40 lines
1.9 KiB
Markdown
40 lines
1.9 KiB
Markdown
# Execution traces
|
||
|
||
Browser ECMAScript APIs expose compilation, match, capture and replacement
|
||
results, but no V8, SpiderMonkey or JavaScriptCore execution trace. Regex Tools
|
||
does not relabel structural explanations, static findings or timing
|
||
observations as an ECMAScript engine trace.
|
||
|
||
PCRE2 10.47 has a separate actual automatic-callout vertical. ABI version 3
|
||
compiles the requested pattern with `PCRE2_AUTO_CALLOUT`, registers an
|
||
application callback, and copies only:
|
||
|
||
- callout number;
|
||
- pattern byte position and next-item byte length;
|
||
- subject byte position;
|
||
- capture-top and capture-last numbers;
|
||
- bounded current mark text.
|
||
|
||
These fields have `reported` provenance. Pattern and subject byte boundaries
|
||
are validated and normalized to exact editor UTF-16 positions while the native
|
||
values remain visible.
|
||
|
||
Collection runs in `pcre2-trace.worker`, not the normal execution worker. It
|
||
uses the selected PCRE2 match, depth and heap limits plus the supervisor wall
|
||
clock. The callback retains only complete 32-byte records and mark slices under
|
||
both a 50,000-event and 10 MiB serialized-data hard cap. At a cap it returns
|
||
PCRE2’s reserved `PCRE2_ERROR_CALLOUT`, abandoning the native match; the result
|
||
retains that native status, the last complete event and an explicit truncation
|
||
flag. Timeout, cancellation or crash discards the complete worker.
|
||
|
||
The viewer derives “forward”, “same position” and “apparent backtrack” solely
|
||
from the difference between adjacent reported subject positions. Each label
|
||
has `derived` provenance. This is useful navigation, not a claim that the
|
||
stream reports every internal action. PCRE2 start optimizations can also
|
||
conclude some requests without any callout.
|
||
|
||
Tracing represents one exact `pcre2_match()` invocation. The application-level
|
||
`g` iteration flag is not applied, and that fact is reported. Normal match,
|
||
replacement, tests, corpus, comparisons and benchmarks never use the
|
||
instrumented trace path.
|