C is pass by value. The value assigned to table is lost on returning from InitStringTable(). Also when allocating pointers to char ask for room for pointers to char. So this: … = (char**)malloc(sizeof(char)*10); shall at least be (assuming C): … = malloc(sizeof(char*)*10); A possible approach to this would be: #include <stdlib.h> #include <string.h> #include … Read more
TL:DR: intptr_t might be best in some cases because the signed-overflow boundary is in the middle of the “non-canonical hole”. Treating a value as negative instead of huge may be better if wrapping from zero to 0xFF…FF or vice versa is possible, but pointer+size for any valid size can’t wrap a value from INT64_MAX to … Read more
This should work: let address = sqlite3_column_text(statement, 0) let string = String.fromCString(UnsafePointer<CChar>(address)) Update for Swift 3 (Xcode 8), compare Swift 3: convert a null-terminated UnsafePointer<UInt8> to a string: let string = String(cString: sqlite3_column_text(statement, 0)) Update: sqlite3_column_text() returns an implicitly unwrapped optional, and that is why you can pass it to String(cString:) directly. But according to … Read more
To understand what’s going on here, two language rules are important: Arrays are not assignable. An array can be converted to a pointer to its first element. It’s also important to understand what a string literal like “Sunstroke” is. It’s a static array of constant characters, large enough to hold all the characters of a … Read more
Yep you are missing out on a lot 🙂 To avoid another wall of text I’ll link to an answer I wrote earlier today explaining multi-dimensional arrays. With that in mind, arr is a 1-D array with 4 elements, each of which is an array of 5 ints. When used in an expression other than … Read more
The answer is copy semantics. When you pass an object by value in C++, e.g. printArea(Shape shape) a copy is made of the object you pass. And if you pass a derived class to this function, all that’s copied is the base class Shape. If you think about it, there’s no way the compiler could … Read more
Listing [SciPy.Docs]: C-Types Foreign Function Interface (numpy.ctypeslib) (and [Python.Docs]: ctypes – A foreign function library for Python just in case). This is a exactly like [SO]: C function called from Python via ctypes returns incorrect value (@CristiFati’s answer) (a duplicate), it just happens to also involve NumPy. In other words, you have Undefined Behavior, as … Read more
Why Infinite loop? Infinite loop is because of self loop in your list after calling swap() function. In swap() code following statement is buggy. (*b)->next = (temp1)->next; Why?: Because after the assignment statement in swap() function temp1‘s next starts pointing to b node. And node[b]‘s next point to itself in a loop. And the self … Read more
You can’t treat arrays polymorphically, so while new B[100] creates an array of B objects and returns a pointer to the array – or equivalently the first element of the array – and while it is valid to assign this pointer to a pointer to a base class, it is not valid to treat this … Read more
Note that pointer subtraction and pointer comparison are different operations with different rules. C++14 5.6/6, on subtracting pointers: Unless both pointers point to elements of the same array object or one past the last element of the array object, the behavior is undefined. C++14 5.9/3-4: Comparing pointers to objects is defined as follows: If two … Read more