builtin: add pub fn arguments() []string {; make os.args use it, remove edge case in cgen

vlib/builtin/builtin.c.v

@@ -711,14 +711,32 @@ fn v_fixed_index(i int, len int) int {
 
 // NOTE: g_main_argc and g_main_argv are filled in right after C's main start.
 // They are used internally by V's builtin; for user code, it is much
-// more convenient to just use `os.args` instead.
+// more convenient to just use `os.args` or call `arguments()` instead.
 
 @[markused]
 __global g_main_argc = int(0)
 
 @[markused]
 __global g_main_argv = unsafe { nil }
 
+// arguments returns the command line arguments, used for starting the current program as a V array of strings.
+// The first string in the array (index 0), is the name of the program, used for invoking the program.
+// The second string in the array (index 1), if it exists, is the first argument to the program, etc.
+// For example, if you started your program as `myprogram -option`, then arguments() will return ['myprogram', '-option'].
+// Note: if you `v run file.v abc def`, then arguments() will return ['file', 'abc', 'def'], or ['file.exe', 'abc', 'def'] (on Windows).
+pub fn arguments() []string {
+	argv := &&u8(g_main_argv)
+	mut res := []string{cap: g_main_argc}
+	for i in 0 .. g_main_argc {
+		$if windows {
+			res << unsafe { string_from_wide(&u16(argv[i])) }
+		} $else {
+			res << unsafe { tos_clone(argv[i]) }
+		}
+	}
+	return res
+}
+
 @[if vplayground ?]
 fn vplayground_mlimit(n isize) {
 	if n > 10000 {

vlib/os/os.c.v

@@ -9,7 +9,7 @@ $if freebsd || openbsd {
 	#include <sys/sysctl.h>
 }
 
-pub const args = []string{}
+pub const args = arguments()
 
 fn C.readdir(voidptr) &C.dirent
 

vlib/os/os_nix.c.v

@@ -272,6 +272,8 @@ pub fn loginname() !string {
 	return error(posix_get_error_msg(C.errno))
 }
 
+@[deprecated: 'os.args now uses arguments()']
+@[deprecated_after: '2024-07-30']
 fn init_os_args(argc int, argv &&u8) []string {
 	mut args_ := []string{len: argc}
 	for i in 0 .. argc {

vlib/os/os_windows.c.v

@@ -103,6 +103,8 @@ pub struct C._utimbuf {
 
 fn C._utime(&char, voidptr) int
 
+@[deprecated: 'os.args now uses arguments()']
+@[deprecated_after: '2024-07-30']
 fn init_os_args_wide(argc int, argv &&u8) []string {
 	mut args_ := []string{len: argc}
 	for i in 0 .. argc {

vlib/v/gen/c/cgen.v

@@ -6116,29 +6116,22 @@ fn (mut g Gen) const_decl_init_later(mod string, name string, expr ast.Expr, typ
 	mut styp := g.typ(typ)
 	cname := g.c_const_name(name)
 	mut init := strings.new_builder(100)
-	if cname == '_const_os__args' {
-		if g.pref.os == .windows {
-			init.writeln('\t_const_os__args = os__init_os_args_wide(___argc, (byteptr*)___argv);')
-		} else {
-			init.writeln('\t_const_os__args = os__init_os_args(___argc, (byte**)___argv);')
-		}
+
+	if surround_cbr {
+		init.writeln('{')
+	}
+	if unwrap_option {
+		init.writeln(g.expr_string_surround('\t${cname} = *(${styp}*)', expr, '.data;'))
+	} else if expr is ast.ArrayInit && (expr as ast.ArrayInit).has_index {
+		init.writeln(g.expr_string_surround('\tmemcpy(&${cname}, &', expr, ', sizeof(${styp}));'))
+	} else if expr is ast.CallExpr
+		&& g.table.final_sym(g.unwrap_generic((expr as ast.CallExpr).return_type)).kind == .array_fixed {
+		init.writeln(g.expr_string_surround('\tmemcpy(&${cname}, ', expr, ', sizeof(${styp}));'))
 	} else {
-		if surround_cbr {
-			init.writeln('{')
-		}
-		if unwrap_option {
-			init.writeln(g.expr_string_surround('\t${cname} = *(${styp}*)', expr, '.data;'))
-		} else if expr is ast.ArrayInit && (expr as ast.ArrayInit).has_index {
-			init.writeln(g.expr_string_surround('\tmemcpy(&${cname}, &', expr, ', sizeof(${styp}));'))
-		} else if expr is ast.CallExpr
-			&& g.table.final_sym(g.unwrap_generic((expr as ast.CallExpr).return_type)).kind == .array_fixed {
-			init.writeln(g.expr_string_surround('\tmemcpy(&${cname}, ', expr, ', sizeof(${styp}));'))
-		} else {
-			init.writeln(g.expr_string_surround('\t${cname} = ', expr, ';'))
-		}
-		if surround_cbr {
-			init.writeln('}')
-		}
+		init.writeln(g.expr_string_surround('\t${cname} = ', expr, ';'))
+	}
+	if surround_cbr {
+		init.writeln('}')
 	}
 	mut def := '${styp} ${cname}'
 	expr_sym := g.table.sym(typ)
@@ -6288,7 +6281,11 @@ fn (mut g Gen) global_decl(node ast.GlobalDecl) {
 			} else {
 				// More complex expressions need to be moved to `_vinit()`
 				// e.g. `__global ( mygblobal = 'hello ' + world' )`
-				init = '\t${field.name} = ${g.expr_string(field.expr)}; // 3global'
+				if field.name in ['g_main_argc', 'g_main_argv'] {
+					init = '\t// skipping ${field.name}, it was initialised in main'
+				} else {
+					init = '\t${field.name} = ${g.expr_string(field.expr)}; // 3global'
+				}
 			}
 		} else if !g.pref.translated { // don't zero globals from C code
 			default_initializer := g.type_default(field.typ)

vlib/v/markused/markused.v

@@ -135,8 +135,6 @@ pub fn mark_used(mut table ast.Table, mut pref_ pref.Preferences, ast_files []&a
 			'main.vtest_new_metainfo',
 			'main.vtest_new_filemetainfo',
 			'os.getwd',
-			'os.init_os_args',
-			'os.init_os_args_wide',
 			'v.embed_file.find_index_entry_by_path',
 		]
 	}

vlib/v/slow_tests/profile/profile_test.v

@@ -67,10 +67,10 @@ fn test_v_profile_works() {
 	println(@FN)
 	sfile := 'vlib/v/slow_tests/profile/profile_test_1.v'
 	validate_output(@FN, '', sfile, {
-		'os__init_os_args': 1
-		'main__main':       1
-		'println':          1
-		'strconv__atoi':    1
+		'arguments':     1
+		'main__main':    1
+		'println':       1
+		'strconv__atoi': 1
 	})
 }
 

vlib/v/tests/testdata/trace_calls/with_modules.vv.must_match

@@ -1,6 +1,6 @@
 *> trace * C.main*
 *> trace * _vinit*
-*> trace * os os.init_os_args*
+*> trace * builtin arguments/0*
 *> trace * main main.main/0*
 *> trace * main main.f1/0*
 *> trace * main main.f2/0*