From a007dd5d22570790523c61aaee5782bdbab2f7d3 Mon Sep 17 00:00:00 2001
From: Delyan Angelov <delian66@gmail.com>
Date: Sun, 18 Jul 2021 15:46:02 +0300
Subject: [PATCH] builder: support `-o -` to print the generated C/JS source to
 stdout

---
 cmd/tools/vtest-all.v | 9 ++++++++-
 vlib/v/builder/cc.v   | 7 +++++++
 2 files changed, 15 insertions(+), 1 deletion(-)

diff --git a/cmd/tools/vtest-all.v b/cmd/tools/vtest-all.v
index aaf0164f81..dd6a5bfe50 100644
--- a/cmd/tools/vtest-all.v
+++ b/cmd/tools/vtest-all.v
@@ -62,6 +62,12 @@ fn get_all_commands() []Command {
 		okmsg: 'V can output a .c file, without compiling further.'
 		rmfile: 'hhww.c'
 	}
+	$if linux || macos {
+		res << Command{
+			line: '$vexe -o - examples/hello_world.v | grep "#define V_COMMIT_HASH" > /dev/null'
+			okmsg: 'V prints the generated source code to stdout with `-o -` .'
+		}
+	}
 	res << Command{
 		line: '$vexe -o vtmp cmd/v'
 		okmsg: 'V can compile itself.'
@@ -152,7 +158,8 @@ fn (mut cmd Command) run() {
 	sw := time.new_stopwatch({})
 	cmd.ecode = os.system(cmd.line)
 	spent := sw.elapsed().milliseconds()
-	println(term_highlight('> Running: "$cmd.line" took: $spent ms.'))
+	println('> Running: "$cmd.line" took: $spent ms ... ' +
+		if cmd.ecode != 0 { term.failed('FAILED') } else { term_highlight('OK') })
 	if vtest_nocleanup {
 		return
 	}
diff --git a/vlib/v/builder/cc.v b/vlib/v/builder/cc.v
index ffb8750166..6f867f799a 100644
--- a/vlib/v/builder/cc.v
+++ b/vlib/v/builder/cc.v
@@ -479,6 +479,13 @@ fn (mut v Builder) cc() {
 		}
 		return
 	}
+	if v.pref.out_name.ends_with('/-') {
+		// output to stdout
+		content := os.read_file(v.out_name_c) or { panic(err) }
+		println(content)
+		os.rm(v.out_name_c) or {}
+		return
+	}
 	// whether to just create a .c or .js file and exit, for example: `v -o v.c cmd.v`
 	ends_with_c := v.pref.out_name.ends_with('.c')
 	ends_with_js := v.pref.out_name.ends_with('.js')