From c2ce06eba7627c7e3ed6d48ecb8a5f7148e25630 Mon Sep 17 00:00:00 2001
From: Alexander Medvednikov <alexander@medvednikov.com>
Date: Sun, 22 Mar 2020 13:55:39 +0100
Subject: [PATCH] cgen: generate #ifdefs

---
 vlib/v/ast/ast.v         |  3 +-
 vlib/v/checker/checker.v |  2 +-
 vlib/v/gen/cgen.v        | 68 ++++++++++++++++++++++++++++++++++++++--
 vlib/v/parser/comptime.v |  3 +-
 4 files changed, 70 insertions(+), 6 deletions(-)

diff --git a/vlib/v/ast/ast.v b/vlib/v/ast/ast.v
index 6189187216..1d9dbd9813 100644
--- a/vlib/v/ast/ast.v
+++ b/vlib/v/ast/ast.v
@@ -386,7 +386,8 @@ pub:
 
 pub struct CompIf {
 pub:
-	cond       Expr
+// cond       Expr
+	val        string
 	stmts      []Stmt
 	pos        token.Position
 mut:
diff --git a/vlib/v/checker/checker.v b/vlib/v/checker/checker.v
index 954d08476c..50af39b4fd 100644
--- a/vlib/v/checker/checker.v
+++ b/vlib/v/checker/checker.v
@@ -530,7 +530,7 @@ fn (c mut Checker) stmt(node ast.Stmt) {
 		}
 		// ast.Attr {}
 		ast.CompIf {
-			c.expr(it.cond)
+			// c.expr(it.cond)
 			c.stmts(it.stmts)
 		}
 		ast.ConstDecl {
diff --git a/vlib/v/gen/cgen.v b/vlib/v/gen/cgen.v
index b66efc1129..3e80003941 100644
--- a/vlib/v/gen/cgen.v
+++ b/vlib/v/gen/cgen.v
@@ -268,12 +268,13 @@ fn (g mut Gen) stmt(node ast.Stmt) {
 			g.const_decl(it)
 		}
 		ast.CompIf {
-			g.writeln('//#ifdef ')
-			g.expr(it.cond)
+			g.writeln('\n#ifdef ' + comp_if_to_ifdef(it.val))
+			g.writeln('// #if $it.val')
+			// g.expr(it.cond)
 			// println('comp if stmts $g.file.path:$it.pos.line_nr')
 			g.stmts(it.stmts)
 			// println('done')
-			g.writeln('//#endif')
+			g.writeln('#endif')
 		}
 		ast.DeferStmt {
 			g.writeln('// defer')
@@ -1965,3 +1966,64 @@ fn op_to_fn_name(name string) string {
 			'bad op $name'}
 	}
 }
+
+fn comp_if_to_ifdef(name string) string {
+	match name {
+		'windows' {
+			return '_WIN32'
+		}
+		'mac' {
+			return '__APPLE__'
+		}
+		'macos' {
+			return '__APPLE__'
+		}
+		'linux' {
+			return '__linux__'
+		}
+		'freebsd' {
+			return '__FreeBSD__'
+		}
+		'openbsd' {
+			return '__OpenBSD__'
+		}
+		'netbsd' {
+			return '__NetBSD__'
+		}
+		'dragonfly' {
+			return '__DragonFly__'
+		}
+		'msvc' {
+			return '_MSC_VER'
+		}
+		'android' {
+			return '__ANDROID__'
+		}
+		'js' {
+			return '_VJS'
+		}
+		'solaris' {
+			return '__sun'
+		}
+		'haiku' {
+			return '__haiku__'
+		}
+		'tinyc' {
+			return 'tinyc'
+		}
+		'debug' {
+			return '_VDEBUG'
+		}
+		'linux_or_macos' {
+			return ''
+		}
+		'no_bounds_checking' {
+			return 'NO_BOUNDS_CHECK'
+		}
+		else {
+			verror('bad os ifdef name "$name"')
+		}
+	}
+	// verror('bad os ifdef name "$name"')
+	return ''
+}
diff --git a/vlib/v/parser/comptime.v b/vlib/v/parser/comptime.v
index 5b1ed3c71e..78af8a4353 100644
--- a/vlib/v/parser/comptime.v
+++ b/vlib/v/parser/comptime.v
@@ -11,13 +11,14 @@ pub fn (p mut Parser) comp_if() ast.CompIf {
 	if p.tok.kind == .not {
 		p.next()
 	}
-	p.check_name()
+	val := p.check_name()
 	if p.tok.kind == .question {
 		p.next()
 	}
 	mut node := ast.CompIf{
 		stmts: p.parse_block()
 		pos: pos
+		val: val
 	}
 	if p.tok.kind == .dollar && p.peek_tok.kind == .key_else {
 		p.next()