Fix issue 10194: hang with followAllReferences() (#3189)

* Decrease depth faster when there is multiple returns

Author: pfultz2

lib/astutils.cpp

@@ -806,11 +806,11 @@ std::vector<ReferenceToken> followAllReferences(const Token* tok, bool inconclus
             if (!Function::returnsReference(f))
                 return {{tok, std::move(errors)}};
             std::set<ReferenceToken, ReferenceTokenLess> result;
-            for (const Token* returnTok : Function::findReturns(f)) {
+            std::vector<const Token*> returns = Function::findReturns(f);
+            for (const Token* returnTok : returns) {
                 if (returnTok == tok)
                     continue;
-                std::vector<ReferenceToken> argvarRt = followAllReferences(returnTok, inconclusive, errors, depth - 1);
-                for (const ReferenceToken& rt:followAllReferences(returnTok, inconclusive, errors, depth - 1)) {
+                for (const ReferenceToken& rt:followAllReferences(returnTok, inconclusive, errors, depth - returns.size())) {
                     const Variable* argvar = rt.token->variable();
                     if (!argvar)
                         return {{tok, std::move(errors)}};
@@ -825,7 +825,7 @@ std::vector<ReferenceToken> followAllReferences(const Token* tok, bool inconclus
                         ErrorPath er = errors;
                         er.emplace_back(returnTok, "Return reference.");
                         er.emplace_back(tok->previous(), "Called function passing '" + argTok->expressionString() + "'.");
-                        std::vector<ReferenceToken> refs = followAllReferences(argTok, inconclusive, std::move(er), depth - 1);
+                        std::vector<ReferenceToken> refs = followAllReferences(argTok, inconclusive, std::move(er), depth - returns.size());
                         result.insert(refs.begin(), refs.end());
                         if (!inconclusive && result.size() > 1)
                             return {{tok, std::move(errors)}};

lib/valueflow.cpp

@@ -2663,7 +2663,7 @@ std::vector<LifetimeToken> getLifetimeTokens(const Token* tok, bool escape, Valu
             for (const Token* returnTok : returns) {
                 if (returnTok == tok)
                     continue;
-                for (LifetimeToken& lt : getLifetimeTokens(returnTok, escape, errorPath, depth - 1)) {
+                for (LifetimeToken& lt : getLifetimeTokens(returnTok, escape, errorPath, depth - returns.size())) {
                     const Token* argvarTok = lt.token;
                     const Variable* argvar = argvarTok->variable();
                     if (!argvar)
@@ -2680,7 +2680,7 @@ std::vector<LifetimeToken> getLifetimeTokens(const Token* tok, bool escape, Valu
                         lt.errorPath.emplace_back(returnTok, "Return reference.");
                         lt.errorPath.emplace_back(tok->previous(), "Called function passing '" + argTok->expressionString() + "'.");
                         std::vector<LifetimeToken> arglts = LifetimeToken::setInconclusive(
-                                                                getLifetimeTokens(argTok, escape, std::move(lt.errorPath), depth - 1), returns.size() > 1);
+                                                                getLifetimeTokens(argTok, escape, std::move(lt.errorPath), depth - returns.size()), returns.size() > 1);
                         result.insert(result.end(), arglts.begin(), arglts.end());
                     }
                 }

test/testvalueflow.cpp

@@ -5447,6 +5447,47 @@ class TestValueFlow : public TestFixture {
                "       &b}}}};\n"
                "}\n";
         valueOfTok(code, "x");
+
+        code = "int &a(int &);\n"
+               "int &b(int &);\n"
+               "int &c(int &);\n"
+               "int &d(int &e) {\n"
+               "  if (!e)\n"
+               "    return a(e);\n"
+               "  if (e > 0)\n"
+               "    return b(e);\n"
+               "  if (e < 0)\n"
+               "    return c(e);\n"
+               "  return e;\n"
+               "}\n"
+               "int &a(int &e) { \n"
+               "  if (!e)\n"
+               "    return d(e); \n"
+               "  if (e > 0)\n"
+               "    return b(e);\n"
+               "  if (e < 0)\n"
+               "    return c(e);\n"
+               "  return e;\n"
+               "}\n"
+               "int &b(int &e) { \n"
+               "  if (!e)\n"
+               "    return a(e); \n"
+               "  if (e > 0)\n"
+               "    return c(e);\n"
+               "  if (e < 0)\n"
+               "    return d(e);\n"
+               "  return e;\n"
+               "}\n"
+               "int &c(int &e) { \n"
+               "  if (!e)\n"
+               "    return a(e); \n"
+               "  if (e > 0)\n"
+               "    return b(e);\n"
+               "  if (e < 0)\n"
+               "    return d(e);\n"
+               "  return e;\n"
+               "}\n";
+        valueOfTok(code, "x");
     }
 
     void valueFlowCrashConstructorInitialization() { // #9577