Module debug 

Debug/memory debugging infrastructure (§85 Phase 7).

UPSTREAM-PARITY: Corresponds to debugXML.c / debugXML.h in libxml2.

The libxml2 debug APIs for printing tree structure, XPath expressions, etc. These are used by xmllint --debug and other diagnostic tools.

Upstream contract

Mirrors upstream debugXML.c / debugXML.h (SRC-LIBXML2-2.15.0-DEBUGXML-C, parity target libxml2 2.15.3 oracle): xmlDebugDumpNode, xmlDebugDumpNodeList, xmlDebugDumpOneNode, xmlDebugDumpAttrList, xmlDebugDumpString and the xmllint --debug tree dump format.

Conceptual behavior

Implements the recursive debug dumper: nodes are printed with type, name, content, attributes, namespaces, line numbers and children at increasing indentation (MAX_DEPTH guard), plus the XPath expression and string dumps used by xmllint diagnostics.

Ownership & safety invariants

The dump functions borrow the tree — they never free or detach nodes; output goes to the caller-provided FILE* (or a buffer) that the caller owns. Namespace strings are read via their href (bounded scans), never stored.

Historical quirks & epochs

The dump format is one of the most stable surfaces: the debug-simple / debug-dtd / debug-nodes / debug-ns matrix cases are byte-identical across the whole 2.7.8 → 2.15.3 span (SEMANTIC_EPOCHS.md stable cases). One deliberate epoch join: entity content children dump as TEXT compact since 2.13.0 (E-004, commit 8d04f0ee 2024-03-11, R-000119) — the candidate matches the 2.13+ epoch, i.e. the current oracle.

Deliberate oddities

The TEXT compact marker is reproduced exactly (including the 14/15-byte compact threshold that is unchanged in every tested version), rather than normalized to plain TEXT.

Proving courts

The xmllint –debug CLI differential courts and the debug-* matrix cases compare dumps byte-identical against each built oracle (2.7.8 through 2.15.3); cargo test covers the unit dump suites.

Tempting simplifications that would break parity

Do not normalize the dump format (e.g. always printing TEXT or collapsing attributes): xmllint –debug output is a byte-exact parity target and downstream tooling parses it. Do not drop the compact-text threshold logic — R-000119/E-004 depend on it.

Functions

xmlBoolToText^⚠

Convert a boolean to text.

xmlDebugDumpAttr^⚠

Dump a debug representation of an attribute.

xmlDebugDumpAttrList^⚠

Dump a debug representation of an attribute list.

xmlDebugDumpDocument^⚠

Dump an entire document.

xmlDebugDumpDocumentHead^⚠

Dump the document head (first few nodes).

xmlDebugDumpNode^⚠

Dump a node and its subtree.

xmlDebugDumpNodeList^⚠

Dump a node list.

xmlDebugDumpOneNode^⚠

Dump a single node for debug output.

xmlDebugDumpString^⚠

Dump a debug representation of an xmlChar string.

xmlLsCountNode^⚠

Count the number of nodes in a list reachable via next pointers.

xmlLsOneNode^⚠

Dump a single node summary (like ls -l for nodes).

Type Aliases

_IO_FILE

Re-export _IO_FILE type for C ABI compatibility.