Reviewing the basic terminology It’s usually good enough – unless you’re programming assembly – to envisage a pointer containing a numeric memory address, with 1 referring to the second byte in the process’s memory, 2 the third, 3 the fourth and so on…. What happened to 0 and the first byte? Well, we’ll get to … Read more
This is CWG 232. That issue might seem like it’s mainly about dereferencing a null pointer but it’s fundamentally about what it means to simply dereference something that doesn’t point to an object. There is no explicit language rule about this case. One of the examples in the issue is: Similarly, dereferencing a pointer to … Read more
Array dereferencing became available in PHP 5.4 That’s why this doesn’t work in PHP 5.3. So you have an extra step where you need to get the array value from your function call and then you can use it: $variable = $this->greatestId(); if ($variable[“num_rows”] > 0){ // do stuff }
Line 11 is p1 = &a; where p1 has type int ** and a has type int[3], right? Well; &a has type int(*)[3] and that type is not compatible with int** as the compiler told you You may want to try p1 = &p0; And read the c-faq, particularly section 6. In short: arrays are … Read more
Thanks to the link provided by @tesseract in the comments: Expert C Programming: Deep C Secrets (page 96), I came up with a simple answer (a simple dumb down version of the explanation in the book; for a full academic answer read the book): when declared int a[2]: the compiler has for a an address … Read more
I saw a question the other day where someone inadvertently used an incomplete type by specifying something like struct a { int q; }; struct A *x; x->q = 3; The compiler knew that struct A was a struct, despite A being totally undefined, by virtue of the struct keyword. That was in C++, where … Read more
This is a known issue regarding how the function traits are inferred through Deref. As a workaround, you need to explicitly get a mutable reference by doing a mutable reborrow: let mut t = Foo; (&mut *t)(); or by calling DerefMut::deref_mut: let mut t = Foo; t.deref_mut()();
I think the second opus of What every C programmer should know about Undefined Behavior might help illustrate this issue. Taking the example of the blog: void contains_null_check(int *P) { int dead = *P; if (P == 0) return; *P = 4; } Might be optimized to (RNCE: Redundant Null Check Elimintation): void contains_null_check_after_RNCE(int *P) … Read more
1) Pointers are not arrays. Arrays are not pointers. Don’t think of them that way because they are different. How can I prove this? Think about what they look like in memory: Our array arr is 10 characters long. It contains “Hello”, but wait, that’s not all! Because we have a statically declared array longer … Read more
The standard correctly defines the return type of an assignment operator. Actually, the assignment operation itself doesn’t depend on the return value – that’s why the return type isn’t straightforward to understanding. The return type is important for chaining operations. Consider the following construction: a = b = c;. This should be equal to a … Read more