C brace elision + nested/anonymous-member aggregate initializers

• Type: bug (cfront init lowering — hardest slice). Track C. Slice of [[bug-c-init-designated-and-nested]].
• Found: 2026-07-06 c-testsuite; scoped during that ticket's triage.

Cases

• 00050 anonymous union inside a braced init {1, 2, 3, {4, 5}} (exit 3)
• 00091 S a[1] = {{1, {2, 3}}}; nested braces array-of-struct-with-subarray
• 00205 brace-ELIDED flat init of PT cases[] (J-interpreter snippet): a fully flat list filling nested struct/array fields — currently wrong values AND wrong element count (315 output lines vs 72; sizeof(cases) wrong)

Symptom

C99 6.7.8p20 brace elision: a flat {a, b, c, d} fills nested subaggregates left-to-right, and inner {...} braces bound how many elements a subaggregate consumes. pxx's init walkers are one-level (fldI/ei flat), so nested/elided lists mis-distribute values and mis-count top-level elements → wrong [] size.

Needed (the real work)

A recursive initializer walker over the target type tree that consumes tokens with proper brace-elision semantics (open brace = descend + bound; close = pop; flat run = keep filling the current leaf sequence). Likely a rework of the init loops rather than a patch. Do AFTER [[bug-c-init-struct-designators]] + [[bug-c-init-array-designators]] land, since it subsumes their cursors.

Gate

00050/00091/00205 exit 0 + correct sizeof; drop from test/c-conformance/pxx.skip; regression tests; make test + self-host.

Log

• 2026-07-08 — resolved, commit e0f9f5e4.