fixed #13673 - fixed signedCharArrayIndex detection [skip ci]

Author: firewave

lib/checkother.cpp

@@ -2023,7 +2023,7 @@ void CheckOther::checkCharVariable()
                 if (!tok->variable()->isArray() && !tok->variable()->isPointer())
                     continue;
                 const Token *index = tok->next()->astOperand2();
-                if (warning && tok->variable()->isArray() && astIsSignedChar(index) && index->getValueGE(0x80, *mSettings))
+                if (warning && tok->variable()->isArray() && astIsSignedChar(index) && index->getValueLE(-1, *mSettings))
                     signedCharArrayIndexError(tok);
                 if (portability && astIsUnknownSignChar(index) && index->getValueGE(0x80, *mSettings))
                     unknownSignCharArrayIndexError(tok);

lib/token.cpp

@@ -1922,6 +1922,7 @@ const ValueFlow::Value * Token::getValueLE(const MathLib::bigint val, const Sett
 {
     if (!mImpl->mValues)
         return nullptr;
+    // TODO: assert the given value is actually possible - i.e. 0x80 for a signed char is not possible
     return ValueFlow::findValue(*mImpl->mValues, settings, [&](const ValueFlow::Value& v) {
         return !v.isImpossible() && v.isIntValue() && v.intvalue <= val;
     });
@@ -1931,6 +1932,7 @@ const ValueFlow::Value * Token::getValueGE(const MathLib::bigint val, const Sett
 {
     if (!mImpl->mValues)
         return nullptr;
+    // TODO: assert the given value is actually possible - i.e. 0x80 for a signed char is not possible
     return ValueFlow::findValue(*mImpl->mValues, settings, [&](const ValueFlow::Value& v) {
         return !v.isImpossible() && v.isIntValue() && v.intvalue >= val;
     });
@@ -1940,6 +1942,7 @@ const ValueFlow::Value * Token::getValueNE(MathLib::bigint val) const
 {
     if (!mImpl->mValues)
         return nullptr;
+    // TODO: assert the given value is actually possible - i.e. 0x80 for a signed char is not possible
     const auto it = std::find_if(mImpl->mValues->cbegin(), mImpl->mValues->cend(), [=](const ValueFlow::Value& value) {
         return value.isIntValue() && !value.isImpossible() && value.intvalue != val;
     });

test/testcharvar.cpp

@@ -68,6 +68,14 @@ class TestCharVar : public TestFixture {
               "}");
         ASSERT_EQUALS("[test.cpp:5:5]: (portability) 'char' type used as array index. [unknownSignCharArrayIndex]\n", errout_str());
 
+        check("int buf[256];\n"
+              "void foo()\n"
+              "{\n"
+              "    signed char ch = 0x80;\n"
+              "    buf[ch] = 0;\n"
+              "}");
+        ASSERT_EQUALS("[test.cpp:5:5]: (warning) Signed 'char' type used as array index. [signedCharArrayIndex]\n", errout_str());
+
         check("int buf[256];\n"
               "void foo()\n"
               "{\n"
@@ -92,6 +100,14 @@ class TestCharVar : public TestFixture {
               "}");
         ASSERT_EQUALS("[test.cpp:5:5]: (portability) 'char' type used as array index. [unknownSignCharArrayIndex]\n", errout_str());
 
+        check("int buf[256];\n"
+              "void foo()\n"
+              "{\n"
+              "    signed char ch = 0x80;\n"
+              "    buf[ch] = 0;\n"
+              "}");
+        ASSERT_EQUALS("[test.cpp:5:5]: (warning) Signed 'char' type used as array index. [signedCharArrayIndex]\n", errout_str());
+
         check("int buf[256];\n"
               "void foo(signed char ch)\n"
               "{\n"
@@ -113,6 +129,13 @@ class TestCharVar : public TestFixture {
               "}");
         ASSERT_EQUALS("[test.cpp:3:24]: (portability) 'char' type used as array index. [unknownSignCharArrayIndex]\n", errout_str());
 
+        check("void foo(char* buf)\n"
+              "{\n"
+              "    signed char ch = 0x80;"
+              "    buf[ch] = 0;\n"
+              "}");
+        ASSERT_EQUALS("[test.cpp:3:31]: (warning) Signed 'char' type used as array index. [signedCharArrayIndex]\n", errout_str());
+
         check("void foo(char* buf)\n"
               "{\n"
               "    char ch = 0;"