Improve valeflow analysis with comparison operators (#1131)

* Improve valeflow analysis with comparison operators

* Use simple match

* Dont add 0 on comparisons

* Check reverse comparisons

* Use nullptr

* Remove duplicate code tests

lib/valueflow.cpp

@@ -2354,7 +2354,10 @@ static void valueFlowAfterCondition(TokenList *tokenlist, SymbolDatabase* symbol
         const Scope * scope = symboldatabase->functionScopes[i];
         std::set<unsigned> aliased;
         for (Token* tok = const_cast<Token*>(scope->classStart); tok != scope->classEnd; tok = tok->next()) {
-            const Token *vartok, *numtok;
+            const Token * vartok = nullptr;
+            const Token * numtok = nullptr;
+            const Token * lowertok = nullptr;
+            const Token * uppertok = nullptr;
 
             if (Token::Match(tok, "= & %var% ;"))
                 aliased.insert(tok->tokAt(2)->varId());
@@ -2372,7 +2375,35 @@ static void valueFlowAfterCondition(TokenList *tokenlist, SymbolDatabase* symbol
                 }
                 if (vartok->str() == "=" && vartok->astOperand1() && vartok->astOperand2())
                     vartok = vartok->astOperand1();
-                if (!vartok->isName() || !numtok->hasKnownIntValue())
+                if (!vartok->isName())
+                    continue;
+            } else if (Token::simpleMatch(tok, ">")) {
+                if (!tok->astOperand1() || !tok->astOperand2())
+                    continue;
+                if (tok->astOperand1()->hasKnownIntValue()) {
+                    uppertok = tok->astOperand1();
+                    vartok = tok->astOperand2();
+                } else {
+                    lowertok = tok->astOperand2();
+                    vartok = tok->astOperand1();
+                }
+                if (vartok->str() == "=" && vartok->astOperand1() && vartok->astOperand2())
+                    vartok = vartok->astOperand1();
+                if (!vartok->isName())
+                    continue;
+            } else if (Token::simpleMatch(tok, "<")) {
+                if (!tok->astOperand1() || !tok->astOperand2())
+                    continue;
+                if (tok->astOperand1()->hasKnownIntValue()) {
+                    lowertok = tok->astOperand1();
+                    vartok = tok->astOperand2();
+                } else {
+                    uppertok = tok->astOperand2();
+                    vartok = tok->astOperand1();
+                }
+                if (vartok->str() == "=" && vartok->astOperand1() && vartok->astOperand2())
+                    vartok = vartok->astOperand1();
+                if (!vartok->isName())
                     continue;
             } else if (tok->str() == "!") {
                 vartok = tok->astOperand1();
@@ -2390,6 +2421,13 @@ static void valueFlowAfterCondition(TokenList *tokenlist, SymbolDatabase* symbol
                 continue;
             }
 
+            if(numtok && !numtok->hasKnownIntValue())
+                continue;
+            if(lowertok && !lowertok->hasKnownIntValue())
+                continue;
+            if(uppertok && !uppertok->hasKnownIntValue())
+                continue;
+
             const unsigned int varid = vartok->varId();
             if (varid == 0U)
                 continue;
@@ -2402,7 +2440,21 @@ static void valueFlowAfterCondition(TokenList *tokenlist, SymbolDatabase* symbol
                 continue;
             }
             std::list<ValueFlow::Value> values;
-            values.push_back(ValueFlow::Value(tok, numtok ? numtok->values().front().intvalue : 0LL));
+            // TODO: We should add all known values
+            if(numtok) {
+                values.push_back(ValueFlow::Value(tok, numtok->values().front().intvalue));
+            } else if(lowertok) {
+                long long v = lowertok->values().front().intvalue;
+                values.push_back(ValueFlow::Value(tok, v+1));
+
+            } else if(uppertok) {
+                long long v = uppertok->values().front().intvalue;
+                values.push_back(ValueFlow::Value(tok, v-1));
+
+            } else {
+                values.push_back(ValueFlow::Value(tok, 0LL));
+
+            }
 
             if (Token::Match(tok->astParent(), "%oror%|&&")) {
                 Token *parent = const_cast<Token*>(tok->astParent());
@@ -2453,7 +2505,7 @@ static void valueFlowAfterCondition(TokenList *tokenlist, SymbolDatabase* symbol
 
                 // based on the comparison, should we check the if or while?
                 int codeblock = 0;
-                if (Token::Match(tok, "==|>=|<=|!"))
+                if (Token::Match(tok, "==|>=|<=|!|>|<"))
                     codeblock = 1;
                 else if (Token::Match(tok, "%name%|!="))
                     codeblock = 2;

test/testvalueflow.cpp

@@ -1732,6 +1732,40 @@ private:
                "}";
         ASSERT_EQUALS(false, testValueOfX(code, 3U, 123));
 
+        code = "void f(int x) {\n"
+               "    if (x > 123) {\n"
+               "        a = x;\n"
+               "    }\n"
+               "}";
+        ASSERT_EQUALS(true, testValueOfX(code, 3U, 124));
+        ASSERT_EQUALS(false, testValueOfX(code, 3U, 123));
+
+        code = "void f(int x) {\n"
+               "    if (x < 123) {\n"
+               "        a = x;\n"
+               "    }\n"
+               "}";
+        ASSERT_EQUALS(true, testValueOfX(code, 3U, 122));
+        ASSERT_EQUALS(false, testValueOfX(code, 3U, 123));
+
+        // ----
+
+        code = "void f(int x) {\n"
+               "    if (123 < x) {\n"
+               "        a = x;\n"
+               "    }\n"
+               "}";
+        ASSERT_EQUALS(true, testValueOfX(code, 3U, 124));
+        ASSERT_EQUALS(false, testValueOfX(code, 3U, 123));
+
+        code = "void f(int x) {\n"
+               "    if (123 > x) {\n"
+               "        a = x;\n"
+               "    }\n"
+               "}";
+        ASSERT_EQUALS(true, testValueOfX(code, 3U, 122));
+        ASSERT_EQUALS(false, testValueOfX(code, 3U, 123));
+
         // in else
         code = "void f(int x) {\n"
                "    if (x == 123) {}\n"