Fix #12117 FP integerOverflowCond for shift by 31 bits (cppcheck-opensource#5596)

chrchr-github · web-flow · commit cae27c5ec770 · 2023-10-28T16:47:57.000+02:00
diff --git a/lib/checktype.cpp b/lib/checktype.cpp
@@ -205,8 +205,8 @@ void CheckType::checkIntegerOverflow()
             continue;
 
         // For left shift, it's common practice to shift into the sign bit
-        //if (tok->str() == "<<" && value->intvalue > 0 && value->intvalue < (((MathLib::bigint)1) << bits))
-        //    continue;
+        if (tok->str() == "<<" && value->intvalue > 0 && value->intvalue < (((MathLib::bigint)1) << bits))
+            continue;
 
         integerOverflowError(tok, *value);
     }
diff --git a/test/testtype.cpp b/test/testtype.cpp
@@ -295,6 +295,11 @@ class TestType : public TestFixture {
               "   return 123456U * x;\n"
               "}",settings);
         ASSERT_EQUALS("", errout.str());
+
+        check("int f(int i) {\n" // #12117
+              "    return (i == 31) ? 1 << i : 0;\n"
+              "}", settings);
+        ASSERT_EQUALS("[test.cpp:2] -> [test.cpp:2]: (warning) Shifting signed 32-bit value by 31 bits is undefined behaviour. See condition at line 2.\n", errout.str());
     }
 
     void signConversion() {

Original file line number	Diff line number	Diff line change
`@@ -205,8 +205,8 @@ void CheckType::checkIntegerOverflow()`
`205`	`205`	`continue;`
`206`	`206`
`207`	`207`	`// For left shift, it's common practice to shift into the sign bit`
`208`		`- //if (tok->str() == "<<" && value->intvalue > 0 && value->intvalue < (((MathLib::bigint)1) << bits))`
`209`		`- // continue;`
	`208`	`+ if (tok->str() == "<<" && value->intvalue > 0 && value->intvalue < (((MathLib::bigint)1) << bits))`
	`209`	`+ continue;`
`210`	`210`
`211`	`211`	`integerOverflowError(tok, *value);`
`212`	`212`	`}`