Function pio_build_info 

#[unsafe(no_mangle)]
pub extern "C" fn pio_build_info() -> *mut c_char

Everything a loader needs to decide what this library can do, as one owned JSON document. Free the returned string with pio_string_free. Infallible.

curl_version_info is the shape: one call, one report, and new keys arrive without a new symbol. Keys are only added. A caller with no JSON parser keeps using pio_has_feature and pio_abi_version, which say the same things one answer at a time.

error_categories lists the tokens that prefix an errbuf message. The ABI reports errors as text, so a consumer that wants to branch on the kind of failure matches these rather than parsing prose. They are stable; a new category may be added.