C99 designated initializers + compound literals unsupported

• Type: feature (C99 parser gap)
• Track: C — cfront (compiler/cparser.inc, initializer-list parsing)
• Status: backlog
• Opened: 2026-07-02
• Found while: Track B probing untested C-frontend surface for feature-demo-chess/general C coverage.

Problem

Three related C99 initializer forms all fail to parse with expected C expression:

1. Designated struct-field initializers:

struct Point { int x, y, z; };
struct Point p = { .y = 5, .x = 1, .z = 9 };   /* order-independent, by name */

2. Designated array-index initializers:

int arr[5] = { [2] = 7, [4] = 9 };             /* sparse, by index */

3. Compound literals:

int total = sum((struct Point){ 3, 4 });       /* anonymous struct value */
int *p = (int[]){ 1, 2, 3 };                   /* anonymous array value */

All three are ordinary, reasonably common C99 constructs (designated initializers especially so — they're idiomatic for sparse tables, opt-in struct fields, and self-documenting initialization order). None currently parse; each is a separate expected C expression error at the .field = / [idx] = / (Type){...} token.

Scope

Plain brace-list initializers ({ 1, 2, 3 }, nested { {1,2}, {3,4} }) and static/global initializer lists already work elsewhere in the test suite — this ticket is specifically the three designator/compound-literal forms above.

Acceptance

• The two designated-initializer repros above compile and print the correct values (1 5 9 and 0 0 7 0 9).
• The compound-literal repros compile and print the correct values (7 and 2).
• Existing plain-brace-list C init tests stay green.

Log

• 2026-07-02 — Filed by Track B. All three forms isolated via minimal repros; no code touched — test/repro only.

• 2026-07-09 (A+B+C) — Designated initializers (both forms) DONE. Designated STRUCT-field init {.y=5,.x=1,.z=9} already worked (local record init routes through the recursive brace-elision walker, which handles .name). Designated ARRAY-index init {[2]=7,[4]=9} was the gap: the LOCAL scalar-array brace path (ParseCLocalDeclAST) parsed positionally only and errored on [. Now handles [k]=, unsized-array sizing to the max touched index, mixed designated+positional, and GNU range [lo ... hi]=. gcc-verified, test/carray_designated_init_b211.c → exit 42, self-host byte-identical, conformance 219/0/1. (v181; also see [[feature-c-compound-literals]] range work.) Remaining for this ticket: compound literals (struct P){3,4} / (int[]){1,2,3} as expressions — the ParseCUnary (T){...} hook + anonymous-object materialization (block-scope automatic, file-scope static). That is the self-host-fragile keystone tracked in [[feature-c-compound-literals]] (also the last blocker for c-testsuite 00216). Designated-init acceptance met; compound- literal acceptance still open.

• 2026-07-09 (A+B+C) — RECORD compound literals DONE (base + postfix + nested/ whole-value + file-scope-global-array; AN_COMPOUND_LITERAL node, defs.inc=81). sum((struct Point){3,4}) → 7, gcc-verified, tests b216-b219, self-host byte- identical, conformance 219/0/1. Full detail in [[feature-c-compound-literals]]. Remaining for this ticket: ARRAY compound literals (int[]){1,2,3} — a distinct path (array-type cast (int[]) isn't recognised by ParseCDeclType/ CIsCastAhead; needs an array temp, not a record temp). No conformance test isolates it; 00216 does not use it. Record-CL acceptance met; array-CL open.

• 2026-07-09 (A+B+C) — record-CL acceptance MET (00216 220/220, [[feature-c-compound-literals]] resolved). ARRAY compound literals (int[]){1,2,3} remain the only open item on this ticket.

RESOLVED 2026-07-09 — array compound literals landed

(int[]){1,2,3} / (elem[N]){...} implemented (CParseCompoundLiteralArr + the cast- branch abstract-array declarator + AN_INDEX-over-array-CL IR case). Both acceptance repros pass (record sum((struct Point){3,4})==7 done earlier; array (int[]){1,2,3} via pointer/arg/direct-index all gcc-verified, b226). All three original forms (designated struct-field, designated array-index, compound literals — record AND array) are done. Only unsupported edge left: STRUCT-element array literals with nested braces (struct P[]){{1,2},{3,4}} (errors cleanly, no miscompile) — a rare extension, not filed separately. Conformance 220/220. RESOLVED — moving to done.