added comments to know where the test should break

tests-err/test14.c

@@ -1,7 +1,7 @@
 main() {
     int a;
-    typedef b = (a);
+    typedef b = (a);            // typedef ‘b’ is initialized (use __typeof__ instead)
     typeof (int *) c;
-    typeof (d[0](1)) e;
+    typeof (d[0](1)) e;         // ‘d’ undeclared (first use in this function) 
     c = &a;
-}
+}

tests-err/test15.c

@@ -1,20 +1,20 @@
     //generalized lvalues
 foo() {
       int a,b,f;
-     (a, b) += 5;
-     a, (b += 5);
-     &(a, b);
+     (a, b) += 5;               					// lvalue required as left operand of assignment            
+     a, (b += 5);					
+     &(a, b);										// lvalue required as unary ‘&’ operand
      a, &b;
-     (a ? b : c) = 5 ; 
+     (a ? b : c) = 5 ; 								// ‘c’ undeclared (first use in this function)
      (a ? b = 5 : (c = 5)) ;
 
-     (int)a = 5 ; 
+     (int)a = 5 ; 									// lvalue required as left operand of assignment
      (int)(a = (char *)(int)5) ;
 
-     (int)a += 5;
+     (int)a += 5;									// lvalue required as left operand of assignment
      (int)(a = (char *)(int) ((int)a + 5));
 
-    (int)f = 1;
+    (int)f = 1;										// lvalue required as left operand of assignment
     (int *)&f;
 }
 

tests-err/test23.c

@@ -4,9 +4,8 @@ now() {
      double y;
      void hack (union foo);
      union foo u;
-     u = (union foo) x  ==  u.i = x;
-     u = (union foo) y  ==  u.d = y;
+     u = (union foo) x  ==  u.i = x;    // invalid operands to binary == (have ‘union foo’ and ‘int’)
+     u = (union foo) y  ==  u.d = y;	// invalid operands to binary == (have ‘union foo’ and 'double')
      hack ((union foo) x);
 
-}        
-
+}    

tests-err/test26.c

@@ -1,6 +1,5 @@
      func (x, y) {
-        int x, y;
+        int x, y;          // ‘x’ redeclared as different kind of symbol / ‘y’ redeclared as different kind of symbol
         return x+y;
      }
 
-

tests-err/test41.c

@@ -8,7 +8,5 @@ switch (x) {
     break;
  case 2: y=90;
     break;
- default:
-}
-}
-
+ default:		// label at end of compound statement
+}

tests-err/test43.c

@@ -8,7 +8,7 @@ goto l66;;
 } else {
 y=100;
  y++;
-l66:
+l66:				// label at end of compound statement
 }
 
 }

tests-err/test45.c

@@ -6,7 +6,7 @@ void gg (h765t *q23w3)
 {
     if (q23w3->ll881ss[3]) {
        if (1) {
-           q23w3->ll881ss[3] = (void *) (++(int)q23w3->ll881ss[3]);
+           q23w3->ll881ss[3] = (void *) (++(int)q23w3->ll881ss[3]);		// lvalue required as increment operand
        }
     }
-}
+}

tests-err/test5.c

@@ -12,7 +12,7 @@ PyMapping_SetItemString(o, key, value)
   if( ! key) return Py_ReturnNullError(),-1;
   if (!(okey=PyString_FromString(key))) return -1;
   r = PyObject_SetItem(o,okey,value);
-  if (--( okey )->ob_refcnt != 0) ; else (*(  okey  )->ob_type->tp_dealloc)((PyObject *)(  okey  ))  ;
+  if (--( okey )->ob_refcnt != 0) ; else (*(  okey  )->ob_type->tp_dealloc)((PyObject *)(  okey  ))  ;  // (1)request for member ‘ob_refcnt’ in something not a structure or union /  (2)request for member ‘ob_type’ in something not a structure or union
+  //			^(1)								 ^(2)
   return r;
-}
-
+}

tests-err/test57.c

@@ -1,6 +1,6 @@
 
 void F(char l)
 {
-        return l<= '\~';
+        return l<= '\~';        		// ‘return’ with a value, in function returning void / unknown escape sequence: '\~'
 }
 

tests-err/test66.c

@@ -1,4 +1,3 @@
 f (__builtin_va_alist )
-     int __builtin_va_alist;...
-{ }
-
+     int __builtin_va_alist;...		// expected declaration specifiers before ‘...’ token
+{ }									// expected ‘{’ at end of input