src/stdio/sprintf_test.cpp
index ab8bdb23b1187c..8dde95d02a96dc 100644
--- a/libc/test/src/stdio/sprintf_test.cpp
+++ b/libc/test/src/stdio/sprintf_test.cpp
@@ -121,8 +121,8 @@ TEST(LlvmLibcSPrintfTest, StringConv) {
 
 #ifndef LIBC_COPT_PRINTF_NO_NULLPTR_CHECKS
   written = LIBC_NAMESPACE::sprintf(buff, "%s", nullptr);
-  EXPECT_EQ(written, 4);
-  ASSERT_STREQ(buff, "null");
+  EXPECT_EQ(written, 6);
+  ASSERT_STREQ(buff, "(null)");
 #endif // LIBC_COPT_PRINTF_NO_NULLPTR_CHECKS
 }