When replacing an owned constant by a different type (constant or
shared) replace with the correct type instead of defaulting to
shared.

https://github.com/ruby/prism/commit/fbe9b131a1

Share the empty source string in `pm_string_mapped_init` and
`pm_string_file_init`.

https://github.com/ruby/prism/commit/f7a9a03a92

https://github.com/ruby/prism/commit/d1d2161219

https://github.com/ruby/prism/commit/d2d9a1f1a7

[Bug #21161]

The `tolower` function provided by the libc is locale dependent
and can behave in ways you wouldn't expect for some value
of `LC_CTYPE`.

https://github.com/ruby/prism/commit/e3488256b4

Co-Authored-By: Nobuyoshi Nakada <nobu@ruby-lang.org>

According to the calloc(3) man page, when nmemb or size is 0, `calloc()` can either return NULL or a unique pointer that can be passed to `free()`.
While gcc and clang typically return a unique pointer, mruby's `mrb_calloc()` returns NULL in this case.

Since `pm_constant_pool_init()` is commonly called with capacity=0 during normal operation of Prism, explicitly handle this case by setting `list->ids` to NULL when capacity is 0.
This approach is portable across different calloc implementations and avoids potential issues with mruby's allocation behavior.

This maintains compatibility with `free()` and `realloc()`, as passing NULL pointers to these functions is explicitly allowed by their specifications.

https://github.com/ruby/prism/commit/1c32252df7

https://github.com/ruby/prism/commit/b4b7a69ce7

When mmap fails for any reason, the fd must be closed.

Coverity Scan found this issue.

https://github.com/ruby/prism/commit/c06e9c400f

It looks like we can possibly do an out of bounds read if size is equal
to 0.  This commit adds a conditional to ensure size is actually greater
than 0 before looking backwards in the buffer

https://github.com/ruby/prism/commit/2031b626e6