From 9e26c4bd1a948bf61866fc483f14ad930b1b1dcf Mon Sep 17 00:00:00 2001
From: Russ Cox <rsc@golang.org>
Date: Mon, 13 Dec 2010 15:34:45 -0500
Subject: [PATCH] gc: complex(0)

Fixes #1232.

R=ken2
CC=golang-dev
https://golang.org/cl/3621041
---
 src/cmd/gc/const.c    | 8 +++-----
 src/cmd/gc/mparith1.c | 2 ++
 test/cmplx.go         | 1 +
 3 files changed, 6 insertions(+), 5 deletions(-)

diff --git a/src/cmd/gc/const.c b/src/cmd/gc/const.c
index 5a7c5489428..72e67a63405 100644
--- a/src/cmd/gc/const.c
+++ b/src/cmd/gc/const.c
@@ -202,8 +202,6 @@ convlit1(Node **np, Type *t, int explicit)
 				goto bad;
 			case CTFLT:
 			case CTINT:
-				if(explicit)
-					goto bad;
 				n->val = tocplx(n->val);
 				break;
 			case CTCPLX:
@@ -300,7 +298,7 @@ toflt(Val v)
 		f = mal(sizeof(*f));
 		mpmovefltflt(f, &v.u.cval->real);
 		if(mpcmpfltc(&v.u.cval->imag, 0) != 0)
-			yyerror("constant %#F truncated to real", v.u.fval);
+			yyerror("constant %#F%+#Fi truncated to real", &v.u.cval->real, &v.u.cval->imag);
 		v.ctype = CTFLT;
 		v.u.fval = f;
 		break;
@@ -324,9 +322,9 @@ toint(Val v)
 	case CTCPLX:
 		i = mal(sizeof(*i));
 		if(mpmovefltfix(i, &v.u.cval->real) < 0)
-			yyerror("constant %#F truncated to integer", v.u.fval);
+			yyerror("constant %#F%+#Fi truncated to integer", &v.u.cval->real, &v.u.cval->imag);
 		if(mpcmpfltc(&v.u.cval->imag, 0) != 0)
-			yyerror("constant %#F truncated to real", v.u.fval);
+			yyerror("constant %#F%+#Fi truncated to real", &v.u.cval->real, &v.u.cval->imag);
 		v.ctype = CTINT;
 		v.u.xval = i;
 		break;
diff --git a/src/cmd/gc/mparith1.c b/src/cmd/gc/mparith1.c
index fa0103ea0cb..6cd4e25000a 100644
--- a/src/cmd/gc/mparith1.c
+++ b/src/cmd/gc/mparith1.c
@@ -475,6 +475,8 @@ Fconv(Fmt *fp)
 		// for well in range, convert to double and use print's %g
 		if(-900 < fvp->exp && fvp->exp < 900) {
 			d = mpgetflt(fvp);
+			if(d >= 0 && (fp->flags & FmtSign))
+				fmtprint(fp, "+");
 			return fmtprint(fp, "%g", d);
 		}
 		// TODO(rsc): for well out of range, print
diff --git a/test/cmplx.go b/test/cmplx.go
index 6262c682d0b..fad96c60589 100644
--- a/test/cmplx.go
+++ b/test/cmplx.go
@@ -22,6 +22,7 @@ func main() {
 	c64 = cmplx(f32, f32)
 	c128 = cmplx(f64, f64)
 
+	_ = complex(0) // ok
 	_ = cmplx(f, f32)	// ERROR "cmplx"
 	_ = cmplx(f, f64)	// ERROR "cmplx"
 	_ = cmplx(f32, f)	// ERROR "cmplx"