show an info message if a C compiler is not installed

0.2_roadmap.txt

@@ -38,11 +38,10 @@
 - declarative ui with hot reload (similar to swiftui)
 - "building a simple blog with vweb" tutorial + youtube video
 + fix interfaces
-- merge v.c and v_win.c
 + fast.vlang.io
 + bare metal support
 + inline assembly
 + x64 machine code generation (ELF)
-- require explicit C.fn definitions, add all missing definitions
++ require explicit C.fn definitions, add all missing definitions
 
 

examples/x64/hello_world.v

@@ -1,11 +1,14 @@
+fn test_fn() {
+	println('test fn')
+}	
+
 fn main() {
 	println('x64 test')
 	for _ in 0..5 {
 		println('Hello world from V x64 machine code generator!')
 	}
 	println('Hello again!')
+	test_fn()
+	println('dne')
 }
 
-fn test_fn() {
-	println('test fn')
-}	

vlib/compiler/cc.v

@@ -311,12 +311,14 @@ start:
 					goto start
 				}
 			}
+
 			verror('C compiler error, while attempting to run: \n' +
 				'-----------------------------------------------------------\n' +
 				'$cmd\n' +
 				'-----------------------------------------------------------\n' +
 				'Probably your C compiler is missing. \n' +
-				'Please reinstall it, or make it available in your PATH.')
+				'Please reinstall it, or make it available in your PATH.\n\n' +
+				missing_compiler_info())
 		}
 
 		if v.pref.is_debug {
@@ -512,3 +514,16 @@ fn get_cmdline_cflags(args []string) string {
 	}
 	return cflags
 }
+
+fn missing_compiler_info() string {
+	$if windows {
+		return 'https://github.com/vlang/v/wiki/Installing-a-C-compiler-on-Windows'
+	}
+	$if linux {
+		return 'On Debian/Ubuntu, run `sudo apt install build-essential`'
+	}
+	$if mac {
+		return 'Install command line XCode tools with `xcode-select --install`'
+	}
+	return ''
+}

vlib/compiler/fn.v

@@ -512,6 +512,9 @@ fn (p mut Parser) fn_decl() {
 			f.defer_text[f.scope_level] = '  ${cgen_name}_time += time__ticks() - _PROF_START;'
 		}
 	}
+	if p.pref.x64 {
+		p.x64.register_function_address(f.name)
+	}	
 	p.statements_no_rcbr()
 	//p.cgen.nogen = false
 	// Print counting result after all statements in main
@@ -712,6 +715,9 @@ fn (p mut Parser) fn_call(f mut Fn, method_ph int, receiver_var, receiver_type s
 	if is_comptime_define {
 		p.cgen.nogen = true
 	}
+	if p.pref.x64 && !p.first_pass() {
+		p.x64.call_fn(f.name)
+	}	
 	p.calling_c = f.is_c
 	if f.is_c && !p.builtin_mod {
 		if f.name == 'free' {

vlib/compiler/x64/gen.v

@@ -15,6 +15,7 @@ mut:
 	file_size_pos i64
 	main_fn_addr i64
 	code_start_pos i64 // location of the start of the assembly instructions
+	fn_addr map[string]i64
 	//string_addr map[string]i64
 }	
 
@@ -44,6 +45,10 @@ pub fn new_gen(out_name string) &Gen {
 	}	
 }	
 
+pub fn (g &Gen) pos() i64 {
+	return g.buf.len
+}	
+
 
 fn (g mut Gen) write8(n int) {
 	// write 1 byte
@@ -155,10 +160,13 @@ fn (g mut Gen) mov64(reg Register, val i64) {
 	g.write64(val)
 }
 
-fn (g mut Gen) call(val int) {
-	//println('call val=$val')
+fn (g mut Gen) call(addr int) {
+	//rel := g.abs_to_rel_addr(addr)
+	rel := 0xffffffff - int(abs(addr - g.buf.len))-1
+	
+	println('call addr=$addr rel_addr=$addr pos=$g.buf.len')
 	g.write8(0xe8)
-	g.write32(val)
+	g.write32(addr)
 }
 
 fn (g mut Gen) syscall() {
@@ -228,4 +236,19 @@ fn (g mut Gen) mov(reg Register, val int) {
 	g.write32(val)
 }
 
+pub fn (g mut Gen) register_function_address(name string) {
+	addr := g.pos()
+	println('reg fn addr $name $addr')
+	g.fn_addr[name] = addr
+}
+
+pub fn (g mut Gen) call_fn(name string) {
+	if !name.contains('__') {
+		return
+	}	
+	addr := g.fn_addr[name]
+	g.call(int(addr))
+	println('call $name $addr')
+}
+