v: add support for iOS crosscompilation (#5943)

cmd/v/help/build-c.txt

@@ -49,8 +49,8 @@ These build flags are enabled on `build` and `run` as long as the backend is set
       Change the target OS that V tries to compile for.
       By default, the target OS is the host system.
       When OS is `cross`, V will attempt to output cross-platform C code.
-      List of OS supported by V: `linux`, `windows`, `mac`, `freebsd`, `openbsd`, `netbsd`,
-                                 `dragonfly`, `solaris`, `android` and `haiku`.
+      List of OS supported by V: `linux`, `windows`, `ios`, `mac`, `freebsd`, `openbsd`,
+                                 `netbsd`, `dragonfly`, `solaris`, `android` and `haiku`.
 
    -sanitize
       Pass flags related to sanitization to the C compiler.

vlib/builtin/cfns.c.v

@@ -67,10 +67,8 @@ fn C.fclose() int
 
 fn C.pclose() int
 
-
 fn C.system() int
 
-
 fn C.setenv(charptr) int
 
 

vlib/os/os.v

@@ -453,9 +453,22 @@ pub fn system(cmd string) int {
 			ret = C._wsystem(wcmd.to_wide())
 		}
 	} $else {
-		unsafe {
-			ret = C.system(charptr(cmd.str))
+/*
+		// make
+		// make selfcompile
+		// ./v -os ios hello.v
+		$if ios {
+			// TODO: use dlsym, use posix_spawn or embed ios_system
+			eprintln('system not supported on ios')
+			ret = 1
+		} $else {
+*/
+			unsafe {
+				ret = C.system(charptr(cmd.str))
+			}
+/*
 		}
+*/
 	}
 	if ret == -1 {
 		print_c_errno()

vlib/v/builder/cc.v

@@ -136,6 +136,9 @@ fn (mut v Builder) cc() {
 			return
 		}
 	}
+	if v.pref.os == .ios {
+		ccompiler = 'xcrun --sdk iphoneos gcc -arch arm64'
+	}
 	// arguments for the C compiler
 	// TODO : activate -Werror once no warnings remain
 	// '-Werror',
@@ -339,6 +342,9 @@ fn (mut v Builder) cc() {
 	if v.pref.os == .mac {
 		a << '-mmacosx-version-min=10.7'
 	}
+	if v.pref.os == .ios {
+		a << '-miphoneos-version-min=10.0'
+	}
 	if v.pref.os == .windows {
 		a << '-municode'
 	}

vlib/v/gen/cgen.v

@@ -253,6 +253,9 @@ pub fn (mut g Gen) init() {
 		g.definitions.writeln('string _STR(const char*, int, ...);')
 		g.definitions.writeln('string _STR_TMP(const char*, ...);')
 	}
+	if g.pref.os == .ios {
+		g.cheaders.writeln('#define __TARGET_IOS__ 1')
+	}
 	g.write_builtin_types()
 	g.write_typedef_types()
 	g.write_typeof_functions()
@@ -3901,6 +3904,9 @@ fn (mut g Gen) comp_if_to_ifdef(name string, is_comptime_optional bool) string {
 		'windows' {
 			return '_WIN32'
 		}
+		'ios' {
+			return '__TARGET_IOS__'
+		}
 		'mac' {
 			return '__APPLE__'
 		}

vlib/v/parser/comptime.v

@@ -28,7 +28,7 @@ fn (mut p Parser) resolve_vroot(flag string) string {
 	vmod_path := vmod_file_location.vmod_folder
 	if p.pref.is_fmt {
 		return flag
-	}        
+	}
 	return flag.replace('@VROOT', os.real_path(vmod_path))
 }
 
@@ -271,6 +271,9 @@ fn os_from_string(os string) pref.OS {
 		'windows' {
 			return .windows
 		}
+		'ios' {
+			return .ios
+		}
 		'mac' {
 			return .mac
 		}

vlib/v/pref/os.v

@@ -5,6 +5,7 @@ module pref
 
 pub enum OS {
 	_auto // Reserved so .mac cannot be misunderstood as auto
+	ios
 	mac
 	linux
 	windows
@@ -27,6 +28,9 @@ pub fn os_from_string(os_str string) ?OS {
 		'windows' {
 			return .windows
 		}
+		'ios' {
+			return .ios
+		}
 		'mac' {
 			return .mac
 		}
@@ -74,6 +78,9 @@ pub fn (o OS) str() string {
 		._auto {
 			return 'RESERVED: AUTO'
 		}
+		.ios {
+			return 'iOS'
+		}
 		.mac {
 			return 'MacOS'
 		}
@@ -114,6 +121,11 @@ pub fn get_host_os() OS {
 	$if linux {
 		return .linux
 	}
+/*
+	$if ios {
+		return .ios
+	}
+*/
 	$if macos {
 		return .mac
 	}

vlib/v/pref/pref.v

@@ -339,7 +339,7 @@ fn must_exist(path string) {
 	if !os.exists(path) {
 		eprintln('v expects that `$path` exists, but it does not')
 		exit(1)
-	}        
+	}
 }
 
 pub fn backend_from_string(s string) ?Backend {