Partial fix for #13529 FN: zerodiv (#7191)

Author: chrchr-github

lib/vf_settokenvalue.cpp

@@ -479,7 +479,7 @@ namespace ValueFlow
                 if (!isComputableValue(parent, value1))
                     continue;
                 for (const Value &value2 : parent->astOperand2()->values()) {
-                    if (value1.path != value2.path)
+                    if (value1.path != value2.path && value1.path != 0 && value2.path != 0)
                         continue;
                     if (!isComputableValue(parent, value2))
                         continue;

test/testother.cpp

@@ -59,6 +59,7 @@ class TestOther : public TestFixture {
         TEST_CASE(zeroDiv18);
         TEST_CASE(zeroDiv19);
         TEST_CASE(zeroDiv20); // #11175
+        TEST_CASE(zeroDiv21);
 
         TEST_CASE(zeroDivCond); // division by zero / useless condition
 
@@ -679,6 +680,17 @@ class TestOther : public TestFixture {
         ASSERT_EQUALS("[test.cpp:4]: (error) Division by zero.\n", errout_str());
     }
 
+    void zeroDiv21()
+    {
+        check("int f(int n) {\n"
+              "    return 1 / ((1 / n) - 1);\n"
+              "}\n"
+              "int g() {\n"
+              "    return f(1);\n"
+              "}\n");
+        ASSERT_EQUALS("[test.cpp:2]: (error) Division by zero.\n", errout_str());
+    }
+
     void zeroDivCond() {
         check("void f(unsigned int x) {\n"
               "  int y = 17 / x;\n"