Why is part of my code not executed? - c++

Question

I'm using Visual C++ to compile my plug-in for Cinema 4D.
GeDebugOut("-->");
subroot = NULL;
head = NULL;
tail = NULL;
success = PolygonizeHierarchy(source, hh, head, tail, &subroot, malloc);
if (!success) {
/* .. */
}
String str("not set.");
if (subroot) {
GeDebugOut("yes");
str = "yes!";
GeDebugOut("Subroot name: " + subroot->GetName());
}
else {
GeDebugOut("no");
str = "no!";
}
GeDebugOut("Is there a subroot? " + str);
GeDebugOut("<--");
The expected output is the following:
-->
yes
Subroot name: Cube
Is there a subroot? yes
<--
(or the same with "no" instead.) But I get
-->
yes
<--
Why are two prints missing here?
This is the declaration of GeDebugOut.
void GeDebugOut(const CHAR* s, ...);
void GeDebugOut(const String& s);
The String class is concatenateable. It overloads the + operator.
String(void);
String(const String& cs);
String(const UWORD* s);
String(const CHAR* cstr, STRINGENCODING type = STRINGENCODING_XBIT);
String(LONG count, UWORD fillch);
friend const String operator +(const String& Str1, const String& Str2);
const String& operator +=(const String& Str);

Answer 1

You need to use GeDebugOut like you use printf:
GeDebugOut("Some message = %s ", whatever);
where whatever is a c-string, i.e its type is char*.
Since an overload of GeDebugOut accepts String type also, then I think you need to use unicode as:
GeDebugOut(L"Is there a subroot? " + str);
// ^ note this!
because my suspicion is that if unicode is enabled, then CHAR is basically wchar_t, not char. And because of this, the string concatenation doesn't work, as the string-literal doesn't implicitly get converted into String type, to be passed to + overload.

Answer 2

You cannot append a string to a string literal.
"Is there a subroot" is a string literal and the compiler will see the use of it as a pointer to that literal.
A better way would be to do:
GeDebugOut("Is there a subroot? %s ", str);

Answer 3

As you mentioned, there are two versions of GeDebugOut the compiler can choose from:
void GeDebugOut(const CHAR* s, ...);
void GeDebugOut(const String& s);
when it encounters:
GeDebugOut("Is there a subroot? " + str);
"Is there a subroot" is a string literal, which translates to type const char*. I suspect String has a conversion operator to some numeric type. So the compiler is choosing the first overload.
This is resulting in behavior you're not expecting, because the + operation for const char* is pointer arithmetic, not string concatenation, so you're calling GeDebugOut on the pointer sum of your string literal, and whatever the output of that const char* conversion of str is.
There's several ways you can correct this. As another mentioned, you can change it to printf-like syntax. Or you can force it to use the String overlaod like so:
GeDebugOut(String("Is there a subroot?") + str);