Declare a global variable getter — tcc

Register a global C symbol so the compiled object exposes getter/setter functions global_<name>_get() and global_<name>_set().

Usage

tcc_global(ffi, name, type)

Arguments

ffi: A tcc_ffi object
name: Global symbol name
type: FFI type for the global (scalar types only)

Value

Updated tcc_ffi object (for chaining)

Details

Globals are limited to scalar FFI types. Array types are rejected. Scalar conversions follow the same rules as wrapper arguments:

Integer inputs (i8, i16, i32, u8, u16) must be finite and within range; NA values error.
Large integer types (i64, u32, u64) are mediated through R numeric (double). Values must be integer-valued and within range; for i64/u64 only exact integers up to $2^53$ are accepted.
Getter wrappers for i64/u64 warn when the stored value exceeds R's exact integer range for numeric vectors.
bool rejects NA logicals.

Ownership notes:

ptr globals store the raw address from an external pointer. If the external pointer owns memory, keep it alive; otherwise the pointer may be freed while the global still points to it.
cstring globals are rejected because a global would outlive the borrowed R string view. Declare the global as ptr and manage its storage explicitly with an owned object such as tcc_cstring().

Note

Global helpers are generated inside the compiled TCC unit. Recompiling creates a new instance of the global variable; existing compiled objects continue to refer to their own copy.

Examples

ffi <- tcc_ffi() |>
  tcc_source("int global_counter = 7;") |>
  tcc_global("global_counter", "i32") |>
  tcc_compile()
ffi$global_global_counter_get()
#> [1] 7