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GRANT: compiler/builtin/builtinheap.pas → frankS, bounded to three PXXSys* wrappers

For bug-a-loadfile-runtime-wrappers-have-no-riscv32-or-xtensa-arm [A p45]. Filed at the moment it is given, because an unfiled grant is invisible to the board in both directions: it reads as covered to anyone checking permission, and as not yet done to the ranker, which then spends a dispatch re-offering finished work. Both halves were observed on 2026-08-30 — see 193a.

Scope

PXXSysOpenRO (~2192), PXXSysLseek (~2213), PXXSysClose (~2230) — riscv32 and xtensa arms only. Nothing else in the file. Anything else the work needs is a fresh ask.

The banked LoadFile codegen arm (scratchpad/rw/loadfile-xtensa.arm, 25 lines) lands in the same change as the wrappers or not at all — that constraint is frankS's own and it survives this grant. Landing the arm alone replaces error: this builtin has no arm in the xtensa backend with an empty string, which is indistinguishable from an empty file: the block was the safety property, not the obstacle.

How it was cleared — footprints, not permissions

Three lanes had an interest. Each was asked what it touches, not whether it minds.

frankA — does not touch the file at all, in either increment of feature-port-rtl-over-libc. Structural, not incidental: the four PXXSys* wrappers reach the kernel through the __pxxrawsyscall intrinsic, and the intrinsic funnels into one IR op, so the libc route changes how their calls are lowered and never their source. Same property means that ticket touches no lib/rtl file either. --rtl-libc is also x86-64-only and opt-in while this work is riscv32/xtensa, so the two do not meet even at the lowering. frankA's files: defs.inc, compiler.pas, symtab.inc, ir_codegen.inc, emit.inc.

b4 — edited the file, but everything is landed (0f0a5619a plus the amend after it), so nothing is in flight. Footprint at HEAD: const block ~206; var block ~641-668 (census counters, inside {$ifdef PXX_ALLOC_CENSUS}); PXXAlloc ~950-1095; PXXFree head ~1150; new block 1780-1895 (PXXCensusPut / PXXCensusNum / PXXCensusReport). Nearest approach ~300 lines, no textual overlap.

The one real constraint, and it is not about collisions

b4's new block sits immediately after PXXSysWrite's body (1734-1779) because it writes through it. So:

PXXCensusReport calls PXXSysWrite and runs from inside PXXAlloc. It is documented as allocating nothing for that reason.

If a new PXXSys* arm ever allocates — a managed temp, a string buffer — it re-enters the allocator, and on the threadsafe build the temp's finalize takes the heap lock the caller already holds. That is bug-a-threadsafe-plus-heap-debug-hangs-at-runtime exactly. PXXSysWrite is clean today; the constraint is on what gets added beside it. The new riscv32/xtensa arms must allocate nothing.

This is the substantive risk in the whole grant, and note that no collision check would have found it — it is a semantic adjacency, not a textual one. It surfaced only because b4 was asked what it had done rather than whether it objected.

Expiry

When the ticket resolves. Not a standing widening of Track S into compiler/builtin/**.

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