From 884086ba763a8794a00ef5cd4c2a86c064ce8394 Mon Sep 17 00:00:00 2001
From: Stenzek <stenzek@gmail.com>
Date: Wed, 24 May 2023 19:34:04 +1000
Subject: [PATCH] StringUtil: Fix incorrect value of endptr

And add associated unit tests.
---
 common/StringUtil.h                      | 10 ++-----
 tests/ctest/common/string_util_tests.cpp | 33 ++++++++++++++++++++++++
 2 files changed, 35 insertions(+), 8 deletions(-)

diff --git a/common/StringUtil.h b/common/StringUtil.h
index e0195b2c10..4b93490617 100644
--- a/common/StringUtil.h
+++ b/common/StringUtil.h
@@ -100,10 +100,7 @@ namespace StringUtil
 			return std::nullopt;
 
 		if (endptr)
-		{
-			const size_t remaining_len = end - ptr - 1;
-			*endptr = (remaining_len > 0) ? std::string_view(result.ptr, remaining_len) : std::string_view();
-		}
+			*endptr = (result.ptr < end) ? std::string_view(result.ptr, end - result.ptr) : std::string_view();
 
 		return value;
 	}
@@ -131,10 +128,7 @@ namespace StringUtil
 			return std::nullopt;
 
 		if (endptr)
-		{
-			const size_t remaining_len = end - ptr - 1;
-			*endptr = (remaining_len > 0) ? std::string_view(result.ptr, remaining_len) : std::string_view();
-		}
+			*endptr = (result.ptr < end) ? std::string_view(result.ptr, end - result.ptr) : std::string_view();
 
 		return value;
 	}
diff --git a/tests/ctest/common/string_util_tests.cpp b/tests/ctest/common/string_util_tests.cpp
index b7b788772b..6bc40a535f 100644
--- a/tests/ctest/common/string_util_tests.cpp
+++ b/tests/ctest/common/string_util_tests.cpp
@@ -43,6 +43,39 @@ TEST(StringUtil, FromChars)
 	ASSERT_EQ(StringUtil::FromChars<int>("ff", 16).value_or(0), 255);
 }
 
+TEST(StringUtil, FromCharsWithEndPtr)
+{
+	using namespace std::literals;
+
+	std::string_view endptr;
+	ASSERT_EQ(StringUtil::FromChars<u32>("123x456", 16, &endptr), std::optional<u32>(0x123));
+	ASSERT_EQ(endptr, "x456"sv);
+
+	ASSERT_EQ(StringUtil::FromChars<u32>("0x1234", 16, &endptr), std::optional<u32>(0u));
+	ASSERT_EQ(endptr, "x1234"sv);
+
+	ASSERT_EQ(StringUtil::FromChars<u32>("1234", 16, &endptr), std::optional<u32>(0x1234u));
+	ASSERT_TRUE(endptr.empty());
+
+	ASSERT_EQ(StringUtil::FromChars<u32>("abcdefg", 16, &endptr), std::optional<u32>(0xabcdef));
+	ASSERT_EQ(endptr, "g"sv);
+
+	ASSERT_EQ(StringUtil::FromChars<u32>("123abc", 10, &endptr), std::optional<u32>(123));
+	ASSERT_EQ(endptr, "abc"sv);
+
+	ASSERT_EQ(StringUtil::FromChars<float>("1.0g", &endptr), std::optional<float>(1.0f));
+	ASSERT_EQ(endptr, "g"sv);
+
+	ASSERT_EQ(StringUtil::FromChars<float>("2x", &endptr), std::optional<float>(2.0f));
+	ASSERT_EQ(endptr, "x"sv);
+
+	ASSERT_EQ(StringUtil::FromChars<float>(".1p", &endptr), std::optional<float>(0.1f));
+	ASSERT_EQ(endptr, "p"sv);
+
+	ASSERT_EQ(StringUtil::FromChars<float>("1", &endptr), std::optional<float>(1.0f));
+	ASSERT_TRUE(endptr.empty());
+}
+
 #if 0
 // NOTE: These tests are disabled, because they require the da_DK locale to actually be present.
 // Which probably isn't going to be the case on the CI.