From 7b04bdf491bc661fd508d33aa1d4e650c50e9811 Mon Sep 17 00:00:00 2001
From: Thiago Macieira <thiago.macieira@intel.com>
Date: Fri, 19 Jan 2024 08:10:38 -0800
Subject: [PATCH] CPlusPlus: deal with QByteArray::(c)begin() return nullptr

You should either use begin() and end(), or data() and size(), and
either way you shouldn't dereference the first iterator if the size is
zero.

Roberto's parser in 3rdparty/cplusplus assumes you've passed at least
one character (I'm guessing the null terminator) and does pointer
manipulation there:

void Lexer::setSource(const char *firstChar, const char *lastChar)
{
    _firstChar = firstChar;
    _lastChar = lastChar;
    _currentChar = _firstChar - 1;
    _currentCharUtf16 = ~0;
    _tokenStart = _currentChar;
    _yychar = '\n';
}

Note the _firstChar - 1 math is technically UB if firstChar is the
actual first character of any buffer allocation or string.

Fixes: QTCREATORBUG-30044
Change-Id: I76ffba14ece04f24b43efffd17abcb8102497813
Reviewed-by: Christian Kandeler <christian.kandeler@qt.io>
---
 src/libs/3rdparty/cplusplus/TranslationUnit.cpp | 2 ++
 src/libs/cplusplus/CppDocument.cpp              | 2 +-
 2 files changed, 3 insertions(+), 1 deletion(-)

diff --git a/src/libs/3rdparty/cplusplus/TranslationUnit.cpp b/src/libs/3rdparty/cplusplus/TranslationUnit.cpp
index 848f61285cb..e680ee2660e 100644
--- a/src/libs/3rdparty/cplusplus/TranslationUnit.cpp
+++ b/src/libs/3rdparty/cplusplus/TranslationUnit.cpp
@@ -27,6 +27,7 @@
 #include "Literals.h"
 #include "DiagnosticClient.h"
 
+#include "cppassert.h"
 #include <utils/textutils.h>
 
 #include <stack>
@@ -87,6 +88,7 @@ int TranslationUnit::sourceLength() const
 
 void TranslationUnit::setSource(const char *source, int size)
 {
+    CPP_CHECK(source);
     _firstSourceChar = source;
     _lastSourceChar = source + size;
 }
diff --git a/src/libs/cplusplus/CppDocument.cpp b/src/libs/cplusplus/CppDocument.cpp
index 6dc59bf1bf1..c7454589aa7 100644
--- a/src/libs/cplusplus/CppDocument.cpp
+++ b/src/libs/cplusplus/CppDocument.cpp
@@ -527,7 +527,7 @@ Document::Ptr Document::create(const FilePath &filePath)
 void Document::setUtf8Source(const QByteArray &source)
 {
     _source = source;
-    _translationUnit->setSource(_source.constBegin(), _source.size());
+    _translationUnit->setSource(_source.constData(), _source.size());
 }
 
 LanguageFeatures Document::languageFeatures() const