Highlighter: fix crash after context change

Context changes might delete rules. Make sure to not dereference
these deleted rules by:
- save needed rule information before context change
- untrack every rule in ProgressData that was deleted

Task-number: QTCREATORBUG-19916
Change-Id: Icdbb739c1030bf918dbbe6c3a540a7c8893ce5a9
Reviewed-by: Christian Stenger <christian.stenger@qt.io>

5 files changed, 26 insertions, 7 deletions

diff --git a/src/plugins/texteditor/generichighlighter/highlighter.cpp b/src/plugins/texteditor/generichighlighter/highlighter.cpp
index 2902f09a63..fd875eae28 100644
--- a/src/plugins/texteditor/generichighlighter/highlighter.cpp
+++ b/src/plugins/texteditor/generichighlighter/highlighter.cpp
@@ -372,29 +372,33 @@ void Highlighter::iterateThroughRules(const QString &text,
                 progress->clearBracesMatches();
             }
 
+            const QString itemData = rule->itemData();
+            const QSharedPointer<HighlightDefinition> definition = rule->definition();
+            const bool lookAhead = rule->isLookAhead();
             if (progress->isWillContinueLine()) {
                 createWillContinueBlock();
                 progress->setWillContinueLine(false);
             } else {
                 if (rule->hasChildren())
                     iterateThroughRules(text, length, progress, true, rule->children());
-
                 if (!rule->context().isEmpty() && contextChangeRequired(rule->context())) {
                     m_currentCaptures = progress->captures();
-                    changeContext(rule->context(), rule->definition());
+                    changeContext(rule->context(), definition);
                     contextChanged = true;
                 }
             }
 
+            // Do NOT access rule frome here on, because a context change might delete rule
+
             // Format is not applied to child rules directly (but relative to the offset of their
             // parent) nor to look ahead rules.
-            if (!childRule && !rule->isLookAhead()) {
-                if (rule->itemData().isEmpty())
+            if (!childRule && !lookAhead) {
+                if (itemData.isEmpty())
                     applyFormat(startOffset, progress->offset() - startOffset,
                                 m_currentContext->itemData(), m_currentContext->definition());
                 else
-                    applyFormat(startOffset, progress->offset() - startOffset, rule->itemData(),
-                                rule->definition());
+                    applyFormat(startOffset, progress->offset() - startOffset, itemData,
+                                definition);
             }
 
             // When there is a match of one child rule the others should be skipped. Otherwise
diff --git a/src/plugins/texteditor/generichighlighter/progressdata.cpp b/src/plugins/texteditor/generichighlighter/progressdata.cpp
index 6075a1a4e4..d79d5b0152 100644
--- a/src/plugins/texteditor/generichighlighter/progressdata.cpp
+++ b/src/plugins/texteditor/generichighlighter/progressdata.cpp
@@ -108,3 +108,8 @@ void ProgressData::trackRule(Rule *rule)
 {
     m_trackedRules.append(rule);
 }
+
+void ProgressData::unTrackRule(Rule *rule)
+{
+    m_trackedRules.removeAll(rule);
+}
diff --git a/src/plugins/texteditor/generichighlighter/progressdata.h b/src/plugins/texteditor/generichighlighter/progressdata.h
index 9563a1601e..d2b158146d 100644
--- a/src/plugins/texteditor/generichighlighter/progressdata.h
+++ b/src/plugins/texteditor/generichighlighter/progressdata.h
@@ -65,6 +65,7 @@ public:
     const QStringList &captures() const;
 
     void trackRule(Rule *rule);
+    void unTrackRule(Rule *rule);
 
 private:
     int m_offset;
diff --git a/src/plugins/texteditor/generichighlighter/specificrules.cpp b/src/plugins/texteditor/generichighlighter/specificrules.cpp
index 02e5ed4230..8c4b80dc66 100644
--- a/src/plugins/texteditor/generichighlighter/specificrules.cpp
+++ b/src/plugins/texteditor/generichighlighter/specificrules.cpp
@@ -172,6 +172,12 @@ bool StringDetectRule::doMatchSucceed(const QString &text,
 }
 
 // RegExpr
+RegExprRule::~RegExprRule()
+{
+    if (m_progress)
+        m_progress->unTrackRule(this);
+}
+
 void RegExprRule::setPattern(const QString &pattern)
 {
     if (pattern.startsWith(QLatin1Char('^')))
@@ -194,6 +200,7 @@ void RegExprRule::doReplaceExpressions(const QStringList &captures)
 
 void RegExprRule::doProgressFinished()
 {
+    m_progress = nullptr;
     m_isCached = false;
 }
 
@@ -234,6 +241,7 @@ bool RegExprRule::doMatchSucceed(const QString &text,
         return true;
 
     m_isCached = true;
+    m_progress = progress;
     progress->trackRule(this);
 
     return false;
diff --git a/src/plugins/texteditor/generichighlighter/specificrules.h b/src/plugins/texteditor/generichighlighter/specificrules.h
index 051ab81d26..63beaf8df9 100644
--- a/src/plugins/texteditor/generichighlighter/specificrules.h
+++ b/src/plugins/texteditor/generichighlighter/specificrules.h
@@ -114,7 +114,7 @@ private:
 class RegExprRule : public DynamicRule
 {
 public:
-    virtual ~RegExprRule() {}
+    virtual ~RegExprRule();
 
     void setPattern(const QString &pattern);
     void setInsensitive(const QString &insensitive);
@@ -136,6 +136,7 @@ private:
     int m_length = 0;
     QStringList m_captures;
     QRegExp m_expression;
+    ProgressData *m_progress = nullptr;
 };
 
 class KeywordRule : public Rule