Globaly replace all new operators

Question

I'm using an RTOS in an (embedded) C++ application. Since i'm working on an embedded target i try to keep the heap allocations to a minimum. However at some point STL classes like vector come in very handy.

Because i'm using a RTOS, i have to make sure that the new/malloc() call is thread safe. Luckyly my RTOS (FreeRTOS) provides it's own (threadsafe) malloc() routines. I only do have to use them.

So far i implemented the following new/delete pair and linked it into the binary.

void * operator new(size_t n) noexcept(false);


void operator delete(void * p) noexcept(true);


void operator delete(void * p, size_t n) noexcept(true);

However looking at this

https://en.cppreference.com/w/cpp/memory/new/operator_new

shows me a dozen overloads of new (and as many overloads for delete). Do all new or delete overloads default to my replacement or am i missing an operator overload?

Answer 1

The default behaviour of the standard library for many of the operator new and operator delete overloads is to forward to the "basic" versions of operator new and operator delete .

The "basic" operators are:

void* operator new (std::size_t count);
void* operator new (std::size_t count, std::align_val_t alignment); // C++17 only
void operator delete(void* ptr) noexcept;
void operator delete(void* ptr, std::align_val_t alignment) noexcept; // C++17 only

Assuming that you have a standard library implementation that implements the default behaviour as defined in the C++ standard¹, the above operators are the only ones that you need to replace.

The default behaviour was first defined in the C++11 standard, so your standard library implementation must support this at minimum.

[1]: See the section titled "Storage allocation and deallocation [new.delete]" in a C++ standard.