Fix #13076 FP uninitvar with unknown struct definition (danmar#7158)

Author: chrchr-github

lib/valueflow.cpp

@@ -2785,6 +2785,8 @@ static bool isDecayedPointer(const Token *tok)
         return false;
     if (!tok->astParent())
         return false;
+    if (Token::simpleMatch(tok->astParent(), "=") && astIsRHS(tok))
+        return true;
     if (astIsPointer(tok->astParent()) && !Token::simpleMatch(tok->astParent(), "return"))
         return true;
     if (tok->astParent()->isConstOp())

test/testvalueflow.cpp

@@ -743,6 +743,17 @@ class TestValueFlow : public TestFixture {
             lifetimes = lifetimeValues(code, "return"); // don't crash
             ASSERT_EQUALS(true, lifetimes.empty());
         }
+
+        {
+            const char code[] = "void f() {\n" // #13076
+                                "    char a[10];\n"
+                                "    struct S s = { sizeof(a), 0 };\n"
+                                "    s.p = a;\n"
+                                "}\n";
+            lifetimes = lifetimeValues(code, "= a");
+            ASSERT_EQUALS(true, lifetimes.size() == 1);
+            ASSERT_EQUALS(true, lifetimes.front() == "a");
+        }
     }
 
     void valueFlowArrayElement() {