From d7de46f50e66f3b9607462dc1d563fd31f767313 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Daniel=20Marjam=C3=A4ki?= <daniel.marjamaki@gmail.com>
Date: Sat, 8 Sep 2018 10:43:08 +0200
Subject: [PATCH] ValueFlow: Fix false positive for container size

---
 lib/valueflow.cpp      | 12 +++++++-----
 test/testvalueflow.cpp |  7 +++++++
 2 files changed, 14 insertions(+), 5 deletions(-)

diff --git a/lib/valueflow.cpp b/lib/valueflow.cpp
index 97c1a9b2b..571990cd4 100644
--- a/lib/valueflow.cpp
+++ b/lib/valueflow.cpp
@@ -3495,7 +3495,7 @@ static void valueFlowContainerReverse(const Token *tok, unsigned int containerId
     }
 }
 
-static void valueFlowContainerForward(const Token *tok, unsigned int containerId, const ValueFlow::Value &value, const Settings *settings)
+static void valueFlowContainerForward(const Token *tok, unsigned int containerId, const ValueFlow::Value &value, const Settings *settings, bool cpp)
 {
     while (nullptr != (tok = tok->next())) {
         if (Token::Match(tok, "[{}]"))
@@ -3504,6 +3504,8 @@ static void valueFlowContainerForward(const Token *tok, unsigned int containerId
             continue;
         if (Token::Match(tok, "%name% ="))
             break;
+        if (isLikelyStreamRead(cpp, tok->astParent()))
+            break;
         if (isContainerSizeChangedByFunction(tok))
             break;
         if (!tok->valueType() || !tok->valueType()->container)
@@ -3566,7 +3568,7 @@ static void valueFlowContainerSize(TokenList *tokenlist, SymbolDatabase* symbold
         }
         value.valueType = ValueFlow::Value::ValueType::CONTAINER_SIZE;
         value.setKnown();
-        valueFlowContainerForward(var->nameToken()->next(), var->declarationId(), value, settings);
+        valueFlowContainerForward(var->nameToken()->next(), var->declarationId(), value, settings, tokenlist->isCPP());
     }
 
     // after assignment
@@ -3578,7 +3580,7 @@ static void valueFlowContainerSize(TokenList *tokenlist, SymbolDatabase* symbold
                     ValueFlow::Value value(Token::getStrLength(containerTok->tokAt(2)));
                     value.valueType = ValueFlow::Value::ValueType::CONTAINER_SIZE;
                     value.setKnown();
-                    valueFlowContainerForward(containerTok->next(), containerTok->varId(), value, settings);
+                    valueFlowContainerForward(containerTok->next(), containerTok->varId(), value, settings, tokenlist->isCPP());
                 }
             }
         }
@@ -3627,7 +3629,7 @@ static void valueFlowContainerSize(TokenList *tokenlist, SymbolDatabase* symbold
                 if (Token::simpleMatch(after, "} else {"))
                     after = isEscapeScope(after->tokAt(2), tokenlist) ? nullptr : after->linkAt(2);
                 if (after && !isContainerSizeChanged(tok->varId(), scope.bodyStart, after))
-                    valueFlowContainerForward(after, tok->varId(), value, settings);
+                    valueFlowContainerForward(after, tok->varId(), value, settings, tokenlist->isCPP());
             }
 
             // known value in conditional code
@@ -3637,7 +3639,7 @@ static void valueFlowContainerSize(TokenList *tokenlist, SymbolDatabase* symbold
                     parent = parent->astParent();
                 if (!parent) {
                     value.setKnown();
-                    valueFlowContainerForward(scope.bodyStart, tok->varId(), value, settings);
+                    valueFlowContainerForward(scope.bodyStart, tok->varId(), value, settings, tokenlist->isCPP());
                 }
             }
         }
diff --git a/test/testvalueflow.cpp b/test/testvalueflow.cpp
index cbc04a29b..991878015 100644
--- a/test/testvalueflow.cpp
+++ b/test/testvalueflow.cpp
@@ -3371,6 +3371,13 @@ private:
                "}";
         ASSERT_EQUALS("", isKnownContainerSizeValue(tokenValues(code, "ints . front"), 10));
 
+        code = "void f() {\n"
+               "  std::string s;\n"
+               "  cin >> s;\n"
+               "  s[0];\n"
+               "}";
+        ASSERT(tokenValues(code, "s [").empty());
+
         code = "void f() {\n"
                "  std::string s=\"abc\";\n" // size of s is 3
                "  s.size();\n"