ftp: use int for sent to preserve SSL_write()

[zeff-ir]

What is fixed

SSL_write() returns int and uses negative values to indicate errors.
The variable sent in ext/ftp/ftp.c was declared as size_t, which
caused negative return values to be converted into large positive numbers.

Why it matters

Although this value is later passed to SSL_get_error(), the OpenSSL API
requires the original return value of SSL_write() to be used. Passing a
converted unsigned value may lead to incorrect error handling and potentially
report a failed write as a success.

Why change is safe

While the implicit int → size_t → int conversion is “usually” safe on most
compilers, it relies on implementation-defined behavior. Using a signed int
makes the code clearer, avoids subtle portability issues, and directly matches
the return type contract of SSL_write().

How it is fixed

Changed the type of sent from size_t to int.

[TimWolla]

Could probably be SSL_write_ex instead, which has a size_t out parameter.

[zeff-ir]

I chose this approach for easier backporting to PHP 8.3 (which supports OpenSSL ≥ 1.0.2 and is my primary focus). Since SSL_write_ex is only available from 1.1.1.

Could probably be SSL_write_ex instead, which has a size_t out parameter.

I can rework the PR if you prefer that variant for master.

[iluuu1994]

LGTM, thanks!

[nielsdos]

This is also wrong as my_send_wrapper_with_restart returns an ssize_t.
Edit: nvm reading on mobile is hard. The max size that can be sent shouldn't actually be a size_t in the first place, as that can truncate...

[zeff-ir]

This is also wrong as my_send_wrapper_with_restart returns an ssize_t.
Edit: nvm reading on mobile is hard. The max size that can be sent shouldn't actually be a size_t in the first place, as that can truncate...

Thanks for the review. I’ve pushed a new version.

[bukka]

OpenSSL 1.1.1 is minimum since 8.4 so you can use SSL_write_ex if you target 8.4+ which should be fine for this. Not sure if we should even treat it as a bug but I'm fine either way.