Module errors 

Error subsystem (§21, §85 Phase 1).

Implements the libxml2 error reporting infrastructure:

• xmlError struct management
• Error domain/code registry
• Structured error callbacks (thread-local storage)
• Generic error callbacks (thread-local storage)
• Last-error tracking (thread-local xmlGetLastError, xmlResetLastError, xmlCopyError)
• Error message formatting
• xmlRaiseError() — the central error reporting function

UPSTREAM-PARITY

libxml2 has a two-tier error system:

1. Structured errors — xmlStructuredErrorFunc receives an xmlErrorPtr with all structured fields (domain, code, level, line, etc.)

2. Generic errors — xmlGenericErrorFunc receives a formatted string (printf-style). This is the older system, still widely used.

Both systems coexist. When both handlers are set, both are called. The last error is stored thread-locally for retrieval via xmlGetLastError.

Phase 1 status

Complete — all error functions are implemented. Variadic message formatting will be enhanced in Phase 2+.

Functions

copy_error^⚠

Copy an error from one location to another.

format_error_message

Format an error message.

get_last_error

Get the last error for the current thread.

raise_error^⚠

Raise an error — the central error reporting function.

reset_error^⚠

Reset an error structure to its default state.

reset_last_error

Reset the last error for the current thread.

set_generic_error_func^⚠

Set the generic error handler.

set_structured_error_func^⚠

Set the structured error handler.