Let’s consider this example code: #include <stddef.h> int *f(void) { return NULL; } int g(int x) { return x == NULL ? 3 : 4; } We want f to compile without warnings, and we want g to cause an error or a warning (because an int variable x was compared to a pointer). In … Read more
Stephan T. Lavavej (member of the C++ standard committee) explained that once in a talk (55:35): While an implementation is allowed to #define NULL nullptr, it would break quite some uses like int i = NULL; and apparently there are plenty of those. So they could not force the change.
I have a draft version of the C standard (ISO/IEC 9899:1999), and it has some fun things to say about that call. For starters, it mentions (ยง7.21.1/2) in regards to memcpy that Where an argument declared as size_t n specifies the length of the array for a function, n can have the value zero on … Read more
Yes, there is some compiler magic that optimises Option<ptr> to a single pointer (most of the time). use std::mem::size_of; macro_rules! show_size { (header) => ( println!(“{:<22} {:>4} {}”, “Type”, “T”, “Option<T>”); ); ($t:ty) => ( println!(“{:<22} {:4} {:4}”, stringify!($t), size_of::<$t>(), size_of::<Option<$t>>()) ) } fn main() { show_size!(header); show_size!(i32); show_size!(&i32); show_size!(Box<i32>); show_size!(&[i32]); show_size!(Vec<i32>); show_size!(Result<(), Box<i32>>); } … Read more
Both (a) and (b) result in undefined behavior. It’s always undefined behavior to call a member function through a null pointer. If the function is static, it’s technically undefined as well, but there’s some dispute. The first thing to understand is why it’s undefined behavior to dereference a null pointer. In C++03, there’s actually a … Read more
You need to include a jar that this class exists in. You can find it here If using Maven, you can add the following dependency declaration: <dependency> <groupId>com.google.code.findbugs</groupId> <artifactId>jsr305</artifactId> <version>3.0.2</version> </dependency> and for Gradle: dependencies { testImplementation ‘com.google.code.findbugs:jsr305:3.0.2’ }
You can; the null pointer is implicitly converted into boolean false while non-null pointers are converted into true. From the C++11 standard, section on Boolean Conversions: A prvalue of arithmetic, unscoped enumeration, pointer, or pointer to member type can be converted to a prvalue of type bool. A zero value, null pointer value, or null … Read more
delete performs the check anyway, so checking it on your side adds overhead and looks uglier. A very good practice is setting the pointer to NULL after delete (helps avoiding double deletion and other similar memory corruption problems). I’d also love if delete by default was setting the parameter to NULL like in #define my_delete(x) … Read more