zig clean & refactor

Author: kassane

Diff for: examples/hello_zig/Makefile

@@ -25,7 +25,7 @@ include $(APPDIR)/Make.defs
 MAINSRC = hello_zig.zig
 
 # Hello, Zig! built-in application info
-
+ZIGFLAGS += -lc -I$(TOPDIR)/include
 PROGNAME  = $(CONFIG_EXAMPLES_HELLO_ZIG_PROGNAME)
 PRIORITY  = $(CONFIG_EXAMPLES_HELLO_ZIG_PRIORITY)
 STACKSIZE = $(CONFIG_EXAMPLES_HELLO_ZIG_STACKSIZE)

Diff for: examples/hello_zig/hello_zig.zig

@@ -24,17 +24,36 @@
 const std = @import("std");
 
 //****************************************************************************
-//* Externs
+//* C API - need libc linking (freestanding libc is stubs only)
 //****************************************************************************
+// nuttx namespace
+const nuttx = struct {
+    pub const c = @cImport({
+        @cInclude("nuttx/config.h");
+        @cInclude("stdio.h");
+    });
+};
 
-pub extern fn printf(_format: [*:0]const u8) c_int;
+// or (optional) const c = std.c; // from std library (non-full libc)
 
+// typedef alias
+const printf = nuttx.c.printf;
 //****************************************************************************
 //* hello_zig_main
 //****************************************************************************
-pub export fn main(_argc: c_int, _argv: [*]const [*]const u8) u8 {
-    _ = _argc;
-    _ = _argv;
-    _ = printf("Hello, Zig!\n");
+comptime {
+    // rename to hello_zig_main entry point for nuttx
+    @export(hello_zig, .{
+        .name = "hello_zig_main",
+        .linkage = .weak,
+    });
+}
+
+fn hello_zig(_: c_int, _: ?[*]const [*]const u8) callconv(.C) c_int {
+    print("[{s}]: Hello, Zig!\n", .{nuttx.c.CONFIG_ARCH_BOARD});
     return 0;
 }
+
+fn print(comptime fmt: [*:0]const u8, args: anytype) void {
+    _ = printf(std.fmt.comptimePrint(std.mem.span(fmt), args));
+}