ProParser: Guard against OOM

When the pattern for a regular expression is empty, every character
of the source is replaced with a copy of the "after" part of a
"QString::replace(re, after)". If input and output are huge this results
in a bad_alloc. We catch that here.

Fixes: QTCREATORBUG-16957
Change-Id: If512f407a2170d93ae7e4182219d9926945b14de
Reviewed-by: Christian Kandeler <christian.kandeler@qt.io>

src/shared/proparser/qmakeevaluator.cpp

@@ -877,10 +877,16 @@ QMakeEvaluator::VisitReturn QMakeEvaluator::visitProVariable(
         QRegularExpression regexp(pattern, case_sense ? QRegularExpression::NoPatternOption :
                                                         QRegularExpression::CaseInsensitiveOption);
 
+        try
+        {
             // We could make a union of modified and unmodified values,
             // but this will break just as much as it fixes, so leave it as is.
             replaceInList(&valuesRef(varName), regexp, replace, global, m_tmp2);
             debugMsg(2, "replaced %s with %s", dbgQStr(pattern), dbgQStr(replace));
+        } catch (const std::bad_alloc &e) {
+            qWarning() << "Bad alloc caught in replaceInList:" << e.what();
+            return ReturnError;
+        }
     } else {
         ProStringList varVal;
         if (expandVariableReferences(tokPtr, sizeHint, &varVal, false) == ReturnError)