C++ freestanding features

Question

What are the features that I can use in c++ freestanding environment? I am developing a little kernel (for my own pleasure) and I know that I can't use the whole stdlib library, but what else ? when I tried to use the new and delete operators it compiled without troubles but the linker said

undefined reference to `operator new[](unsigned long)
undefined reference to `operator delete[](void*)'

I link with -lgcc and -lsupc++ options. I know that exception handling is disable in freestanding but I am a little bit surprised that new and delete are also. So what can I use and what can I not?

Worldling

Answer 1

What are the features that I can use in c++ freestanding environment?

Much of freestanding implementations is implementation defined:

[intro.compliance] ... A freestanding implementation is one in which execution may take place without the benefit of an operating system, and has an implementation-defined set of libraries that includes certain language-support libraries

[intro.multithread] ... Under a freestanding implementation, it is implementation-defined whether a program can have more than one thread of execution.

[basic.start.main] It is implementation-defined whether a program in a freestanding environment is required to define a main function. [ Note: In a freestanding environment, start-up and termination is implementation-defined; start- up contains the execution of constructors for objects of namespace scope with static storage duration; termination contains the execution of destructors for objects with static storage duration. — end note ]

[using.headers] C ++ headers for freestanding implementations

<ciso646>
<cstddef>
<cfloat>
<limits>
<climits>
<cstdint>
<cstdlib>
<new>
<typeinfo>
<exception>
<initializer_list>
<cstdalign>
<cstdarg>
<cstdbool>
<atomic>

[compliance] The supplied version of the header <cstdlib> shall declare at least the functions abort, atexit, at_quick_- exit, exit, and quick_exit (18.5). The other headers listed in this table shall meet the same requirements as for a hosted implementation.

Note that malloc/free are not listed in the required functions of <cstdlib>.

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As far as your linker error is concerned, neither freestanding, nor hosted implementation is required to provide those overloads:

[replacement.functions] A C ++ program may provide the definition for any of twelve dynamic memory allocation function signatures declared in header <new>

In practice, since a free standing environment cannot depend on an OS, and malloc is usually implemented using features provided by an OS, it is unlikely to have free store memory management features in a freestanding environment. Conversely, a hosted environment requires free store memory management to implement the features of the standard library.

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