Evaluate container size in program memory

lib/programmemory.cpp

@@ -34,6 +34,15 @@ bool ProgramMemory::getTokValue(nonneg int varid, const Token** result) const
     return found;
 }
 
+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;
+}
+
 void ProgramMemory::setUnknown(nonneg int varid)
 {
     values[varid].valueType = ValueFlow::Value::ValueType::UNINIT;
@@ -534,6 +543,25 @@ void execute(const Token *expr,
         else
             *error = true;
     }
+    else if (Token::Match(expr->tokAt(-3), "%var% . %name% (")) {
+        const Token* containerTok = expr->tokAt(-3);
+        if (astIsContainer(containerTok) && containerTok->varId() > 0) {
+            Library::Container::Yield yield = containerTok->valueType()->container->getYield(expr->strAt(-1));
+            if (yield == Library::Container::Yield::SIZE) {
+                if (!programMemory->getContainerSizeValue(containerTok->varId(), result))
+                    *error = true;
+            } else if (yield == Library::Container::Yield::EMPTY) {
+                MathLib::bigint size = 0;
+                if (!programMemory->getContainerSizeValue(containerTok->varId(), &size))
+                    *error = true;
+                *result = (size == 0);
+            } else {
+                *error = true;
+            }
+        } else {
+            *error = true;
+        }
+    }
 
     else
         *error = true;

lib/programmemory.h

@@ -19,6 +19,8 @@ struct ProgramMemory {
     bool getIntValue(nonneg int varid, MathLib::bigint* result) const;
     void setIntValue(nonneg int varid, MathLib::bigint value);
 
+    bool getContainerSizeValue(nonneg int varid, MathLib::bigint* result) const;
+
     void setUnknown(nonneg int varid);
 
     bool getTokValue(nonneg int varid, const Token** result) const;

lib/valueflow.cpp

@@ -5773,6 +5773,8 @@ static bool isContainerSizeChanged(const Token *tok, int depth)
         return true;
     if (Token::Match(tok, "%name% %assign%|<<"))
         return true;
+    if (Token::Match(tok, "%var% [") && tok->valueType()->container->stdAssociativeLike)
+        return true;
     if (Token::Match(tok, "%name% . %name% (")) {
         Library::Container::Action action = tok->valueType()->container->getAction(tok->strAt(2));
         Library::Container::Yield yield = tok->valueType()->container->getYield(tok->strAt(2));

test/teststl.cpp

@@ -335,6 +335,16 @@ private:
                     "    x[0] = 0;\n"
                     "}\n");
         ASSERT_EQUALS("", errout.str());
+
+        checkNormal("void f(bool b) {\n"
+                    "    std::vector<int> x;\n"
+                    "    if (b)\n"
+                    "        x.push_back(1);\n"
+                    "    if (x.size() < 2)\n"
+                    "        return;\n"
+                    "    x[0] = 2;\n"
+                    "}\n");
+        ASSERT_EQUALS("", errout.str());
     }
 
     void outOfBoundsIndexExpression() {