Fix #10870 FN constStatement with arrays (#3904)

Makefile

@@ -407,7 +407,7 @@ validateRules:
 $(libcppdir)/analyzerinfo.o: lib/analyzerinfo.cpp externals/tinyxml2/tinyxml2.h lib/analyzerinfo.h lib/color.h lib/config.h lib/errorlogger.h lib/errortypes.h lib/importproject.h lib/path.h lib/platform.h lib/suppressions.h lib/utils.h
 	$(CXX) ${INCLUDE_FOR_LIB} $(CPPFLAGS) $(CPPFILESDIR) $(CXXFLAGS) $(UNDEF_STRICT_ANSI) -c -o $(libcppdir)/analyzerinfo.o $(libcppdir)/analyzerinfo.cpp
 
-$(libcppdir)/astutils.o: lib/astutils.cpp lib/astutils.h lib/config.h lib/errortypes.h lib/importproject.h lib/infer.h lib/library.h lib/mathlib.h lib/platform.h lib/settings.h lib/standards.h lib/suppressions.h lib/symboldatabase.h lib/templatesimplifier.h lib/timer.h lib/token.h lib/utils.h lib/valueflow.h lib/valueptr.h
+$(libcppdir)/astutils.o: lib/astutils.cpp lib/astutils.h lib/check.h lib/checkclass.h lib/config.h lib/errortypes.h lib/importproject.h lib/infer.h lib/library.h lib/mathlib.h lib/platform.h lib/settings.h lib/standards.h lib/suppressions.h lib/symboldatabase.h lib/templatesimplifier.h lib/timer.h lib/token.h lib/tokenize.h lib/tokenlist.h lib/utils.h lib/valueflow.h lib/valueptr.h
 	$(CXX) ${INCLUDE_FOR_LIB} $(CPPFLAGS) $(CPPFILESDIR) $(CXXFLAGS) $(UNDEF_STRICT_ANSI) -c -o $(libcppdir)/astutils.o $(libcppdir)/astutils.cpp
 
 $(libcppdir)/bughuntingchecks.o: lib/bughuntingchecks.cpp lib/astutils.h lib/bughuntingchecks.h lib/color.h lib/config.h lib/errorlogger.h lib/errortypes.h lib/exprengine.h lib/importproject.h lib/library.h lib/mathlib.h lib/platform.h lib/settings.h lib/standards.h lib/suppressions.h lib/symboldatabase.h lib/templatesimplifier.h lib/timer.h lib/token.h lib/utils.h lib/valueflow.h

lib/astutils.cpp

@@ -31,6 +31,7 @@
 #include "utils.h"
 #include "valueflow.h"
 #include "valueptr.h"
+#include "checkclass.h"
 
 #include <algorithm>
 #include <functional>
@@ -1747,7 +1748,7 @@ bool isConstExpression(const Token *tok, const Library& library, bool pure, bool
     return isConstExpression(tok->astOperand1(), library, pure, cpp) && isConstExpression(tok->astOperand2(), library, pure, cpp);
 }
 
-bool isWithoutSideEffects(bool cpp, const Token* tok)
+bool isWithoutSideEffects(bool cpp, const Token* tok, bool checkArrayAccess)
 {
     if (!cpp)
         return true;
@@ -1756,7 +1757,7 @@ bool isWithoutSideEffects(bool cpp, const Token* tok)
         tok = tok->astOperand2();
     if (tok && tok->varId()) {
         const Variable* var = tok->variable();
-        return var && (!var->isClass() || var->isPointer() || var->isStlType());
+        return var && (!var->isClass() || var->isPointer() || (checkArrayAccess ? var->isStlType() && !var->isStlType(CheckClass::stl_containers_not_const) : var->isStlType()));
     }
     return true;
 }

lib/astutils.h

@@ -227,7 +227,7 @@ bool isConstFunctionCall(const Token* ftok, const Library& library);
 
 bool isConstExpression(const Token *tok, const Library& library, bool pure, bool cpp);
 
-bool isWithoutSideEffects(bool cpp, const Token* tok);
+bool isWithoutSideEffects(bool cpp, const Token* tok, bool checkArrayAccess = false);
 
 bool isUniqueExpression(const Token* tok);
 

lib/checkother.cpp

@@ -1769,6 +1769,11 @@ static bool isConstStatement(const Token *tok, bool cpp)
         return tok->astParent() ? isConstStatement(tok->astOperand1(), cpp) && isConstStatement(tok->astOperand2(), cpp) : isConstStatement(tok->astOperand2(), cpp);
     if (Token::simpleMatch(tok, "?") && Token::simpleMatch(tok->astOperand2(), ":")) // ternary operator
         return isConstStatement(tok->astOperand1(), cpp) && isConstStatement(tok->astOperand2()->astOperand1(), cpp) && isConstStatement(tok->astOperand2()->astOperand2(), cpp);
+    if (Token::simpleMatch(tok, "[") && !Token::Match(tok->tokAt(-2), "%type% %name%") && isWithoutSideEffects(cpp, tok->astOperand1(), /*checkArrayAccess*/ true)) {
+        if (Token::simpleMatch(tok->astParent(), "["))
+            return isConstStatement(tok->astOperand2(), cpp) && isConstStatement(tok->astParent(), cpp);
+        return isConstStatement(tok->astOperand2(), cpp);
+    }
     return false;
 }
 
@@ -1801,6 +1806,13 @@ static bool isConstTop(const Token *tok)
         else
             return tok->astParent()->astOperand1() == tok;
     }
+    if (Token::simpleMatch(tok, "[")) {
+        const Token* bracTok = tok;
+        while (Token::simpleMatch(bracTok->astParent(), "["))
+            bracTok = bracTok->astParent();
+        if (!bracTok->astParent())
+            return true;
+    }
     return false;
 }
 
@@ -1894,6 +1906,8 @@ void CheckOther::constStatementError(const Token *tok, const std::string &type,
         msg = "Redundant code: Found unused result of ternary operator.";
     else if (tok->str() == "." && tok->tokType() == Token::Type::eOther)
         msg = "Redundant code: Found unused member access.";
+    else if (tok->str() == "[" && tok->tokType() == Token::Type::eExtendedOp)
+        msg = "Redundant code: Found unused array access.";
     else {
         reportError(tok, Severity::debug, "debug", "constStatementError not handled.");
         return;

test/testincompletestatement.cpp

@@ -498,6 +498,42 @@ private:
                       "[test.cpp:15]: (warning) Redundant code: Found unused member access.\n",
                       errout.str());
 
+        check("struct S { int a[2]{}; };\n"
+              "struct T { S s; };\n"
+              "void f() {\n"
+              "    int i[2];\n"
+              "    i[0] = 0;\n"
+              "    i[0];\n" // <--
+              "    S s[1];\n"
+              "    s[0].a[1];\n" // <--
+              "    T t;\n"
+              "    t.s.a[1];\n" // <--
+              "    int j[2][2][1] = {};\n"
+              "    j[0][0][0];\n" // <--
+              "}\n");
+        ASSERT_EQUALS("[test.cpp:6]: (warning) Redundant code: Found unused array access.\n"
+                      "[test.cpp:8]: (warning) Redundant code: Found unused array access.\n"
+                      "[test.cpp:10]: (warning) Redundant code: Found unused array access.\n"
+                      "[test.cpp:12]: (warning) Redundant code: Found unused array access.\n",
+                      errout.str());
+
+        check("void g() {\n"
+              "    int j[2]{};\n"
+              "    int k[2] = {};\n"
+              "    int l[]{ 1, 2 };\n"
+              "    int m[] = { 1, 2 };\n"
+              "    h(0, j[0], 1);\n"
+              "    C c{ 0, j[0], 1 };\n"
+              "    c[0];\n"
+              "    int j[2][2][2] = {};\n"
+              "    j[h()][0][0];\n"
+              "    j[0][h()][0];\n"
+              "    j[0][0][h()];\n"
+              "    std::map<std::string, int> M;\n"
+              "    M[\"abc\"];\n"
+              "}\n");
+        ASSERT_EQUALS("", errout.str());
+
         check("struct S { void* p; };\n" // #10875
               "void f(S s) {\n"
               "    delete (int*)s.p;\n"