os, v.builder: show more details, when a program ran by `v run file.v…

…`, exits by a signal (fix #19412) (#19471)

vlib/os/os.c.v

@@ -429,10 +429,11 @@ pub fn system(cmd string) int {
 	}
 	$if !windows {
 		pret, is_signaled := posix_wait4_to_exit_status(ret)
+		ret = pret
 		if is_signaled {
-			println('Terminated by signal ${ret:2d} (' + sigint_to_signal_name(pret) + ')')
+			eprintln('Terminated by signal ${pret:2d} (' + sigint_to_signal_name(pret) + ')')
+			ret = pret + 128
 		}
-		ret = pret
 	}
 	return ret
 }
@@ -541,7 +542,7 @@ pub fn rmdir(path string) ! {
 fn print_c_errno() {
 	e := C.errno
 	se := unsafe { tos_clone(&u8(C.strerror(e))) }
-	println('errno=${e} err=${se}')
+	eprintln('errno=${e} err=${se}')
 }
 
 // get_raw_line returns a one-line string from stdin along with '\n' if there is any.

vlib/os/process_nix.c.v

@@ -83,42 +83,32 @@ fn (mut p Process) unix_kill_pgroup() {
 }
 
 fn (mut p Process) unix_wait() {
-	cstatus := 0
-	mut ret := -1
-	$if !emscripten ? {
-		ret = C.waitpid(p.pid, &cstatus, 0)
-	}
-	if ret == -1 {
-		p.err = posix_get_error_msg(C.errno)
-		return
-	}
-	pret, is_signaled := posix_wait4_to_exit_status(cstatus)
-	if is_signaled {
-		p.status = .aborted
-		p.err = 'Terminated by signal ${ret:2d} (${sigint_to_signal_name(pret)})'
-	} else {
-		p.status = .exited
-	}
-	p.code = pret
+	p.impl_check_pid_status(false, 0)
 }
 
 fn (mut p Process) unix_is_alive() bool {
-	cstatus := 0
+	return p.impl_check_pid_status(true, C.WNOHANG)
+}
+
+fn (mut p Process) impl_check_pid_status(exit_early_on_ret0 bool, waitpid_options int) bool {
+	mut cstatus := 0
 	mut ret := -1
 	$if !emscripten ? {
-		ret = C.waitpid(p.pid, &cstatus, C.WNOHANG)
+		ret = C.waitpid(p.pid, &cstatus, waitpid_options)
 	}
+	p.code = ret
 	if ret == -1 {
 		p.err = posix_get_error_msg(C.errno)
 		return false
 	}
-	if ret == 0 {
+	if exit_early_on_ret0 && ret == 0 {
 		return true
 	}
-	pret, is_signaled := posix_wait4_to_exit_status(cstatus)
+	mut pret, is_signaled := posix_wait4_to_exit_status(cstatus)
 	if is_signaled {
 		p.status = .aborted
-		p.err = 'Terminated by signal ${ret:2d} (${sigint_to_signal_name(pret)})'
+		p.err = 'Terminated by signal ${pret:2d} (${sigint_to_signal_name(pret)})'
+		pret += 128
 	} else {
 		p.status = .exited
 	}

vlib/v/builder/compile.v

@@ -160,6 +160,9 @@ fn (mut b Builder) run_compiled_executable_and_exit() {
 			os.signal_opt(.quit, prev_quit_handler) or { serror('restore .quit', err) }
 		}
 		ret = run_process.code
+		if run_process.err != '' {
+			eprintln(run_process.err)
+		}
 		run_process.close()
 	}
 	b.cleanup_run_executable_after_exit(compiled_file)