Are libc and malloc part of the operating system?

Question

I was having a discussion with a co-worker about malloc, and Was wondering if it is the cases that certain libc calls like malloc are implemented by the operating system?

I always thought that malloc was calling some symbols exposed in "sys" to declare which memory addresses it would use. From what I thought the operating system would allow the program's segmentation to be specified using some os level api... which might similar to:

int assign_memory_segmention(size_t start, size_t end);

I know my stdlib.h header is part of GNU because of the GPL header... and as GNU have made sure to inform me... they are not Unix. So is malloc just some type of function pointer to an OS heap implementation?

Answer 1

This question is best asked with another question: what is an Operating System? Or if you prefer: where do you print the line between OS and standard libraries?

Technically, malloc is part of the standard C library. And since the Linux is mainly written in C, and that the same library also includes many system calls, not in the C language, it is reasonable to think that this library is part of the OS.

But, on the other hand, there are several implementations of the C library, and also, the GNU C library is available for others operating systems, such as Windows. And I'm sure that there are other languages out there that call the OS without using the standard C library. So, from that POV, it is not part of the OS.

But then, Linux is the kernel, the OS should be named GNU/Linux (citation needed). But again, there are Linux systems without GNU, such as Android...

The conclusion is: the term "Operating System" is not a technical one. If you want to be precise, use kernel or standard C library, etc.

Answer 2

Yes... and no. C malloc() is usually a sub-allocator to memory areas provided by OS calls. The OS manages all virtual memory - that is part of it's job.