riscv32 C import: tolerate inline asm in uncalled static inline helpers

• Type: feature (C frontend, riscv32 inline asm) — Track A.
• Filed: 2026-10-05 from ~/museum_landkaart, the ESP-IDF census.

Repro

cd ~/museum_landkaart/async && tools/idf_census.sh esp_sntp
# esp_sntp: pascal26:86: error: C: inline asm with a non-empty template is only supported on x86-64 and i386, not riscv32

(the full message and location are in build/census/esp_sntp.txt)

Why

A header import parses every static inline function in the chain. IDF's riscv helpers use asm for CSRs, fences and wfi. The app (soft-AP, SNTP, NVS, RMT) never calls them from Pascal. Option A, accept and poison: parse the asm and error only if the function is reached by codegen. Option B: real riscv32 extended asm for the common forms. A is enough for the demo.

Acceptance

tools/idf_census.sh esp_sntp gets past the asm. A Pascal call to such a helper gives a clear error (A) or works (B).

Resolution (2026-10-05)

Accept-and-poison, as asked (ProcAsmPoison in defs.inc). Inside a routine of an imported header (CHeaderMode), these are no longer errors: inline asm this target cannot read, and a call to an undeclared function (__builtin_ffs → crtl's __pxx_builtin_ffs32, absent when newlib is the libc). The routine is marked instead. Lowering a call to it refuses by name ("cannot call wrap: its body holds C inline asm ..."). A header routine that calls a poisoned one inherits the poison. The refusal sits ahead of IRInlineExpand, so it holds at -O2. __builtin_strrchr/strchr over a literal now fold (IDF's __FILENAME__). test-core rows: builtin_strrchr_fold, header_poison26.