Warning in repeated_ptr_field.h about conversion from `size_t` to `int` causes compiler error

[grossag]

What version of protobuf and what language are you using?
Version: main/v6.30.1
Language: C++

What operating system (Linux, Windows, ...) and version?

Windows

What runtime / compiler are you using (e.g., python version or gcc version)

MSVC 17.12.5

What did you do?
I am compiling code that includes a generated .pb.h file.

What did you expect to see
What did you see instead?

I am running into compiler warnings, which are treated as errors:

C:\dev\conan-cache\p\protoee6b55d34d238\p\include\google/protobuf/repeated_ptr_field.h(1575): error C2220: the following warning is treated as an error
C:\dev\conan-cache\p\protoee6b55d34d238\p\include\google/protobuf/repeated_ptr_field.h(1575): warning C4267: 'argument': conversion from 'size_t' to 'int', possible loss of data
C:\dev\conan-cache\p\protoee6b55d34d238\p\include\google/protobuf/repeated_ptr_field.h(1580): warning C4267: 'argument': conversion from 'size_t' to 'int', possible loss of data
C:\dev\conan-cache\p\protoee6b55d34d238\p\include\google/protobuf/repeated_ptr_field.h(1584): warning C4267: 'argument': conversion from 'size_t' to 'int', possible loss of data
C:\dev\conan-cache\p\protoee6b55d34d238\p\include\google/protobuf/repeated_field.h(145): warning C4267: 'argument': conversion from 'size_t' to 'const _Ty', possible loss of data

I believe that this issue still exists in the codebase:

• RustRepeatedMessageHelper::Reserve adds a size_t to the result of RepeatedPtrFieldBase::size() (which is int). This results in a size_t value.
• The result of this is passed into RepeatedPtrFieldBase::Reserve which is an int.
• This results in the warning about conversion from size_t to int.

Anything else we should know about your project / environment

[anandolee]

Can you help to create a PR. We are happy to accept PRs like this