Re: Determination of argument passed to operator new

[Jonathan Wakely <jwakely dot gcc at gmail dot com>]

On 14 October 2016 at 18:26, Nikolaus Dunn wrote:
> Hi all,
>
> According to what I've read, the "new" and "new []" expressions are
> implemented by the compiler to compute the size of the storage required by
> the type and then make a call to one of the "new" operators to allocate
> memory and handle construction. I've found the code for the "new" operators
> in gcc, but I can't find where in the gcc code the compiler determines the
> value to be passed to the new operator and then sets up the actual call.

Look for build_new() in gcc/cp/init.c

> The reason I'm asking is I am interested in how the compiler implements the
> "new []" expression. In particular, how it is storing the array size and is
> there any extra overhead being stored and what it is, if any.

That is specified by the ABI, see
https://mentorembedded.github.io/cxx-abi/abi.html#array-cookies

> I'm assuming it is the actual parser/code generator that is doing this since
> they are unique expressions and not simply function calls. Can someone point
> me to where this code is being generated or correct my ignorance if I am way
> off base?