Include known value in unreachable switch case error message

Author: JeewoongKim

lib/checkother.cpp

@@ -1015,16 +1015,16 @@ void CheckOtherImpl::checkUnreachableSwitchCase()
                 continue;
             if (switchValue->intvalue == caseValue->intvalue)
                 continue;
-            unreachableSwitchCaseError(tok, caseExpression->expressionString());
+            unreachableSwitchCaseError(tok, caseExpression->expressionString(), MathLib::toString(switchValue->intvalue));
         }
     }
 }
 
-void CheckOtherImpl::unreachableSwitchCaseError(const Token* tok, const std::string& caseExpression)
+void CheckOtherImpl::unreachableSwitchCaseError(const Token* tok, const std::string& caseExpression, const std::string& switchValue)
 {
     reportError(tok, Severity::style, "unreachableSwitchCase",
                 "Switch case '" + caseExpression +
-                "' can never be selected because the switch condition has a known value.",
+                "' can never be selected because the switch condition is known to be " + switchValue + ".",
                 CWE561, Certainty::normal);
 }
 
@@ -4968,7 +4968,7 @@ void CheckOther::getErrorMessages(ErrorLogger& errorLogger, const Settings &sett
     c.duplicateExpressionTernaryError(nullptr, ErrorPath{});
     c.duplicateBreakError(nullptr,  false);
     c.unreachableCodeError(nullptr, nullptr,  false);
-    c.unreachableSwitchCaseError(nullptr, "case");
+    c.unreachableSwitchCaseError(nullptr, "case", "0");
     c.unsignedLessThanZeroError(nullptr, nullptr, "varname");
     c.unsignedPositiveError(nullptr, nullptr, "varname");
     c.pointerLessThanZeroError(nullptr, nullptr);

lib/checkother.h

@@ -293,7 +293,7 @@ class CPPCHECKLIB CheckOtherImpl : public CheckImpl {
     void redundantCopyError(const Token *tok1, const Token* tok2, const std::string& var);
     void redundantBitwiseOperationInSwitchError(const Token *tok, const std::string &varname);
     void suspiciousCaseInSwitchError(const Token* tok, const std::string& operatorString);
-    void unreachableSwitchCaseError(const Token* tok, const std::string& caseExpression);
+    void unreachableSwitchCaseError(const Token* tok, const std::string& caseExpression, const std::string& switchValue);
     void selfAssignmentError(const Token *tok, const std::string &varname);
     void misusedScopeObjectError(const Token *tok, const std::string &varname, bool isAssignment = false);
     void duplicateBranchError(const Token *tok1, const Token *tok2, ErrorPath errors);

releasenotes.txt

@@ -8,6 +8,7 @@ New checks:
 - Warn when feof() is used as a while loop condition (wrongfeofUsage).
 - ftell() result is unspecified when file is opened in mode "t".
 - Detect when an STL algorithm such as std::copy, std::equal, std::transform, etc. accesses more elements through an iterator than are available in the container (algorithmOutOfBounds).
+- Detect switch cases that cannot be selected when the switch condition has a known value (unreachableSwitchCase).
 
 C/C++ support:
 -

test/testother.cpp

@@ -6361,7 +6361,7 @@ class TestOther : public TestFixture {
               "        }\n"
               "    }\n"
               "}\n");
-        ASSERT_EQUALS("[test.cpp:7:9]: (style) Switch case 'B' can never be selected because the switch condition has a known value. [unreachableSwitchCase]\n", errout_str());
+        ASSERT_EQUALS("[test.cpp:7:9]: (style) Switch case 'B' can never be selected because the switch condition is known to be 0. [unreachableSwitchCase]\n", errout_str());
 
         check("void f(int t) {\n"
               "    if (t == 0) {\n"
@@ -6373,7 +6373,7 @@ class TestOther : public TestFixture {
               "        }\n"
               "    }\n"
               "}\n");
-        ASSERT_EQUALS("[test.cpp:6:9]: (style) Switch case '1' can never be selected because the switch condition has a known value. [unreachableSwitchCase]\n", errout_str());
+        ASSERT_EQUALS("[test.cpp:6:9]: (style) Switch case '1' can never be selected because the switch condition is known to be 0. [unreachableSwitchCase]\n", errout_str());
 
         check("void f(int t) {\n"
               "    switch (t) {\n"
@@ -6401,7 +6401,7 @@ class TestOther : public TestFixture {
               "        }\n"
               "    }\n"
               "}\n");
-        ASSERT_EQUALS("[test.cpp:12:9]: (style) Switch case '1' can never be selected because the switch condition has a known value. [unreachableSwitchCase]\n", errout_str());
+        ASSERT_EQUALS("[test.cpp:12:9]: (style) Switch case '1' can never be selected because the switch condition is known to be 0. [unreachableSwitchCase]\n", errout_str());
     }
 
     void redundantContinue() {