Sigil 0.4.0

January 14, 2026release

This release makes Sigil leaner and faster. Native list operations cut compilation time in half, release binaries are 44% smaller, and a new profiling module helps you find bottlenecks in your own code. Macro authors get full hygiene support, and error handling improves with catchable VM errors and cleaner stack traces.

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Breaking Changes

sigil-web: Renamed UI components from sigil-* to sg-* prefix (e.g., sigil-button becomes sg-button) to mirror data-sg-* attributes

Performance

Profiling revealed hotspots in list operations during macro expansion. Native C implementations of assoc, assq, assv, member, memq, and memv deliver significant speedups:

Test suite runs 2x faster (33s → 15s)
Module compilation 50% faster
Release binaries 44% smaller (3.2MB → 1.8MB)

Macro Hygiene

Full hygienic macro support for syntax-rules and syntax-case. Macros now properly respect lexical scope, preventing accidental variable capture:

Local and module-level hygiene
free-identifier=? for comparing identifiers during expansion
#' reader shorthand for (syntax ...) expressions
New (sigil syntax) module with syntax->datum, datum->syntax, generate-temporaries

Error Handling

Catchable VM errors: guard can now catch type errors, division by zero, and out-of-bounds access. Use the new vm-error? predicate in (sigil error).
Better stack traces: Errors display file paths with line and column positions. Anonymous lambda frames are filtered by default for cleaner output.

Profiling

New (sigil profile) module for performance analysis:

(with-profiling
  (my-expensive-operation))
(profile-report)  ; Shows call counts, timing, allocations

Library Improvements

sigil-http: Keyword arguments for make-http-server and http-serve (port:, host:, handler:)
sigil-sxml: New sxml->html for converting SXML trees to HTML strings
sigil-version: New package for semantic version parsing and comparison

Bug Fixes

Fixed source file names in error stack traces
Fixed socket API consistency across platforms
Fixed with-api-docs path resolution in sigil-publish
Fixed sigil-irc package dependency declaration