fix #13995: performance regression (hang) in 2.18dev (danmar#7653)

Author: ludviggunne

lib/valueflow.cpp

@@ -541,6 +541,8 @@ size_t ValueFlow::getSizeOf(const ValueType &vt, const Settings &settings, Accur
             const size_t charBit = settings.platform.char_bit;
             size_t n = ValueFlow::getSizeOf(vt2, settings,accuracy, ++maxRecursion);
             size_t a = getAlignOf(vt2, settings, accuracy);
+            if (n == 0 || a == 0)
+                return accuracy == Accuracy::ExactOrZero ? 0 : total;
             if (bits == 0) {
                 if (currentBitfieldAlloc == 0) {
                     bits = n * charBit;
@@ -565,8 +567,6 @@ size_t ValueFlow::getSizeOf(const ValueType &vt, const Settings &settings, Accur
                 currentBitCount += bits;
                 return ret;
             }
-            if (n == 0 || a == 0)
-                return accuracy == Accuracy::ExactOrZero ? 0 : total;
             n *= dim;
             size_t padding = (a - (total % a)) % a;
             if (currentBitCount > 0) {

test/testvalueflow.cpp

@@ -176,6 +176,8 @@ class TestValueFlow : public TestFixture {
 
         TEST_CASE(performanceIfCount);
         TEST_CASE(bitfields);
+
+        TEST_CASE(bitfieldsHang);
     }
 
     static bool isNotTokValue(const ValueFlow::Value &val) {
@@ -9136,6 +9138,12 @@ class TestValueFlow : public TestFixture {
         testBitfields("unsigned char a : 16;\n",
                       2);
     }
+
+    void bitfieldsHang() {
+        const char *code = "struct S { unknown_type x : 1; };\n"
+                           "const size_t size = sizeof(S);\n";
+        (void)valueOfTok(code, "x");
+    }
 };
 
 REGISTER_TEST(TestValueFlow)