R/aaa_ffi_codegen_rules.R

In Rtinycc: Builds the 'TinyCC' Command-Line Interface and Library for 'C' Scripting in 'R'

# Rtinycc - TinyCC for R
# Copyright (C) 2025-2026 Sounkou Mahamane Toure
# SPDX-License-Identifier: GPL-3.0-or-later

# Internal lambda.r rules for codegen dispatch
#
# This file defines many small "rules" used by the code generator. Each
# rule is registered with a tiny DSL (the lambda.r style rules such as
# `ffi_input_rule`, `ffi_return_rule`, `r_to_c_return_lines_rule`, etc.)
# and returns either a string or a character vector containing C source
# lines to be injected into generated bindings. The sections below are
# grouped by purpose (input conversion, return conversion, array helpers,
# struct/union accessors, callback helpers, type mapping keys, etc.).
#
# NOTE: many groups include nearly-identical rules for multiple integer
# and floating types; these were written out explicitly for clarity.  See
# TODOs later in this file for suggestions where a small generator could
# reduce repetition by producing similar rules programmatically.

## ------------------------------------------------------------------
## FFI input conversion rules
##
## Produce C lines that convert an incoming R `SEXP` (named by `r_name`)
## into a C variable (named by `arg_name`) of the requested FFI type.
## These rules are used when generating the C thunk that bridges R -> C.
## ------------------------------------------------------------------
rtinycc_register_scalar_codegen_rules()

ffi_input_enum_rule(type_name, arg_name, r_name) %as%
  {
    sprintf("  int %s = asInteger(%s);", arg_name, r_name)
  }

ffi_input_callback_rule(type_name, arg_name, r_name) %as%
  {
    sprintf("  void* %s = R_ExternalPtrAddr(%s);", arg_name, r_name)
  }

ffi_input_rule("raw", arg_name, r_name) %as%
  {
    sprintf("  uint8_t* %s = RAW(%s);", arg_name, r_name)
  }

ffi_input_rule("integer_array", arg_name, r_name) %as%
  {
    sprintf("  int32_t* %s = INTEGER(%s);", arg_name, r_name)
  }

ffi_input_rule("numeric_array", arg_name, r_name) %as%
  {
    sprintf("  double* %s = REAL(%s);", arg_name, r_name)
  }

ffi_input_rule("logical_array", arg_name, r_name) %as%
  {
    sprintf("  int* %s = LOGICAL(%s);", arg_name, r_name)
  }

ffi_input_rule("character_array", arg_name, r_name) %as%
  {
    sprintf("  const SEXP* %s = STRING_PTR_RO(%s);", arg_name, r_name)
  }

ffi_input_rule("cstring_array", arg_name, r_name) %as%
  {
    rtinycc_render_template(
      c(
        "  if (!Rf_isString({{r_name}})) Rf_error(\"expected character vector\");",
        "  R_xlen_t _{{arg_name}}_n = XLENGTH({{r_name}});",
        "  const char** {{arg_name}} = (const char**) R_alloc((size_t)_{{arg_name}}_n, sizeof(const char*));",
        "  for (R_xlen_t _{{arg_name}}_i = 0; _{{arg_name}}_i < _{{arg_name}}_n; _{{arg_name}}_i++) {",
        "    SEXP _{{arg_name}}_elt = STRING_ELT({{r_name}}, _{{arg_name}}_i);",
        "    {{arg_name}}[_{{arg_name}}_i] = (_{{arg_name}}_elt == NA_STRING) ? NULL : Rf_translateCharUTF8(_{{arg_name}}_elt);",
        "  }"
      ),
      list(
        r_name = r_name,
        arg_name = arg_name
      )
    )
  }

ffi_input_rule(type, arg_name, r_name) %as%
  {
    stop("Unsupported FFI type: ", type, call. = FALSE)
  }

## ------------------------------------------------------------------
## Runtime `.RtinyccCall` dispatch rules
##
## Dispatch small arities directly and fall back to do.call for larger
## signatures.
## ------------------------------------------------------------------
rtinycc_call(0L, call_ptr, args) %as%
  {
    .RtinyccCall(call_ptr)
  }

rtinycc_call(1L, call_ptr, args) %as%
  {
    .RtinyccCall(call_ptr, args[[1]])
  }

rtinycc_call(2L, call_ptr, args) %as%
  {
    .RtinyccCall(call_ptr, args[[1]], args[[2]])
  }

rtinycc_call(3L, call_ptr, args) %as%
  {
    .RtinyccCall(call_ptr, args[[1]], args[[2]], args[[3]])
  }

rtinycc_call(4L, call_ptr, args) %as%
  {
    .RtinyccCall(call_ptr, args[[1]], args[[2]], args[[3]], args[[4]])
  }

rtinycc_call(5L, call_ptr, args) %as%
  {
    .RtinyccCall(
      call_ptr,
      args[[1]],
      args[[2]],
      args[[3]],
      args[[4]],
      args[[5]]
    )
  }

rtinycc_call(n_args, call_ptr, args) %as%
  {
    do.call(.RtinyccCall, c(list(call_ptr), args))
  }

## ------------------------------------------------------------------
## Runtime platform dispatch rules
##
## Keep platform-specific path/name/env branching declarative using
## lambda.r dispatch instead of large switch/if chains.
## ------------------------------------------------------------------
tcc_platform_lib_paths("Linux") %as%
  {
    c(
      "/usr/lib",
      "/usr/lib64",
      "/usr/local/lib",
      "/lib",
      "/lib64",
      "/lib32",
      "/usr/local/lib64",
      "/usr/lib/x86_64-linux-gnu",
      "/usr/lib/i386-linux-gnu",
      "/lib/x86_64-linux-gnu",
      "/lib32/x86_64-linux-gnu",
      "/lib/x86_64-linux-gnu/",
      # linux-unknown-gnu is for Alpine Linux with musl
      # which uses different library paths
      "/usr/lib/x86_64-linux-gnu",
      "/usr/lib/i386-linux-gnu",
      "/lib/x86_64-linux-gnu",
      "/lib32/x86_64-linux-gnu",
      "/usr/lib/x86_64-linux-musl",
      "/usr/lib/i386-linux-musl",
      "/lib/x86_64-linux-musl",
      "/lib32/x86_64-linux-musl",
      # amd/aarch64 multiarch paths
      "/usr/lib/amd64-linux-gnu",
      "/usr/lib/aarch64-linux-gnu"
      # manylinux paths
    )
  }

tcc_platform_lib_paths("Darwin") %as%
  {
    c(
      "/usr/lib",
      "/usr/local/lib",
      "/opt/homebrew/lib", # Apple Silicon Homebrew
      "/opt/local/lib", # MacPorts
      "/System/Library/Frameworks", # Apple system libs
      "/Library/Frameworks"
    )
  }

tcc_platform_lib_paths("Windows") %as%
  {
    sysroot <- Sys.getenv("SystemRoot", unset = "C:/Windows")
    r_bin <- file.path(R.home(), "bin")
    r_arch_bin <- file.path(R.home(), "bin", .Platform$r_arch)
    path_dirs <- strsplit(
      Sys.getenv("PATH", ""),
      .Platform$path.sep,
      fixed = TRUE
    )[[1]]

    unique(c(
      "C:/msys64/mingw64/lib", # MSYS2
      "C:/msys64/mingw32/lib",
      "C:/Rtools45/mingw_64/lib", # Rtools
      "C:/Rtools45/mingw_32/lib",
      "C:/Rtools44/mingw_64/lib", # Rtools
      "C:/Rtools44/mingw_32/lib",
      # Native Windows loader locations / common runtime dirs
      file.path(sysroot, "System32"),
      file.path(sysroot, "SysWOW64"),
      r_bin,
      r_arch_bin,
      # User/runtime PATH entries (non-Rtools setups)
      path_dirs
    ))
  }

tcc_platform_lib_paths(sysname) %as%
  {
    c("/usr/lib", "/usr/local/lib")
  }

tcc_short_lib_filename("Linux", name) %as%
  {
    paste0("lib", name, ".so")
  }

tcc_short_lib_filename("Darwin", name) %as%
  {
    paste0("lib", name, ".dylib")
  }

tcc_short_lib_filename("Windows", name) %as%
  {
    paste0(name, ".dll")
  }

tcc_short_lib_filename(sysname, name) %as%
  {
    paste0("lib", name, ".so")
  }

tcc_output_type_rule("memory") %as% 1L
tcc_output_type_rule("obj") %as% 3L
tcc_output_type_rule("dll") %as% 4L
tcc_output_type_rule("exe") %as% 2L
tcc_output_type_rule("preprocess") %as% 5L

tcc_loader_env_key("Windows") %as% "PATH"
tcc_loader_env_key("Darwin") %as% "DYLD_LIBRARY_PATH"
tcc_loader_env_key(sysname) %as% "LD_LIBRARY_PATH"

tcc_loader_env_sep("Windows") %as% .Platform$path.sep
tcc_loader_env_sep(sysname) %as% ":"

## ------------------------------------------------------------------
## FFI return conversion rules
##
## Produce C code that converts a C expression (`value_expr`) into an
## R `SEXP` return value. Used when generating the C -> R return thunk.
## ------------------------------------------------------------------
ffi_return_enum_rule(type_name, value_expr) %as%
  {
    sprintf("return ScalarInteger((int)%s);", value_expr)
  }

ffi_return_rule(type, value_expr) %as%
  {
    stop("Unsupported FFI return type: ", type, call. = FALSE)
  }

## ------------------------------------------------------------------
## Array return helpers
##
## Helper rules for allocating an R vector to hold array returns and for
## copying C buffers into the newly allocated R vector (`out`).
## ------------------------------------------------------------------
array_return_alloc_line_rule("raw", len_name) %as%
  {
    sprintf("SEXP out = PROTECT(allocVector(RAWSXP, %s));", len_name)
  }

array_return_alloc_line_rule("integer_array", len_name) %as%
  {
    sprintf("SEXP out = PROTECT(allocVector(INTSXP, %s));", len_name)
  }

array_return_alloc_line_rule("numeric_array", len_name) %as%
  {
    sprintf("SEXP out = PROTECT(allocVector(REALSXP, %s));", len_name)
  }

array_return_alloc_line_rule("logical_array", len_name) %as%
  {
    sprintf("SEXP out = PROTECT(allocVector(LGLSXP, %s));", len_name)
  }

array_return_alloc_line_rule(type, len_name) %as%
  {
    stop("Unsupported array return type: ", type, call. = FALSE)
  }

array_return_copy_line_rule("raw", len_name, value_expr) %as%
  {
    sprintf(
      "  if (%s > 0) memcpy(RAW(out), %s, sizeof(uint8_t) * %s);",
      len_name,
      value_expr,
      len_name
    )
  }

array_return_copy_line_rule("integer_array", len_name, value_expr) %as%
  {
    sprintf(
      "  if (%s > 0) memcpy(INTEGER(out), %s, sizeof(int32_t) * %s);",
      len_name,
      value_expr,
      len_name
    )
  }

array_return_copy_line_rule("numeric_array", len_name, value_expr) %as%
  {
    sprintf(
      "  if (%s > 0) memcpy(REAL(out), %s, sizeof(double) * %s);",
      len_name,
      value_expr,
      len_name
    )
  }

array_return_copy_line_rule("logical_array", len_name, value_expr) %as%
  {
    sprintf(
      "  if (%s > 0) memcpy(LOGICAL(out), %s, sizeof(int) * %s);",
      len_name,
      value_expr,
      len_name
    )
  }

array_return_copy_line_rule(type, len_name, value_expr) %as%
  {
    stop("Unsupported array return type: ", type, call. = FALSE)
  }

## ------------------------------------------------------------------
## Struct field getter rules
##
## Produce code that reads a field from a C struct (pointer `p`) and
## converts it into an R `SEXP` for consumer code. Rules are repeated
## for multiple primitive types for clarity and explicit handling.
## ------------------------------------------------------------------
struct_field_getter_rule("i8", field_name) %as%
  {
    sprintf("return ScalarInteger((int)p->%s);", field_name)
  }

struct_field_getter_rule("i16", field_name) %as%
  {
    sprintf("return ScalarInteger((int)p->%s);", field_name)
  }

struct_field_getter_rule("i32", field_name) %as%
  {
    sprintf("return ScalarInteger(p->%s);", field_name)
  }

struct_field_getter_rule("i64", field_name) %as%
  {
    c(
      sprintf("  int64_t __rtinycc_ret = p->%s;", field_name),
      "  if (__rtinycc_ret > INT64_C(9007199254740992) || __rtinycc_ret < -INT64_C(9007199254740992)) Rf_warning(\"i64 precision loss in R numeric\");",
      "  return ScalarReal((double)__rtinycc_ret);"
    )
  }

struct_field_getter_rule("u8", field_name) %as%
  {
    sprintf("return ScalarInteger((int)p->%s);", field_name)
  }

struct_field_getter_rule("u16", field_name) %as%
  {
    sprintf("return ScalarInteger((int)p->%s);", field_name)
  }

struct_field_getter_rule("u32", field_name) %as%
  {
    sprintf("return ScalarReal((double)p->%s);", field_name)
  }

struct_field_getter_rule("u64", field_name) %as%
  {
    c(
      sprintf("  uint64_t __rtinycc_ret = p->%s;", field_name),
      "  if (__rtinycc_ret > UINT64_C(9007199254740992)) Rf_warning(\"u64 precision loss in R numeric\");",
      "  return ScalarReal((double)__rtinycc_ret);"
    )
  }

struct_field_getter_rule("f32", field_name) %as%
  {
    sprintf("return ScalarReal((double)p->%s);", field_name)
  }

struct_field_getter_rule("f64", field_name) %as%
  {
    sprintf("return ScalarReal(p->%s);", field_name)
  }

struct_field_getter_rule("bool", field_name) %as%
  {
    sprintf("return ScalarLogical((int)p->%s);", field_name)
  }

struct_field_getter_rule("cstring", field_name) %as%
  {
    c(
      sprintf("  if (p->%s) {", field_name),
      sprintf("    SEXP out = PROTECT(mkString(p->%s));", field_name),
      "    UNPROTECT(1);",
      "    return out;",
      "  } else {",
      "    return R_NilValue;",
      "  }"
    )
  }

struct_field_getter_rule("ptr", field_name) %as%
  {
    sprintf(
      "return RC_make_borrowed_view(p->%s, Rf_install(\"rtinycc_borrowed\"), ext);",
      field_name
    )
  }

struct_field_getter_rule(type_name, field_name) %as%
  {
    sprintf(
      "return RC_make_borrowed_view(&p->%s, Rf_install(\"rtinycc_borrowed\"), ext);",
      field_name
    )
  }

## ------------------------------------------------------------------
## Struct array field getter rules
##
## Like the struct field getters, but for array fields inside structs
## (access element `idx`). Returns an R scalar for the selected element.
## ------------------------------------------------------------------
struct_array_field_getter_rule("i8", field_name) %as%
  {
    sprintf("return ScalarInteger((int)p->%s[idx]);", field_name)
  }

struct_array_field_getter_rule("i16", field_name) %as%
  {
    sprintf("return ScalarInteger((int)p->%s[idx]);", field_name)
  }

struct_array_field_getter_rule("i32", field_name) %as%
  {
    sprintf("return ScalarInteger(p->%s[idx]);", field_name)
  }

struct_array_field_getter_rule("i64", field_name) %as%
  {
    c(
      sprintf("  int64_t __rtinycc_ret = p->%s[idx];", field_name),
      "  if (__rtinycc_ret > INT64_C(9007199254740992) || __rtinycc_ret < -INT64_C(9007199254740992)) Rf_warning(\"i64 precision loss in R numeric\");",
      "  return ScalarReal((double)__rtinycc_ret);"
    )
  }

struct_array_field_getter_rule("u8", field_name) %as%
  {
    sprintf("return ScalarInteger((int)p->%s[idx]);", field_name)
  }

struct_array_field_getter_rule("u16", field_name) %as%
  {
    sprintf("return ScalarInteger((int)p->%s[idx]);", field_name)
  }

struct_array_field_getter_rule("u32", field_name) %as%
  {
    sprintf("return ScalarReal((double)p->%s[idx]);", field_name)
  }

struct_array_field_getter_rule("u64", field_name) %as%
  {
    c(
      sprintf("  uint64_t __rtinycc_ret = p->%s[idx];", field_name),
      "  if (__rtinycc_ret > UINT64_C(9007199254740992)) Rf_warning(\"u64 precision loss in R numeric\");",
      "  return ScalarReal((double)__rtinycc_ret);"
    )
  }

struct_array_field_getter_rule("f32", field_name) %as%
  {
    sprintf("return ScalarReal((double)p->%s[idx]);", field_name)
  }

struct_array_field_getter_rule("f64", field_name) %as%
  {
    sprintf("return ScalarReal(p->%s[idx]);", field_name)
  }

struct_array_field_getter_rule("bool", field_name) %as%
  {
    sprintf("return ScalarLogical((int)p->%s[idx]);", field_name)
  }

struct_array_field_getter_rule(type_name, field_name) %as%
  {
    sprintf("return ScalarInteger((int)p->%s[idx]);", field_name)
  }

## ------------------------------------------------------------------
## Struct array field setter rules
##
## Generate code to set an element of an array field inside a struct
## from an R `SEXP` value (named `val`).
## ------------------------------------------------------------------
struct_array_field_setter_rule("i8", field_name) %as%
  {
    sprintf("p->%s[idx] = (int8_t)asInteger(val);", field_name)
  }

struct_array_field_setter_rule("i16", field_name) %as%
  {
    sprintf("p->%s[idx] = (int16_t)asInteger(val);", field_name)
  }

struct_array_field_setter_rule("i32", field_name) %as%
  {
    sprintf("p->%s[idx] = asInteger(val);", field_name)
  }

struct_array_field_setter_rule("i64", field_name) %as%
  {
    sprintf("p->%s[idx] = (int64_t)REAL(val)[0];", field_name)
  }

struct_array_field_setter_rule("u8", field_name) %as%
  {
    sprintf("p->%s[idx] = (uint8_t)asInteger(val);", field_name)
  }

struct_array_field_setter_rule("u16", field_name) %as%
  {
    sprintf("p->%s[idx] = (uint16_t)asInteger(val);", field_name)
  }

struct_array_field_setter_rule("u32", field_name) %as%
  {
    sprintf("p->%s[idx] = (uint32_t)REAL(val)[0];", field_name)
  }

struct_array_field_setter_rule("u64", field_name) %as%
  {
    sprintf("p->%s[idx] = (uint64_t)REAL(val)[0];", field_name)
  }

struct_array_field_setter_rule("f32", field_name) %as%
  {
    sprintf("p->%s[idx] = (float)REAL(val)[0];", field_name)
  }

struct_array_field_setter_rule("f64", field_name) %as%
  {
    sprintf("p->%s[idx] = REAL(val)[0];", field_name)
  }

struct_array_field_setter_rule("bool", field_name) %as%
  {
    sprintf("p->%s[idx] = (bool)asLogical(val);", field_name)
  }

struct_array_field_setter_rule(type_name, field_name) %as%
  {
    sprintf("p->%s[idx] = (uint8_t)asInteger(val);", field_name)
  }

## ------------------------------------------------------------------
## Struct field setter rules
##
## Produce code that assigns an R value (`val`) into a struct field
## (handles scalar fields and fixed-size char arrays). These are the
## counterparts to the getter rules above.
## ------------------------------------------------------------------
struct_field_setter_rule("i8", field_name, size) %as%
  {
    sprintf("p->%s = (int8_t)asInteger(val);", field_name)
  }

struct_field_setter_rule("i16", field_name, size) %as%
  {
    sprintf("p->%s = (int16_t)asInteger(val);", field_name)
  }

struct_field_setter_rule("i32", field_name, size) %as%
  {
    sprintf("p->%s = asInteger(val);", field_name)
  }

struct_field_setter_rule("i64", field_name, size) %as%
  {
    sprintf("p->%s = (int64_t)REAL(val)[0];", field_name)
  }

struct_field_setter_rule("u8", field_name, size) %as%
  {
    sprintf("p->%s = (uint8_t)asInteger(val);", field_name)
  }

struct_field_setter_rule("u16", field_name, size) %as%
  {
    sprintf("p->%s = (uint16_t)asInteger(val);", field_name)
  }

struct_field_setter_rule("u32", field_name, size) %as%
  {
    sprintf("p->%s = (uint32_t)REAL(val)[0];", field_name)
  }

struct_field_setter_rule("u64", field_name, size) %as%
  {
    sprintf("p->%s = (uint64_t)REAL(val)[0];", field_name)
  }

struct_field_setter_rule("f32", field_name, size) %as%
  {
    sprintf("p->%s = (float)asReal(val);", field_name)
  }

struct_field_setter_rule("f64", field_name, size) %as%
  {
    sprintf("p->%s = asReal(val);", field_name)
  }

struct_field_setter_rule("bool", field_name, size) %as%
  {
    sprintf("p->%s = (bool)asLogical(val);", field_name)
  }

struct_field_setter_rule("ptr", field_name, size) %as%
  {
    sprintf("p->%s = R_ExternalPtrAddr(val);", field_name)
  }

struct_field_setter_rule("cstring", field_name, size) %as%
  {
    if (!is.null(size)) {
      return(c(
        "  const char *src = CHAR(STRING_ELT(val, 0));",
        sprintf("  strncpy(p->%s, src, %d);", field_name, size - 1),
        sprintf("  p->%s[%d] = '\\0';", field_name, size - 1)
      ))
    }
    sprintf("p->%s = CHAR(STRING_ELT(val, 0));", field_name)
  }

struct_field_setter_rule(type_name, field_name, size) %as%
  {
    sprintf("// Cannot set field of type %s", type_name)
  }

## ------------------------------------------------------------------
## Union field helper rules
##
## Unions are represented by mapping to the corresponding struct rules
## wherever possible; setting array members in unions is unsupported and
## emits placeholder comments. These rules delegate to struct helpers.
## ------------------------------------------------------------------
union_field_getter_rule(type_name, mem_name) %as%
  {
    struct_field_getter_rule(type_name, mem_name)
  }

union_field_setter_rule("raw", mem_name, size) %as%
  {
    sprintf("// Cannot set union member array type raw")
  }

union_field_setter_rule("integer_array", mem_name, size) %as%
  {
    sprintf("// Cannot set union member array type integer_array")
  }

union_field_setter_rule("numeric_array", mem_name, size) %as%
  {
    sprintf("// Cannot set union member array type numeric_array")
  }

union_field_setter_rule("logical_array", mem_name, size) %as%
  {
    sprintf("// Cannot set union member array type logical_array")
  }

union_field_setter_rule("character_array", mem_name, size) %as%
  {
    sprintf("// Cannot set union member array type character_array")
  }

union_field_setter_rule("cstring_array", mem_name, size) %as%
  {
    sprintf("// Cannot set union member array type cstring_array")
  }

union_field_setter_rule(type_name, mem_name, size) %as%
  {
    struct_field_setter_rule(type_name, mem_name, size)
  }

## ------------------------------------------------------------------
## Callback argument kind/value helpers
##
## Map a callback argument type to an internal CB_ARG_* kind and to the
## field name that holds the value inside the generic callback value
## union struct used by the runtime. These are small lookup rules used
## when generating callback trampoline code.
## ------------------------------------------------------------------
cb_arg_kind_rule("ptr") %as%
  {
    "CB_ARG_PTR"
  }

cb_arg_kind_rule("cstring") %as%
  {
    "CB_ARG_CSTRING"
  }

cb_arg_kind_rule("real") %as%
  {
    "CB_ARG_REAL"
  }

cb_arg_kind_rule("logical") %as%
  {
    "CB_ARG_LOGICAL"
  }

cb_arg_kind_rule("int") %as%
  {
    "CB_ARG_INT"
  }

cb_arg_value_rule("ptr", arg_expr) %as%
  {
    list(field = "p", expr = arg_expr)
  }

cb_arg_value_rule("cstring", arg_expr) %as%
  {
    list(field = "s", expr = arg_expr)
  }

cb_arg_value_rule("real", arg_expr) %as%
  {
    list(field = "d", expr = arg_expr)
  }

cb_arg_value_rule("logical", arg_expr) %as%
  {
    list(field = "i", expr = arg_expr)
  }

cb_arg_value_rule("int", arg_expr) %as%
  {
    list(field = "i", expr = arg_expr)
  }

## ------------------------------------------------------------------
## C default return helpers
##
## When a callback or conversion fails we need a sensible C-level default
## return statement for a given C type. These helpers emit appropriately
## indented return lines (used by many `r_to_c_return_lines_rule` cases).
## ------------------------------------------------------------------
c_default_return_rule("void", indent) %as%
  {
    pad <- paste(rep(" ", indent), collapse = "")
    paste0(pad, "return;")
  }

c_default_return_rule("sexp", indent) %as%
  {
    pad <- paste(rep(" ", indent), collapse = "")
    paste0(pad, "return R_NilValue;")
  }

c_default_return_rule("ptr", indent) %as%
  {
    pad <- paste(rep(" ", indent), collapse = "")
    paste0(pad, "return NULL;")
  }

c_default_return_rule("cstring", indent) %as%
  {
    pad <- paste(rep(" ", indent), collapse = "")
    paste0(pad, "return NULL;")
  }

c_default_return_rule("real", indent) %as%
  {
    pad <- paste(rep(" ", indent), collapse = "")
    paste0(pad, "return NA_REAL;")
  }

c_default_return_rule("logical", indent) %as%
  {
    pad <- paste(rep(" ", indent), collapse = "")
    paste0(pad, "return -1;")
  }

c_default_return_rule("int", indent) %as%
  {
    pad <- paste(rep(" ", indent), collapse = "")
    paste0(pad, "return NA_INTEGER;")
  }

## ------------------------------------------------------------------
## C <-> SEXP type name helpers
##
## Map between C types used in generated stubs and the canonical names
## used for selecting conversion rules and SEXP constructors.
## ------------------------------------------------------------------
c_sexp_type_rule("ptr") %as%
  {
    "void*"
  }

c_sexp_type_rule("int") %as%
  {
    "int"
  }

c_sexp_type_rule("longlong") %as%
  {
    "long long"
  }

c_sexp_type_rule("real") %as%
  {
    "double"
  }

c_sexp_type_rule("cstring") %as%
  {
    "const char*"
  }

c_sexp_type_rule("bool") %as%
  {
    "bool"
  }

## ------------------------------------------------------------------
## Canonical R-facing type keys
##
## Map C types into the compact R-facing type keys (e.g. "i32", "f64",
## "ptr") used across many rule lookups.
## ------------------------------------------------------------------
c_r_type_rule("ptr") %as%
  {
    "ptr"
  }

c_r_type_rule("i32") %as%
  {
    "i32"
  }

c_r_type_rule("f64") %as%
  {
    "f64"
  }

c_r_type_rule("cstring") %as%
  {
    "cstring"
  }

c_r_type_rule("bool") %as%
  {
    "bool"
  }

c_r_type_rule("void") %as%
  {
    "void"
  }

c_r_type_rule("sexp") %as%
  {
    "sexp"
  }

## ------------------------------------------------------------------
## SEXP constructor helpers
##
## Provide the name of the constructor (or the full call form) used to
## create a SEXP from a native C value during return conversion.
## ------------------------------------------------------------------
sexp_constructor_rule("ptr") %as%
  {
    "R_MakeExternalPtr"
  }

sexp_constructor_rule("int") %as%
  {
    "ScalarInteger"
  }

sexp_constructor_rule("real") %as%
  {
    "ScalarReal"
  }

sexp_constructor_rule("cstring") %as%
  {
    "mkString"
  }

sexp_constructor_rule("bool") %as%
  {
    "ScalarLogical"
  }

sexp_constructor_rule("sexp") %as%
  {
    "identity"
  }

## ------------------------------------------------------------------
## SEXP constructor call forms
##
## Produce the string of C code to call the SEXP constructor for a given
## expression (used when building return expressions inline).
## ------------------------------------------------------------------
sexp_constructor_call_rule("ptr", arg_expr) %as%
  {
    sprintf("RC_make_unowned_ptr(%s, R_NilValue)", arg_expr)
  }

sexp_constructor_call_rule("cstring", arg_expr) %as%
  {
    sprintf(
      "({ const char* __rtinycc_tmp = %s; __rtinycc_tmp ? mkString(__rtinycc_tmp) : R_NilValue; })",
      arg_expr
    )
  }

sexp_constructor_call_rule("int", arg_expr) %as%
  {
    sprintf("ScalarInteger(%s)", arg_expr)
  }

sexp_constructor_call_rule("real", arg_expr) %as%
  {
    sprintf("ScalarReal(%s)", arg_expr)
  }

sexp_constructor_call_rule("bool", arg_expr) %as%
  {
    sprintf("ScalarLogical(%s)", arg_expr)
  }

sexp_constructor_call_rule("sexp", arg_expr) %as%
  {
    sprintf("%s", arg_expr)
  }

## ------------------------------------------------------------------
## R -> C converter helpers
##
## Provide the simple converter function name used to extract C values
## from R `SEXP` objects (e.g. `asInteger`, `asReal`, `R_ExternalPtrAddr`).
## ------------------------------------------------------------------
r_to_c_converter_rule("ptr") %as%
  {
    "R_ExternalPtrAddr"
  }

r_to_c_converter_rule("int") %as%
  {
    "asInteger"
  }

r_to_c_converter_rule("real") %as%
  {
    "asReal"
  }

r_to_c_converter_rule("cstring") %as%
  {
    "CHAR"
  }

r_to_c_converter_rule("bool") %as%
  {
    "asLogical"
  }

r_to_c_converter_rule("sexp") %as%
  {
    "identity"
  }

## ------------------------------------------------------------------
## R -> C return conversion lines
##
## These rules emit one or more lines of C that validate and convert
## a returned R `SEXP` (from a callback) into the expected C return
## value. They handle NA/NA_REAL checks, range checks, and emit warnings
## and default returns on error.
## ------------------------------------------------------------------
r_to_c_return_lines_rule("void", c_type, result_var, indent) %as%
  {
    pad <- paste(rep(" ", indent), collapse = "")
    paste0(pad, "return;")
  }

r_to_c_return_lines_rule("sexp", c_type, result_var, indent) %as%
  {
    pad <- paste(rep(" ", indent), collapse = "")
    paste0(pad, "return ", result_var, ";")
  }

r_to_c_return_lines_rule("ptr", c_type, result_var, indent) %as%
  {
    pad <- paste(rep(" ", indent), collapse = "")
    paste0(pad, "return R_ExternalPtrAddr(", result_var, ");")
  }

r_to_c_return_lines_rule("cstring", c_type, result_var, indent) %as%
  {
    pad <- paste(rep(" ", indent), collapse = "")
    c(
      paste0(pad, "if (", result_var, " == R_NilValue) return NULL;"),
      paste0(
        pad,
        "if (!Rf_isString(",
        result_var,
        ") || XLENGTH(",
        result_var,
        ") < 1) {"
      ),
      paste0(pad, "  Rf_warning(\"callback returned non-string\");"),
      paste0(pad, "  return NULL;"),
      paste0(pad, "}"),
      paste0(pad, "SEXP _str = STRING_ELT(", result_var, ", 0);"),
      paste0(pad, "if (_str == NA_STRING) return NULL;"),
      paste0(pad, "return Rf_translateCharUTF8(_str);")
    )
  }

r_to_c_return_lines_rule("bool", c_type, result_var, indent) %as%
  {
    pad <- paste(rep(" ", indent), collapse = "")
    default_line <- get_c_default_return(c_type, indent = indent)
    c(
      paste0(pad, "int _v = asLogical(", result_var, ");"),
      paste0(pad, "if (_v == NA_LOGICAL) {"),
      paste0(pad, "  Rf_warning(\"callback returned NA logical\");"),
      default_line,
      paste0(pad, "}"),
      paste0(pad, "return (_v != 0);")
    )
  }

r_to_c_return_lines_rule("i8", c_type, result_var, indent) %as%
  {
    pad <- paste(rep(" ", indent), collapse = "")
    default_line <- get_c_default_return(c_type, indent = indent)
    c(
      paste0(pad, "int _v = asInteger(", result_var, ");"),
      paste0(pad, "if (_v == NA_INTEGER) {"),
      paste0(pad, "  Rf_warning(\"callback returned NA integer\");"),
      default_line,
      paste0(pad, "}"),
      paste0(pad, "if (_v < INT8_MIN || _v > INT8_MAX) {"),
      paste0(pad, "  Rf_warning(\"callback returned out-of-range i8\");"),
      default_line,
      paste0(pad, "}"),
      paste0(pad, "return (int8_t)_v;")
    )
  }

r_to_c_return_lines_rule("i16", c_type, result_var, indent) %as%
  {
    pad <- paste(rep(" ", indent), collapse = "")
    default_line <- get_c_default_return(c_type, indent = indent)
    c(
      paste0(pad, "int _v = asInteger(", result_var, ");"),
      paste0(pad, "if (_v == NA_INTEGER) {"),
      paste0(pad, "  Rf_warning(\"callback returned NA integer\");"),
      default_line,
      paste0(pad, "}"),
      paste0(pad, "if (_v < INT16_MIN || _v > INT16_MAX) {"),
      paste0(pad, "  Rf_warning(\"callback returned out-of-range i16\");"),
      default_line,
      paste0(pad, "}"),
      paste0(pad, "return (int16_t)_v;")
    )
  }

r_to_c_return_lines_rule("i32", c_type, result_var, indent) %as%
  {
    pad <- paste(rep(" ", indent), collapse = "")
    default_line <- get_c_default_return(c_type, indent = indent)
    c(
      paste0(pad, "int _v = asInteger(", result_var, ");"),
      paste0(pad, "if (_v == NA_INTEGER) {"),
      paste0(pad, "  Rf_warning(\"callback returned NA integer\");"),
      default_line,
      paste0(pad, "}"),
      paste0(pad, "return (int32_t)_v;")
    )
  }

r_to_c_return_lines_rule("int", c_type, result_var, indent) %as%
  {
    pad <- paste(rep(" ", indent), collapse = "")
    default_line <- get_c_default_return(c_type, indent = indent)
    c(
      paste0(pad, "int _v = asInteger(", result_var, ");"),
      paste0(pad, "if (_v == NA_INTEGER) {"),
      paste0(pad, "  Rf_warning(\"callback returned NA integer\");"),
      default_line,
      paste0(pad, "}"),
      paste0(pad, "return _v;")
    )
  }

r_to_c_return_lines_rule("u8", c_type, result_var, indent) %as%
  {
    pad <- paste(rep(" ", indent), collapse = "")
    default_line <- get_c_default_return(c_type, indent = indent)
    c(
      paste0(pad, "int _v = asInteger(", result_var, ");"),
      paste0(pad, "if (_v == NA_INTEGER) {"),
      paste0(pad, "  Rf_warning(\"callback returned NA integer\");"),
      default_line,
      paste0(pad, "}"),
      paste0(pad, "if (_v < 0 || _v > UINT8_MAX) {"),
      paste0(pad, "  Rf_warning(\"callback returned out-of-range u8\");"),
      default_line,
      paste0(pad, "}"),
      paste0(pad, "return (uint8_t)_v;")
    )
  }

r_to_c_return_lines_rule("u16", c_type, result_var, indent) %as%
  {
    pad <- paste(rep(" ", indent), collapse = "")
    default_line <- get_c_default_return(c_type, indent = indent)
    c(
      paste0(pad, "int _v = asInteger(", result_var, ");"),
      paste0(pad, "if (_v == NA_INTEGER) {"),
      paste0(pad, "  Rf_warning(\"callback returned NA integer\");"),
      default_line,
      paste0(pad, "}"),
      paste0(pad, "if (_v < 0 || _v > UINT16_MAX) {"),
      paste0(pad, "  Rf_warning(\"callback returned out-of-range u16\");"),
      default_line,
      paste0(pad, "}"),
      paste0(pad, "return (uint16_t)_v;")
    )
  }

r_to_c_return_lines_rule("u32", c_type, result_var, indent) %as%
  {
    pad <- paste(rep(" ", indent), collapse = "")
    default_line <- get_c_default_return(c_type, indent = indent)
    c(
      paste0(pad, "double _v = asReal(", result_var, ");"),
      paste0(pad, "if (ISNA(_v) || ISNAN(_v)) {"),
      paste0(pad, "  Rf_warning(\"callback returned NA numeric\");"),
      default_line,
      paste0(pad, "}"),
      paste0(pad, "if (_v < 0 || _v > (double)UINT32_MAX) {"),
      paste0(pad, "  Rf_warning(\"callback returned out-of-range u32\");"),
      default_line,
      paste0(pad, "}"),
      paste0(pad, "if (trunc(_v) != _v) {"),
      paste0(pad, "  Rf_warning(\"callback returned non-integer numeric\");"),
      default_line,
      paste0(pad, "}"),
      paste0(pad, "return (uint32_t)_v;")
    )
  }

r_to_c_return_lines_rule("i64", c_type, result_var, indent) %as%
  {
    pad <- paste(rep(" ", indent), collapse = "")
    default_line <- get_c_default_return(c_type, indent = indent)
    c(
      paste0(pad, "double _v = asReal(", result_var, ");"),
      paste0(pad, "if (ISNA(_v) || ISNAN(_v)) {"),
      paste0(pad, "  Rf_warning(\"callback returned NA numeric\");"),
      default_line,
      paste0(pad, "}"),
      paste0(pad, "if (fabs(_v) > 9007199254740992.0) {"),
      paste0(
        pad,
        "  Rf_warning(\"callback i64 precision loss in R numeric\");"
      ),
      default_line,
      paste0(pad, "}"),
      paste0(pad, "if (trunc(_v) != _v) {"),
      paste0(pad, "  Rf_warning(\"callback returned non-integer numeric\");"),
      default_line,
      paste0(pad, "}"),
      paste0(pad, "if (_v < (double)INT64_MIN || _v > (double)INT64_MAX) {"),
      paste0(pad, "  Rf_warning(\"callback returned out-of-range i64\");"),
      default_line,
      paste0(pad, "}"),
      paste0(pad, "return (int64_t)_v;")
    )
  }

r_to_c_return_lines_rule("u64", c_type, result_var, indent) %as%
  {
    pad <- paste(rep(" ", indent), collapse = "")
    default_line <- get_c_default_return(c_type, indent = indent)
    c(
      paste0(pad, "double _v = asReal(", result_var, ");"),
      paste0(pad, "if (ISNA(_v) || ISNAN(_v)) {"),
      paste0(pad, "  Rf_warning(\"callback returned NA numeric\");"),
      default_line,
      paste0(pad, "}"),
      paste0(pad, "if (_v < 0) {"),
      paste0(pad, "  Rf_warning(\"callback returned out-of-range u64\");"),
      default_line,
      paste0(pad, "}"),
      paste0(pad, "if (fabs(_v) > 9007199254740992.0) {"),
      paste0(
        pad,
        "  Rf_warning(\"callback u64 precision loss in R numeric\");"
      ),
      default_line,
      paste0(pad, "}"),
      paste0(pad, "if (trunc(_v) != _v) {"),
      paste0(pad, "  Rf_warning(\"callback returned non-integer numeric\");"),
      default_line,
      paste0(pad, "}"),
      paste0(pad, "if (_v > (double)UINT64_MAX) {"),
      paste0(pad, "  Rf_warning(\"callback returned out-of-range u64\");"),
      default_line,
      paste0(pad, "}"),
      paste0(pad, "return (uint64_t)_v;")
    )
  }

r_to_c_return_lines_rule("double", c_type, result_var, indent) %as%
  {
    pad <- paste(rep(" ", indent), collapse = "")
    default_line <- get_c_default_return(c_type, indent = indent)
    c(
      paste0(pad, "double _v = asReal(", result_var, ");"),
      paste0(pad, "if (ISNA(_v) || ISNAN(_v)) {"),
      paste0(pad, "  Rf_warning(\"callback returned NA numeric\");"),
      default_line,
      paste0(pad, "}"),
      paste0(pad, "return _v;")
    )
  }

r_to_c_return_lines_rule("float", c_type, result_var, indent) %as%
  {
    pad <- paste(rep(" ", indent), collapse = "")
    default_line <- get_c_default_return(c_type, indent = indent)
    c(
      paste0(pad, "double _v = asReal(", result_var, ");"),
      paste0(pad, "if (ISNA(_v) || ISNAN(_v)) {"),
      paste0(pad, "  Rf_warning(\"callback returned NA numeric\");"),
      default_line,
      paste0(pad, "}"),
      paste0(pad, "return (float)_v;")
    )
  }

## ------------------------------------------------------------------
## Callback kind key mapping
##
## Map C types (and pointer-ness) to the compact kinds used by the
## callback trampoline generator (ptr, cstring, real, logical, int).
## ------------------------------------------------------------------
cb_kind_key_rule(type_name, TRUE) %as%
  {
    "ptr"
  }
cb_kind_key_rule("void*", FALSE) %as%
  {
    "ptr"
  }
cb_kind_key_rule("void *", FALSE) %as%
  {
    "ptr"
  }
cb_kind_key_rule("ptr", FALSE) %as%
  {
    "ptr"
  }
cb_kind_key_rule("char*", FALSE) %as%
  {
    "cstring"
  }
cb_kind_key_rule("const char*", FALSE) %as%
  {
    "cstring"
  }
cb_kind_key_rule("string", FALSE) %as%
  {
    "cstring"
  }
cb_kind_key_rule("cstring", FALSE) %as%
  {
    "cstring"
  }
cb_kind_key_rule("double", FALSE) %as%
  {
    "real"
  }
cb_kind_key_rule("float", FALSE) %as%
  {
    "real"
  }
cb_kind_key_rule("f64", FALSE) %as%
  {
    "real"
  }
cb_kind_key_rule("f32", FALSE) %as%
  {
    "real"
  }
cb_kind_key_rule("int64_t", FALSE) %as%
  {
    "real"
  }
cb_kind_key_rule("i64", FALSE) %as%
  {
    "real"
  }
cb_kind_key_rule("uint32_t", FALSE) %as%
  {
    "real"
  }
cb_kind_key_rule("u32", FALSE) %as%
  {
    "real"
  }
cb_kind_key_rule("uint64_t", FALSE) %as%
  {
    "real"
  }
cb_kind_key_rule("u64", FALSE) %as%
  {
    "real"
  }
cb_kind_key_rule("bool", FALSE) %as%
  {
    "logical"
  }
cb_kind_key_rule("_Bool", FALSE) %as%
  {
    "logical"
  }
cb_kind_key_rule(type_name, is_ptr) %as%
  {
    "int"
  }

## ------------------------------------------------------------------
## C-to-R type key map for arguments
##
## These rules map C type spellings (and pointer-ness) to the canonical
## R-facing type key used across code generation (e.g. "i32", "f64",
## "ptr"). This centralizes many small spelling variants in one place.
## ------------------------------------------------------------------
c_r_key_rule(type_name, TRUE) %as%
  {
    "ptr"
  }
c_r_key_rule("void*", FALSE) %as%
  {
    "ptr"
  }
c_r_key_rule("void *", FALSE) %as%
  {
    "ptr"
  }
c_r_key_rule("ptr", FALSE) %as%
  {
    "ptr"
  }
c_r_key_rule("int", FALSE) %as%
  {
    "i32"
  }
c_r_key_rule("int32_t", FALSE) %as%
  {
    "i32"
  }
c_r_key_rule("i32", FALSE) %as%
  {
    "i32"
  }
c_r_key_rule("int16_t", FALSE) %as%
  {
    "i32"
  }
c_r_key_rule("i16", FALSE) %as%
  {
    "i32"
  }
c_r_key_rule("int8_t", FALSE) %as%
  {
    "i32"
  }
c_r_key_rule("i8", FALSE) %as%
  {
    "i32"
  }
c_r_key_rule("long", FALSE) %as%
  {
    "i32"
  }
c_r_key_rule("long long", FALSE) %as%
  {
    "i32"
  }
c_r_key_rule("int64_t", FALSE) %as%
  {
    "i32"
  }
c_r_key_rule("i64", FALSE) %as%
  {
    "i32"
  }
c_r_key_rule("uint8_t", FALSE) %as%
  {
    "i32"
  }
c_r_key_rule("u8", FALSE) %as%
  {
    "i32"
  }
c_r_key_rule("uint16_t", FALSE) %as%
  {
    "i32"
  }
c_r_key_rule("u16", FALSE) %as%
  {
    "i32"
  }
c_r_key_rule("uint32_t", FALSE) %as%
  {
    "i32"
  }
c_r_key_rule("u32", FALSE) %as%
  {
    "i32"
  }
c_r_key_rule("uint64_t", FALSE) %as%
  {
    "i32"
  }
c_r_key_rule("u64", FALSE) %as%
  {
    "i32"
  }
c_r_key_rule("double", FALSE) %as%
  {
    "f64"
  }
c_r_key_rule("float", FALSE) %as%
  {
    "f64"
  }
c_r_key_rule("f64", FALSE) %as%
  {
    "f64"
  }
c_r_key_rule("f32", FALSE) %as%
  {
    "f64"
  }
c_r_key_rule("char*", FALSE) %as%
  {
    "cstring"
  }
c_r_key_rule("const char*", FALSE) %as%
  {
    "cstring"
  }
c_r_key_rule("string", FALSE) %as%
  {
    "cstring"
  }
c_r_key_rule("cstring", FALSE) %as%
  {
    "cstring"
  }
c_r_key_rule("bool", FALSE) %as%
  {
    "bool"
  }
c_r_key_rule("_Bool", FALSE) %as%
  {
    "bool"
  }
c_r_key_rule("void", FALSE) %as%
  {
    "void"
  }
c_r_key_rule("SEXP", FALSE) %as%
  {
    "sexp"
  }
c_r_key_rule("sexp", FALSE) %as%
  {
    "sexp"
  }
c_r_key_rule(type_name, is_ptr) %as%
  {
    "ptr"
  }

## ------------------------------------------------------------------
## SEXP constructor key mapping
##
## Map C type names to the key used to select a SEXP constructor (e.g.
## mkString, ScalarReal). Handles pointer cases specially.
## ------------------------------------------------------------------
sexp_ctor_key_rule(type_name, TRUE) %as%
  {
    "ptr"
  }
sexp_ctor_key_rule("void*", FALSE) %as%
  {
    "ptr"
  }
sexp_ctor_key_rule("void *", FALSE) %as%
  {
    "ptr"
  }
sexp_ctor_key_rule("ptr", FALSE) %as%
  {
    "ptr"
  }
sexp_ctor_key_rule("int", FALSE) %as%
  {
    "int"
  }
sexp_ctor_key_rule("int32_t", FALSE) %as%
  {
    "int"
  }
sexp_ctor_key_rule("i32", FALSE) %as%
  {
    "int"
  }
sexp_ctor_key_rule("int16_t", FALSE) %as%
  {
    "int"
  }
sexp_ctor_key_rule("i16", FALSE) %as%
  {
    "int"
  }
sexp_ctor_key_rule("int8_t", FALSE) %as%
  {
    "int"
  }
sexp_ctor_key_rule("i8", FALSE) %as%
  {
    "int"
  }
sexp_ctor_key_rule("uint8_t", FALSE) %as%
  {
    "int"
  }
sexp_ctor_key_rule("u8", FALSE) %as%
  {
    "int"
  }
sexp_ctor_key_rule("uint16_t", FALSE) %as%
  {
    "int"
  }
sexp_ctor_key_rule("u16", FALSE) %as%
  {
    "int"
  }
sexp_ctor_key_rule("long", FALSE) %as%
  {
    "real"
  }
sexp_ctor_key_rule("long long", FALSE) %as%
  {
    "real"
  }
sexp_ctor_key_rule("int64_t", FALSE) %as%
  {
    "real"
  }
sexp_ctor_key_rule("i64", FALSE) %as%
  {
    "real"
  }
sexp_ctor_key_rule("uint32_t", FALSE) %as%
  {
    "real"
  }
sexp_ctor_key_rule("u32", FALSE) %as%
  {
    "real"
  }
sexp_ctor_key_rule("uint64_t", FALSE) %as%
  {
    "real"
  }
sexp_ctor_key_rule("u64", FALSE) %as%
  {
    "real"
  }
sexp_ctor_key_rule("double", FALSE) %as%
  {
    "real"
  }
sexp_ctor_key_rule("float", FALSE) %as%
  {
    "real"
  }
sexp_ctor_key_rule("f64", FALSE) %as%
  {
    "real"
  }
sexp_ctor_key_rule("f32", FALSE) %as%
  {
    "real"
  }
sexp_ctor_key_rule("char*", FALSE) %as%
  {
    "cstring"
  }
sexp_ctor_key_rule("const char*", FALSE) %as%
  {
    "cstring"
  }
sexp_ctor_key_rule("string", FALSE) %as%
  {
    "cstring"
  }
sexp_ctor_key_rule("cstring", FALSE) %as%
  {
    "cstring"
  }
sexp_ctor_key_rule("bool", FALSE) %as%
  {
    "bool"
  }
sexp_ctor_key_rule("_Bool", FALSE) %as%
  {
    "bool"
  }
sexp_ctor_key_rule("SEXP", FALSE) %as%
  {
    "sexp"
  }
sexp_ctor_key_rule("sexp", FALSE) %as%
  {
    "sexp"
  }
sexp_ctor_key_rule(type_name, is_ptr) %as%
  {
    "ptr"
  }

## ------------------------------------------------------------------
## R -> C key map
##
## Map C type spellings to the key that selects the appropriate R -> C
## converter (e.g. asInteger, asReal, R_ExternalPtrAddr). Pointer types
## map to "ptr".
## ------------------------------------------------------------------
r_to_c_key_rule(type_name, TRUE) %as%
  {
    "ptr"
  }
r_to_c_key_rule("void*", FALSE) %as%
  {
    "ptr"
  }
r_to_c_key_rule("void *", FALSE) %as%
  {
    "ptr"
  }
r_to_c_key_rule("ptr", FALSE) %as%
  {
    "ptr"
  }
r_to_c_key_rule("int", FALSE) %as%
  {
    "int"
  }
r_to_c_key_rule("int32_t", FALSE) %as%
  {
    "int"
  }
r_to_c_key_rule("i32", FALSE) %as%
  {
    "int"
  }
r_to_c_key_rule("int16_t", FALSE) %as%
  {
    "int"
  }
r_to_c_key_rule("i16", FALSE) %as%
  {
    "int"
  }
r_to_c_key_rule("int8_t", FALSE) %as%
  {
    "int"
  }
r_to_c_key_rule("i8", FALSE) %as%
  {
    "int"
  }
r_to_c_key_rule("uint8_t", FALSE) %as%
  {
    "int"
  }
r_to_c_key_rule("u8", FALSE) %as%
  {
    "int"
  }
r_to_c_key_rule("uint16_t", FALSE) %as%
  {
    "int"
  }
r_to_c_key_rule("u16", FALSE) %as%
  {
    "int"
  }
r_to_c_key_rule("long", FALSE) %as%
  {
    "real"
  }
r_to_c_key_rule("long long", FALSE) %as%
  {
    "real"
  }
r_to_c_key_rule("int64_t", FALSE) %as%
  {
    "real"
  }
r_to_c_key_rule("i64", FALSE) %as%
  {
    "real"
  }
r_to_c_key_rule("uint32_t", FALSE) %as%
  {
    "real"
  }
r_to_c_key_rule("u32", FALSE) %as%
  {
    "real"
  }
r_to_c_key_rule("uint64_t", FALSE) %as%
  {
    "real"
  }
r_to_c_key_rule("u64", FALSE) %as%
  {
    "real"
  }
r_to_c_key_rule("double", FALSE) %as%
  {
    "real"
  }
r_to_c_key_rule("float", FALSE) %as%
  {
    "real"
  }
r_to_c_key_rule("f64", FALSE) %as%
  {
    "real"
  }
r_to_c_key_rule("f32", FALSE) %as%
  {
    "real"
  }
r_to_c_key_rule("char*", FALSE) %as%
  {
    "cstring"
  }
r_to_c_key_rule("const char*", FALSE) %as%
  {
    "cstring"
  }
r_to_c_key_rule("string", FALSE) %as%
  {
    "cstring"
  }
r_to_c_key_rule("cstring", FALSE) %as%
  {
    "cstring"
  }
r_to_c_key_rule("bool", FALSE) %as%
  {
    "bool"
  }
r_to_c_key_rule("_Bool", FALSE) %as%
  {
    "bool"
  }
r_to_c_key_rule("SEXP", FALSE) %as%
  {
    "sexp"
  }
r_to_c_key_rule("sexp", FALSE) %as%
  {
    "sexp"
  }
r_to_c_key_rule(type_name, is_ptr) %as%
  {
    "ptr"
  }

## ------------------------------------------------------------------
## Default type key mapping
##
## A general-purpose fallback mapping used when no more specific key
## mapping is appropriate. This helps many rule lookups remain simple.
## ------------------------------------------------------------------
default_key_rule("void", FALSE) %as%
  {
    "void"
  }
default_key_rule("SEXP", FALSE) %as%
  {
    "sexp"
  }
default_key_rule("sexp", FALSE) %as%
  {
    "sexp"
  }
default_key_rule(type_name, TRUE) %as%
  {
    "ptr"
  }
default_key_rule("void*", FALSE) %as%
  {
    "ptr"
  }
default_key_rule("void *", FALSE) %as%
  {
    "ptr"
  }
default_key_rule("ptr", FALSE) %as%
  {
    "ptr"
  }
default_key_rule("char*", FALSE) %as%
  {
    "cstring"
  }
default_key_rule("const char*", FALSE) %as%
  {
    "cstring"
  }
default_key_rule("string", FALSE) %as%
  {
    "cstring"
  }
default_key_rule("cstring", FALSE) %as%
  {
    "cstring"
  }
default_key_rule("double", FALSE) %as%
  {
    "real"
  }
default_key_rule("float", FALSE) %as%
  {
    "real"
  }
default_key_rule("f64", FALSE) %as%
  {
    "real"
  }
default_key_rule("f32", FALSE) %as%
  {
    "real"
  }
default_key_rule("bool", FALSE) %as%
  {
    "logical"
  }
default_key_rule("_Bool", FALSE) %as%
  {
    "logical"
  }
default_key_rule(type_name, is_ptr) %as%
  {
    "int"
  }

## ------------------------------------------------------------------
## SEXP type key mapping
##
## Determine which SEXP type (int/real/longlong/ptr/cstring/etc.) should
## be used for a C type when generating wrappers that will box/unbox
## values to/from R.
## ------------------------------------------------------------------
sexp_type_key_rule(type_name, TRUE) %as%
  {
    "ptr"
  }
sexp_type_key_rule("int", FALSE) %as%
  {
    "int"
  }
sexp_type_key_rule("int32_t", FALSE) %as%
  {
    "int"
  }
sexp_type_key_rule("i32", FALSE) %as%
  {
    "int"
  }
sexp_type_key_rule("int16_t", FALSE) %as%
  {
    "int"
  }
sexp_type_key_rule("i16", FALSE) %as%
  {
    "int"
  }
sexp_type_key_rule("int8_t", FALSE) %as%
  {
    "int"
  }
sexp_type_key_rule("i8", FALSE) %as%
  {
    "int"
  }
sexp_type_key_rule("long", FALSE) %as%
  {
    "longlong"
  }
sexp_type_key_rule("long long", FALSE) %as%
  {
    "longlong"
  }
sexp_type_key_rule("int64_t", FALSE) %as%
  {
    "longlong"
  }
sexp_type_key_rule("i64", FALSE) %as%
  {
    "longlong"
  }
sexp_type_key_rule("uint8_t", FALSE) %as%
  {
    "longlong"
  }
sexp_type_key_rule("u8", FALSE) %as%
  {
    "longlong"
  }
sexp_type_key_rule("uint16_t", FALSE) %as%
  {
    "longlong"
  }
sexp_type_key_rule("u16", FALSE) %as%
  {
    "longlong"
  }
sexp_type_key_rule("uint32_t", FALSE) %as%
  {
    "longlong"
  }
sexp_type_key_rule("u32", FALSE) %as%
  {
    "longlong"
  }
sexp_type_key_rule("uint64_t", FALSE) %as%
  {
    "longlong"
  }
sexp_type_key_rule("u64", FALSE) %as%
  {
    "longlong"
  }
sexp_type_key_rule("double", FALSE) %as%
  {
    "real"
  }
sexp_type_key_rule("float", FALSE) %as%
  {
    "real"
  }
sexp_type_key_rule("f64", FALSE) %as%
  {
    "real"
  }
sexp_type_key_rule("f32", FALSE) %as%
  {
    "real"
  }
sexp_type_key_rule("char*", FALSE) %as%
  {
    "cstring"
  }
sexp_type_key_rule("const char*", FALSE) %as%
  {
    "cstring"
  }
sexp_type_key_rule("string", FALSE) %as%
  {
    "cstring"
  }
sexp_type_key_rule("cstring", FALSE) %as%
  {
    "cstring"
  }
sexp_type_key_rule("void*", FALSE) %as%
  {
    "ptr"
  }
sexp_type_key_rule("void *", FALSE) %as%
  {
    "ptr"
  }
sexp_type_key_rule("ptr", FALSE) %as%
  {
    "ptr"
  }
sexp_type_key_rule("bool", FALSE) %as%
  {
    "bool"
  }
sexp_type_key_rule("_Bool", FALSE) %as%
  {
    "bool"
  }
sexp_type_key_rule("SEXP", FALSE) %as%
  {
    "sexp"
  }
sexp_type_key_rule("sexp", FALSE) %as%
  {
    "sexp"
  }
sexp_type_key_rule(type_name, is_ptr) %as%
  {
    "ptr"
  }

## ------------------------------------------------------------------
## Return type key mapping
##
## Map C return types to the compact keys used by the ffi_return_rule
## lookup (e.g. "i8", "i32", "double", "cstring", "ptr").
## ------------------------------------------------------------------
return_key_rule("void", FALSE) %as%
  {
    "void"
  }
return_key_rule("SEXP", FALSE) %as%
  {
    "sexp"
  }
return_key_rule("sexp", FALSE) %as%
  {
    "sexp"
  }
return_key_rule(type_name, TRUE) %as%
  {
    "ptr"
  }
return_key_rule("void*", FALSE) %as%
  {
    "ptr"
  }
return_key_rule("void *", FALSE) %as%
  {
    "ptr"
  }
return_key_rule("ptr", FALSE) %as%
  {
    "ptr"
  }
return_key_rule("char*", FALSE) %as%
  {
    "cstring"
  }
return_key_rule("const char*", FALSE) %as%
  {
    "cstring"
  }
return_key_rule("string", FALSE) %as%
  {
    "cstring"
  }
return_key_rule("cstring", FALSE) %as%
  {
    "cstring"
  }
return_key_rule("bool", FALSE) %as%
  {
    "bool"
  }
return_key_rule("_Bool", FALSE) %as%
  {
    "bool"
  }
return_key_rule("int8_t", FALSE) %as%
  {
    "i8"
  }
return_key_rule("i8", FALSE) %as%
  {
    "i8"
  }
return_key_rule("int16_t", FALSE) %as%
  {
    "i16"
  }
return_key_rule("i16", FALSE) %as%
  {
    "i16"
  }
return_key_rule("int32_t", FALSE) %as%
  {
    "i32"
  }
return_key_rule("i32", FALSE) %as%
  {
    "i32"
  }
return_key_rule("int", FALSE) %as%
  {
    "int"
  }
return_key_rule("long", FALSE) %as%
  {
    "int"
  }
return_key_rule("short", FALSE) %as%
  {
    "int"
  }
return_key_rule("uint8_t", FALSE) %as%
  {
    "u8"
  }
return_key_rule("u8", FALSE) %as%
  {
    "u8"
  }
return_key_rule("uint16_t", FALSE) %as%
  {
    "u16"
  }
return_key_rule("u16", FALSE) %as%
  {
    "u16"
  }
return_key_rule("uint32_t", FALSE) %as%
  {
    "u32"
  }
return_key_rule("u32", FALSE) %as%
  {
    "u32"
  }
return_key_rule("int64_t", FALSE) %as%
  {
    "i64"
  }
return_key_rule("i64", FALSE) %as%
  {
    "i64"
  }
return_key_rule("long long", FALSE) %as%
  {
    "i64"
  }
return_key_rule("uint64_t", FALSE) %as%
  {
    "u64"
  }
return_key_rule("u64", FALSE) %as%
  {
    "u64"
  }
return_key_rule("double", FALSE) %as%
  {
    "double"
  }
return_key_rule("f64", FALSE) %as%
  {
    "double"
  }
return_key_rule("float", FALSE) %as%
  {
    "float"
  }
return_key_rule("f32", FALSE) %as%
  {
    "float"
  }
return_key_rule(type_name, is_ptr) %as%
  {
    "ptr"
  }

## ------------------------------------------------------------------
## FFI C type canonicalization
##
## Map many C type spellings into the canonical internal FFI type keys
## used throughout this file (i8/i16/i32/i64/u8/u16/u32/u64/f32/f64/ptr
## etc.). This central lookup keeps downstream rule selection uniform.
## ------------------------------------------------------------------
ffi_c_type_map_rule(type_name, TRUE, is_ptr) %as%
  {
    "ptr"
  }
ffi_c_type_map_rule(type_name, FALSE, TRUE) %as%
  {
    "ptr"
  }
ffi_c_type_map_rule("void", FALSE, FALSE) %as%
  {
    "void"
  }
ffi_c_type_map_rule("bool", FALSE, FALSE) %as%
  {
    "bool"
  }
ffi_c_type_map_rule("_Bool", FALSE, FALSE) %as%
  {
    "bool"
  }
ffi_c_type_map_rule("SEXP", FALSE, FALSE) %as%
  {
    "sexp"
  }
ffi_c_type_map_rule("sexp", FALSE, FALSE) %as%
  {
    "sexp"
  }
ffi_c_type_map_rule("int", FALSE, FALSE) %as%
  {
    "i32"
  }
ffi_c_type_map_rule("signed", FALSE, FALSE) %as%
  {
    "i32"
  }
ffi_c_type_map_rule("int32_t", FALSE, FALSE) %as%
  {
    "i32"
  }
ffi_c_type_map_rule("__int32", FALSE, FALSE) %as%
  {
    "i32"
  }
ffi_c_type_map_rule("signed int", FALSE, FALSE) %as%
  {
    "i32"
  }
ffi_c_type_map_rule("short", FALSE, FALSE) %as%
  {
    "i16"
  }
ffi_c_type_map_rule("short int", FALSE, FALSE) %as%
  {
    "i16"
  }
ffi_c_type_map_rule("signed short", FALSE, FALSE) %as%
  {
    "i16"
  }
ffi_c_type_map_rule("signed short int", FALSE, FALSE) %as%
  {
    "i16"
  }
ffi_c_type_map_rule("int16_t", FALSE, FALSE) %as%
  {
    "i16"
  }
ffi_c_type_map_rule("char", FALSE, FALSE) %as%
  {
    "i8"
  }
ffi_c_type_map_rule("signed char", FALSE, FALSE) %as%
  {
    "i8"
  }
ffi_c_type_map_rule("int8_t", FALSE, FALSE) %as%
  {
    "i8"
  }
ffi_c_type_map_rule("long", FALSE, FALSE) %as%
  {
    "i64"
  }
ffi_c_type_map_rule("long int", FALSE, FALSE) %as%
  {
    "i64"
  }
ffi_c_type_map_rule("long long", FALSE, FALSE) %as%
  {
    "i64"
  }
ffi_c_type_map_rule("long long int", FALSE, FALSE) %as%
  {
    "i64"
  }
ffi_c_type_map_rule("signed long", FALSE, FALSE) %as%
  {
    "i64"
  }
ffi_c_type_map_rule("signed long int", FALSE, FALSE) %as%
  {
    "i64"
  }
ffi_c_type_map_rule("signed long long", FALSE, FALSE) %as%
  {
    "i64"
  }
ffi_c_type_map_rule("signed long long int", FALSE, FALSE) %as%
  {
    "i64"
  }
ffi_c_type_map_rule("int64_t", FALSE, FALSE) %as%
  {
    "i64"
  }
ffi_c_type_map_rule("__int64", FALSE, FALSE) %as%
  {
    "i64"
  }
ffi_c_type_map_rule("intptr_t", FALSE, FALSE) %as%
  {
    "i64"
  }
ffi_c_type_map_rule("ptrdiff_t", FALSE, FALSE) %as%
  {
    "i64"
  }
ffi_c_type_map_rule("ssize_t", FALSE, FALSE) %as%
  {
    "i64"
  }
ffi_c_type_map_rule("off_t", FALSE, FALSE) %as%
  {
    "i64"
  }
ffi_c_type_map_rule("unsigned int", FALSE, FALSE) %as%
  {
    "u32"
  }
ffi_c_type_map_rule("unsigned", FALSE, FALSE) %as%
  {
    "u32"
  }
ffi_c_type_map_rule("uint32_t", FALSE, FALSE) %as%
  {
    "u32"
  }
ffi_c_type_map_rule("unsigned __int32", FALSE, FALSE) %as%
  {
    "u32"
  }
ffi_c_type_map_rule("unsigned short", FALSE, FALSE) %as%
  {
    "u16"
  }
ffi_c_type_map_rule("unsigned short int", FALSE, FALSE) %as%
  {
    "u16"
  }
ffi_c_type_map_rule("uint16_t", FALSE, FALSE) %as%
  {
    "u16"
  }
ffi_c_type_map_rule("unsigned char", FALSE, FALSE) %as%
  {
    "u8"
  }
ffi_c_type_map_rule("uint8_t", FALSE, FALSE) %as%
  {
    "u8"
  }
ffi_c_type_map_rule("unsigned long", FALSE, FALSE) %as%
  {
    "u64"
  }
ffi_c_type_map_rule("unsigned long int", FALSE, FALSE) %as%
  {
    "u64"
  }
ffi_c_type_map_rule("unsigned long long", FALSE, FALSE) %as%
  {
    "u64"
  }
ffi_c_type_map_rule("unsigned long long int", FALSE, FALSE) %as%
  {
    "u64"
  }
ffi_c_type_map_rule("uint64_t", FALSE, FALSE) %as%
  {
    "u64"
  }
ffi_c_type_map_rule("unsigned __int64", FALSE, FALSE) %as%
  {
    "u64"
  }
ffi_c_type_map_rule("size_t", FALSE, FALSE) %as%
  {
    "u64"
  }
ffi_c_type_map_rule("uintptr_t", FALSE, FALSE) %as%
  {
    "u64"
  }
ffi_c_type_map_rule("double", FALSE, FALSE) %as%
  {
    "f64"
  }
ffi_c_type_map_rule("long double", FALSE, FALSE) %as%
  {
    "f64"
  }
ffi_c_type_map_rule("float", FALSE, FALSE) %as%
  {
    "f32"
  }
ffi_c_type_map_rule(type_name, is_char_ptr, is_ptr) %as%
  {
    "ptr"
  }