To me, the relevant justification is: This is intended to allow compiler transfor- mations, such as removal of empty loops, even when termination cannot be proven. Presumably, this is because proving termination mechanically is difficult, and the inability to prove termination hampers compilers which could otherwise make useful transformations, such as moving nondependent operations from … Read more
It’s not an operator. In all senses of the word, it’s not one. It has been a huge misconception since it was introduced and despite popular opinion — it’s not one, and there are a few objective points to be made: It doesn’t fit the definition of an operator It can’t be used as an … Read more
Yes, it’s legal. From the C99 draft standard: §6.5.2.1, paragraph 2: A postfix expression followed by an expression in square brackets [] is a subscripted designation of an element of an array object. The definition of the subscript operator [] is that E1[E2] is identical to (*((E1)+(E2))). Because of the conversion rules that apply to … Read more
Yes, the code is standard conforming. The + triggers a conversion to a plain old function pointer for the lambda. What happens is this: The compiler sees the first lambda ([]{}) and generates a closure object according to §5.1.2. As the lambda is a non-capturing lambda, the following applies: 5.1.2 Lambda expressions [expr.prim.lambda] 6 The … Read more
The evaluation order of elements in an expression is unspecified (except some very particular cases, such as the && and || operators and the ternary operator, which introduce sequence points); so, it’s not guaranteed that test will be evaluated before or after foo(test) (which modifies it). If your code relies on a particular order of … Read more
The C11 standard explicitly mentions these two: int main(void); int main(int argc, char* argv[]); although it does mention the phrase “or equivalent” with the following footnote: Thus, int can be replaced by a typedef name defined as int, or the type of argv can be written as char ** argv, and so on. In addition, … Read more
In Fortran >=90, the best approach is use intrinsic functions to specify the precision you need — this guarantees both portability and that you get the precision that you need. For example, to obtain integers i and my_int that will support at least 8 decimal digits, you could use: integer, parameter :: RegInt_K = selected_int_kind … Read more
Yes, this change was driven by changes in the language which makes it undefined behavior if an indeterminate value is produced by an evaluation but with some exceptions for unsigned narrow characters. Defect report 1787 whose proposed text can be found in N39141 was recently accepted in 2014 and is incorporated in the latest working … Read more
Your pseudo-code is pretty much correct. For this example, suppose we had a method call foo.bar() where foo: T. I’m going to use the fully qualified syntax (FQS) to be unambiguous about what type the method is being called with, e.g. A::bar(foo) or A::bar(&***foo). I’m just going to write a pile of random capital letters, … 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