FIx issue 9895: ValueFlow: Wrong known value below function call with reference parameter

lib/programmemory.cpp

@@ -5,19 +5,30 @@
 #include "symboldatabase.h"
 #include <algorithm>
 #include <cassert>
+#include <memory>
 
 void ProgramMemory::setValue(nonneg int varid, const ValueFlow::Value &value)
 {
     values[varid] = value;
 }
+const ValueFlow::Value* ProgramMemory::getValue(nonneg int varid) const
+{
+    const ProgramMemory::Map::const_iterator it = values.find(varid);
+    const bool found = it != values.end() && !it->second.isImpossible();
+    if (found)
+        return &it->second;
+    else
+        return nullptr;
+}
 
 bool ProgramMemory::getIntValue(nonneg int varid, MathLib::bigint* result) const
 {
-    const ProgramMemory::Map::const_iterator it = values.find(varid);
-    const bool found = it != values.end() && it->second.isIntValue();
-    if (found)
-        *result = it->second.intvalue;
-    return found;
+    const ValueFlow::Value* value = getValue(varid);
+    if (value && value->isIntValue()) {
+        *result = value->intvalue;
+        return true;
+    }
+    return false;
 }
 
 void ProgramMemory::setIntValue(nonneg int varid, MathLib::bigint value)
@@ -27,20 +38,22 @@ void ProgramMemory::setIntValue(nonneg int varid, MathLib::bigint value)
 
 bool ProgramMemory::getTokValue(nonneg int varid, const Token** result) const
 {
-    const ProgramMemory::Map::const_iterator it = values.find(varid);
-    const bool found = it != values.end() && it->second.isTokValue();
-    if (found)
-        *result = it->second.tokvalue;
-    return found;
+    const ValueFlow::Value* value = getValue(varid);
+    if (value && value->isTokValue()) {
+        *result = value->tokvalue;
+        return true;
+    }
+    return false;
 }
 
 bool ProgramMemory::getContainerSizeValue(nonneg int varid, MathLib::bigint* result) const
 {
-    const ProgramMemory::Map::const_iterator it = values.find(varid);
-    const bool found = it != values.end() && it->second.isContainerSizeValue();
-    if (found)
-        *result = it->second.intvalue;
-    return found;
+    const ValueFlow::Value* value = getValue(varid);
+    if (value && value->isContainerSizeValue()) {
+        *result = value->intvalue;
+        return true;
+    }
+    return false;
 }
 
 void ProgramMemory::setUnknown(nonneg int varid)

lib/programmemory.h

@@ -15,6 +15,7 @@ struct ProgramMemory {
     Map values;
 
     void setValue(nonneg int varid, const ValueFlow::Value &value);
+    const ValueFlow::Value* getValue(nonneg int varid) const;
 
     bool getIntValue(nonneg int varid, MathLib::bigint* result) const;
     void setIntValue(nonneg int varid, MathLib::bigint value);

test/testvalueflow.cpp

@@ -164,6 +164,24 @@ private:
         return false;
     }
 
+    bool testValueOfXImpossible(const char code[], unsigned int linenr, int value) {
+        // Tokenize..
+        Tokenizer tokenizer(&settings, this);
+        std::istringstream istr(code);
+        tokenizer.tokenize(istr, "test.cpp");
+
+        for (const Token *tok = tokenizer.tokens(); tok; tok = tok->next()) {
+            if (tok->str() == "x" && tok->linenr() == linenr) {
+                for (const ValueFlow::Value& val:tok->values()) {
+                    if (val.isImpossible() && val.intvalue == value)
+                        return true;
+                }
+            }
+        }
+
+        return false;
+    }
+
     bool testValueOfX(const char code[], unsigned int linenr, int value) {
         // Tokenize..
         Tokenizer tokenizer(&settings, this);
@@ -2449,6 +2467,17 @@ private:
                "    return x;\n"
                "}\n";
         ASSERT_EQUALS(true, testValueOfX(code, 9U, 0));
+
+        code = "void g(long& a);\n"
+               "void f(long a) {\n"
+               "    if (a == 0)\n"
+               "        return;\n"
+               "    if (a > 1)\n"
+               "         g(a);\n"
+               "    int x = a;\n"
+               "    return x;\n"
+               "}\n";
+        ASSERT_EQUALS(false, testValueOfXImpossible(code, 8U, 0));
     }
 
     void valueFlowAfterConditionExpr() {