The stack and heap in C/C++ describe different mechanisms of memory allocation. They can also be called “automatic storage” and “free store”. If you allocate data on the free store/heap, you are responsible for managing the lifetime (calling
free()). This is mostly unrelated to memory pages.
Memory pages are a block of virtual addresses. The virtual address space of a process is created by the operating system by mapping pages into the address space.
A process uses different areas of the address space differently. One area will be the stack. Other areas will hold the contents of executable files and libraries. These files may have different segments, e.g. for executable code, for constants, and space for variables.
Here I've pulled the address space mappings of a Perl interpreter using pmap:
0000000000400000 1776K r-x-- perl
00000000007bb000 4K r---- perl
00000000007bc000 12K rw--- perl
00000000007bf000 4K rw--- [ anon ]
0000000001eff000 1192K rw--- [ anon ]
00007f00184b7000 4464K r---- locale-archive
00007f0018913000 1792K r-x-- libc-2.23.so
00007f0018ad3000 2048K ----- libc-2.23.so
00007f0018cd3000 16K r---- libc-2.23.so
00007f0018cd7000 8K rw--- libc-2.23.so
00007f0018cd9000 16K rw--- [ anon ]
00007f0018cdd000 36K r-x-- libcrypt-2.23.so
00007f0018ce6000 2044K ----- libcrypt-2.23.so
00007f0018ee5000 4K r---- libcrypt-2.23.so
00007f0018ee6000 4K rw--- libcrypt-2.23.so
00007f0018ee7000 184K rw--- [ anon ]
00007f0018f15000 1056K r-x-- libm-2.23.so
00007f001901d000 2044K ----- libm-2.23.so
00007f001921c000 4K r---- libm-2.23.so
00007f001921d000 4K rw--- libm-2.23.so
00007f001921e000 12K r-x-- libdl-2.23.so
00007f0019221000 2044K ----- libdl-2.23.so
00007f0019420000 4K r---- libdl-2.23.so
00007f0019421000 4K rw--- libdl-2.23.so
00007f0019422000 96K r-x-- libpthread-2.23.so
00007f001943a000 2044K ----- libpthread-2.23.so
00007f0019639000 4K r---- libpthread-2.23.so
00007f001963a000 4K rw--- libpthread-2.23.so
00007f001963b000 16K rw--- [ anon ]
00007f001963f000 152K r-x-- ld-2.23.so
00007f0019839000 20K rw--- [ anon ]
00007f0019864000 4K r---- ld-2.23.so
00007f0019865000 4K rw--- ld-2.23.so
00007f0019866000 4K rw--- [ anon ]
00007ffc0cd0a000 136K rw--- [ stack ]
00007ffc0cd4e000 12K r---- [ anon ]
00007ffc0cd51000 8K r-x-- [ anon ]
ffffffffff600000 4K r-x-- [ anon ]
Note that the smallest size is 4K, that is the page size on my system.
We can see on the rightmost column which files (executables or libraries) were mapped into the address space at which offset. There are also a couple of special regions, such as
[stack]. Some of the anonymous regions can be used as a free store/heap. There may be gaps between the mapped ranges of the address space. Trying to access memory in an unmapped range will cause a segfault.
Each of those regions consists of one or more pages. This is important, because pages can have access protections: the executables and libraries provide executable pages for code, read-only pages for constants, and read-write pages for variables. This is a security mechanism to avoid arbitrary data from being executed (though this doesn't matter very much for an interpreter). The pages for the heap and stack will be readable and writeable, but not executable.
An address range may be mapped, but the page for that address might not exist at the moment. Using such an address will trigger a page fault. The operating system can intercept the page fault and add the page. For example, not all pages of the 136K for the stack may exist when the process starts. Instead, the pages are added on demand. Or, a page may have been swapped out to disk. A page fault will cause that page to be loaded back into physical memory.