//! Host FFI dispatch for the IR interpreter. //! //! When the interpreter encounters a call to an extern function during `#run` //! (or post-link interpretation), it has no body to walk. This module //! `dlsym`s the symbol from the host's already-loaded dylibs (libc, libSystem, //! kernel32, whatever the OS provides) and calls it via an arity-switched //! cdecl function pointer. //! //! Limits: //! * Up to 8 cdecl-passed arguments. Beyond that, return error. //! * All arguments are marshalled to / from `usize`. Pointer-sized integers, //! pointers, null-terminated strings, and booleans are supported; floats, //! aggregates passed by value, and varargs are not. //! * Return value can be void, integer (i64), pointer (usize), or boolean. const std = @import("std"); const RTLD_DEFAULT: ?*anyopaque = @ptrFromInt(@as(usize, @bitCast(@as(isize, -2)))); extern "c" fn dlsym(handle: ?*anyopaque, name: [*:0]const u8) ?*anyopaque; /// Look up an extern symbol in the host's loaded image. Returns null if not /// found. pub fn lookupSymbol(allocator: std.mem.Allocator, name: []const u8) !?*anyopaque { const name_z = try allocator.allocSentinel(u8, name.len, 0); defer allocator.free(name_z); @memcpy(name_z[0..name.len], name); return dlsym(RTLD_DEFAULT, name_z.ptr); } /// Call a cdecl symbol that returns `i64`. Args are pre-marshalled to `usize`. pub fn callIntRet(symbol: *anyopaque, args: []const usize) !i64 { return switch (args.len) { 0 => @as(*const fn () callconv(.c) i64, @ptrCast(@alignCast(symbol)))(), 1 => @as(*const fn (usize) callconv(.c) i64, @ptrCast(@alignCast(symbol)))(args[0]), 2 => @as(*const fn (usize, usize) callconv(.c) i64, @ptrCast(@alignCast(symbol)))(args[0], args[1]), 3 => @as(*const fn (usize, usize, usize) callconv(.c) i64, @ptrCast(@alignCast(symbol)))(args[0], args[1], args[2]), 4 => @as(*const fn (usize, usize, usize, usize) callconv(.c) i64, @ptrCast(@alignCast(symbol)))(args[0], args[1], args[2], args[3]), 5 => @as(*const fn (usize, usize, usize, usize, usize) callconv(.c) i64, @ptrCast(@alignCast(symbol)))(args[0], args[1], args[2], args[3], args[4]), 6 => @as(*const fn (usize, usize, usize, usize, usize, usize) callconv(.c) i64, @ptrCast(@alignCast(symbol)))(args[0], args[1], args[2], args[3], args[4], args[5]), 7 => @as(*const fn (usize, usize, usize, usize, usize, usize, usize) callconv(.c) i64, @ptrCast(@alignCast(symbol)))(args[0], args[1], args[2], args[3], args[4], args[5], args[6]), 8 => @as(*const fn (usize, usize, usize, usize, usize, usize, usize, usize) callconv(.c) i64, @ptrCast(@alignCast(symbol)))(args[0], args[1], args[2], args[3], args[4], args[5], args[6], args[7]), else => return error.TooManyArgs, }; } /// Call a cdecl symbol that returns a pointer (or any pointer-sized value). pub fn callPtrRet(symbol: *anyopaque, args: []const usize) !usize { return switch (args.len) { 0 => @as(*const fn () callconv(.c) usize, @ptrCast(@alignCast(symbol)))(), 1 => @as(*const fn (usize) callconv(.c) usize, @ptrCast(@alignCast(symbol)))(args[0]), 2 => @as(*const fn (usize, usize) callconv(.c) usize, @ptrCast(@alignCast(symbol)))(args[0], args[1]), 3 => @as(*const fn (usize, usize, usize) callconv(.c) usize, @ptrCast(@alignCast(symbol)))(args[0], args[1], args[2]), 4 => @as(*const fn (usize, usize, usize, usize) callconv(.c) usize, @ptrCast(@alignCast(symbol)))(args[0], args[1], args[2], args[3]), 5 => @as(*const fn (usize, usize, usize, usize, usize) callconv(.c) usize, @ptrCast(@alignCast(symbol)))(args[0], args[1], args[2], args[3], args[4]), 6 => @as(*const fn (usize, usize, usize, usize, usize, usize) callconv(.c) usize, @ptrCast(@alignCast(symbol)))(args[0], args[1], args[2], args[3], args[4], args[5]), 7 => @as(*const fn (usize, usize, usize, usize, usize, usize, usize) callconv(.c) usize, @ptrCast(@alignCast(symbol)))(args[0], args[1], args[2], args[3], args[4], args[5], args[6]), 8 => @as(*const fn (usize, usize, usize, usize, usize, usize, usize, usize) callconv(.c) usize, @ptrCast(@alignCast(symbol)))(args[0], args[1], args[2], args[3], args[4], args[5], args[6], args[7]), else => return error.TooManyArgs, }; } /// Call a cdecl symbol with void return. pub fn callVoidRet(symbol: *anyopaque, args: []const usize) !void { switch (args.len) { 0 => @as(*const fn () callconv(.c) void, @ptrCast(@alignCast(symbol)))(), 1 => @as(*const fn (usize) callconv(.c) void, @ptrCast(@alignCast(symbol)))(args[0]), 2 => @as(*const fn (usize, usize) callconv(.c) void, @ptrCast(@alignCast(symbol)))(args[0], args[1]), 3 => @as(*const fn (usize, usize, usize) callconv(.c) void, @ptrCast(@alignCast(symbol)))(args[0], args[1], args[2]), 4 => @as(*const fn (usize, usize, usize, usize) callconv(.c) void, @ptrCast(@alignCast(symbol)))(args[0], args[1], args[2], args[3]), 5 => @as(*const fn (usize, usize, usize, usize, usize) callconv(.c) void, @ptrCast(@alignCast(symbol)))(args[0], args[1], args[2], args[3], args[4]), 6 => @as(*const fn (usize, usize, usize, usize, usize, usize) callconv(.c) void, @ptrCast(@alignCast(symbol)))(args[0], args[1], args[2], args[3], args[4], args[5]), 7 => @as(*const fn (usize, usize, usize, usize, usize, usize, usize) callconv(.c) void, @ptrCast(@alignCast(symbol)))(args[0], args[1], args[2], args[3], args[4], args[5], args[6]), 8 => @as(*const fn (usize, usize, usize, usize, usize, usize, usize, usize) callconv(.c) void, @ptrCast(@alignCast(symbol)))(args[0], args[1], args[2], args[3], args[4], args[5], args[6], args[7]), else => return error.TooManyArgs, } } // ── Variadic cdecl dispatch ───────────────────────────────────────── // For foreign functions declared with `args: ..T` (C-variadic, e.g. // libc `open(path, flags, ...)`). The trailing args must be passed // through the C-variadic ABI — arm64 places them on the stack rather // than in argument registers. Calling a variadic function as if it // were fixed-arity puts the mode/etc. in the wrong register and the // callee reads garbage. // // The dispatch is keyed by (fixed_count, total_args). `fixed_count` // is the number of declared (non-variadic) params; trailing // `total_args - fixed_count` slots are the variadic tail. The Zig // function-pointer types use `...` so the compiler emits // proper-variadic calls. pub fn callIntRetVar(symbol: *anyopaque, fixed: usize, args: []const usize) !i64 { if (args.len < fixed) return error.TooFewArgs; // Special-case the shapes we actually use today; extend as // needed. fixed_count > total is impossible. return switch (fixed) { 2 => switch (args.len) { 2 => @as(*const fn (usize, usize, ...) callconv(.c) i64, @ptrCast(@alignCast(symbol)))(args[0], args[1]), 3 => @as(*const fn (usize, usize, ...) callconv(.c) i64, @ptrCast(@alignCast(symbol)))(args[0], args[1], args[2]), 4 => @as(*const fn (usize, usize, ...) callconv(.c) i64, @ptrCast(@alignCast(symbol)))(args[0], args[1], args[2], args[3]), 5 => @as(*const fn (usize, usize, ...) callconv(.c) i64, @ptrCast(@alignCast(symbol)))(args[0], args[1], args[2], args[3], args[4]), else => return error.TooManyArgs, }, 1 => switch (args.len) { 1 => @as(*const fn (usize, ...) callconv(.c) i64, @ptrCast(@alignCast(symbol)))(args[0]), 2 => @as(*const fn (usize, ...) callconv(.c) i64, @ptrCast(@alignCast(symbol)))(args[0], args[1]), 3 => @as(*const fn (usize, ...) callconv(.c) i64, @ptrCast(@alignCast(symbol)))(args[0], args[1], args[2]), 4 => @as(*const fn (usize, ...) callconv(.c) i64, @ptrCast(@alignCast(symbol)))(args[0], args[1], args[2], args[3]), 5 => @as(*const fn (usize, ...) callconv(.c) i64, @ptrCast(@alignCast(symbol)))(args[0], args[1], args[2], args[3], args[4]), else => return error.TooManyArgs, }, else => return error.UnsupportedVariadicArity, }; } pub fn callPtrRetVar(symbol: *anyopaque, fixed: usize, args: []const usize) !usize { if (args.len < fixed) return error.TooFewArgs; return switch (fixed) { 2 => switch (args.len) { 2 => @as(*const fn (usize, usize, ...) callconv(.c) usize, @ptrCast(@alignCast(symbol)))(args[0], args[1]), 3 => @as(*const fn (usize, usize, ...) callconv(.c) usize, @ptrCast(@alignCast(symbol)))(args[0], args[1], args[2]), 4 => @as(*const fn (usize, usize, ...) callconv(.c) usize, @ptrCast(@alignCast(symbol)))(args[0], args[1], args[2], args[3]), else => return error.TooManyArgs, }, 1 => switch (args.len) { 1 => @as(*const fn (usize, ...) callconv(.c) usize, @ptrCast(@alignCast(symbol)))(args[0]), 2 => @as(*const fn (usize, ...) callconv(.c) usize, @ptrCast(@alignCast(symbol)))(args[0], args[1]), 3 => @as(*const fn (usize, ...) callconv(.c) usize, @ptrCast(@alignCast(symbol)))(args[0], args[1], args[2]), 4 => @as(*const fn (usize, ...) callconv(.c) usize, @ptrCast(@alignCast(symbol)))(args[0], args[1], args[2], args[3]), else => return error.TooManyArgs, }, else => return error.UnsupportedVariadicArity, }; } pub fn callVoidRetVar(symbol: *anyopaque, fixed: usize, args: []const usize) !void { if (args.len < fixed) return error.TooFewArgs; switch (fixed) { 2 => switch (args.len) { 2 => @as(*const fn (usize, usize, ...) callconv(.c) void, @ptrCast(@alignCast(symbol)))(args[0], args[1]), 3 => @as(*const fn (usize, usize, ...) callconv(.c) void, @ptrCast(@alignCast(symbol)))(args[0], args[1], args[2]), 4 => @as(*const fn (usize, usize, ...) callconv(.c) void, @ptrCast(@alignCast(symbol)))(args[0], args[1], args[2], args[3]), else => return error.TooManyArgs, }, 1 => switch (args.len) { 1 => @as(*const fn (usize, ...) callconv(.c) void, @ptrCast(@alignCast(symbol)))(args[0]), 2 => @as(*const fn (usize, ...) callconv(.c) void, @ptrCast(@alignCast(symbol)))(args[0], args[1]), 3 => @as(*const fn (usize, ...) callconv(.c) void, @ptrCast(@alignCast(symbol)))(args[0], args[1], args[2]), 4 => @as(*const fn (usize, ...) callconv(.c) void, @ptrCast(@alignCast(symbol)))(args[0], args[1], args[2], args[3]), else => return error.TooManyArgs, }, else => return error.UnsupportedVariadicArity, } }