From 55da426d44a14271457ae14c61e673b2c9ddc6fa Mon Sep 17 00:00:00 2001
From: frosch <frosch@openttd.org>
Date: Sun, 17 Sep 2023 00:33:35 +0200
Subject: [PATCH] Codechange: All ParagraphLayoutFactory::AppendToBuffer assume
 that the buffer has at least some space. Assert on that.

---
 src/gfx_layout_fallback.cpp       | 3 ++-
 src/gfx_layout_icu.cpp            | 1 +
 src/os/macosx/string_osx.h        | 1 +
 src/os/windows/string_uniscribe.h | 1 +
 4 files changed, 5 insertions(+), 1 deletion(-)

diff --git a/src/gfx_layout_fallback.cpp b/src/gfx_layout_fallback.cpp
index 1b3d020ac4..b44e874935 100644
--- a/src/gfx_layout_fallback.cpp
+++ b/src/gfx_layout_fallback.cpp
@@ -96,8 +96,9 @@ public:
  * @param c           The character to add.
  * @return The number of buffer spaces that were used.
  */
-/* static */ size_t FallbackParagraphLayoutFactory::AppendToBuffer(char32_t *buff, const char32_t *buffer_last, char32_t c)
+/* static */ size_t FallbackParagraphLayoutFactory::AppendToBuffer(char32_t *buff, [[maybe_unused]] const char32_t *buffer_last, char32_t c)
 {
+	assert(buff < buffer_last);
 	*buff = c;
 	return 1;
 }
diff --git a/src/gfx_layout_icu.cpp b/src/gfx_layout_icu.cpp
index a635c0c80c..981563c4d8 100644
--- a/src/gfx_layout_icu.cpp
+++ b/src/gfx_layout_icu.cpp
@@ -522,6 +522,7 @@ std::unique_ptr<const ICUParagraphLayout::Line> ICUParagraphLayout::NextLine(int
 
 /* static */ size_t ICUParagraphLayoutFactory::AppendToBuffer(UChar *buff, const UChar *buffer_last, char32_t c)
 {
+	assert(buff < buffer_last);
 	/* Transform from UTF-32 to internal ICU format of UTF-16. */
 	int32_t length = 0;
 	UErrorCode err = U_ZERO_ERROR;
diff --git a/src/os/macosx/string_osx.h b/src/os/macosx/string_osx.h
index 19c8ba5040..8fd9d988dc 100644
--- a/src/os/macosx/string_osx.h
+++ b/src/os/macosx/string_osx.h
@@ -63,6 +63,7 @@ public:
 	 */
 	static size_t AppendToBuffer(CharType *buff, const CharType *buffer_last, char32_t c)
 	{
+		assert(buff < buffer_last);
 		if (c >= 0x010000U) {
 			/* Character is encoded using surrogates in UTF-16. */
 			if (buff + 1 <= buffer_last) {
diff --git a/src/os/windows/string_uniscribe.h b/src/os/windows/string_uniscribe.h
index 56537be264..0c63d468c3 100644
--- a/src/os/windows/string_uniscribe.h
+++ b/src/os/windows/string_uniscribe.h
@@ -45,6 +45,7 @@ public:
 	*/
 	static size_t AppendToBuffer(CharType *buff, const CharType *buffer_last, char32_t c)
 	{
+		assert(buff < buffer_last);
 		if (c >= 0x010000U) {
 			/* Character is encoded using surrogates in UTF-16. */
 			if (buff + 1 <= buffer_last) {