From: Russ Cox <rsc@golang.org>
Date: Fri, 1 Feb 2013 16:33:52 +0000 (-0800)
Subject: cmd/cgo: document //export preamble restriction
X-Git-Tag: go1.1rc2~1201
X-Git-Url: http://www.git.cypherpunks.su/?a=commitdiff_plain;h=ed9fc7531d80d0894d52c96a4a79968842df945b;p=gostls13.git

cmd/cgo: document //export preamble restriction

Fixes #3497.

R=golang-dev, iant
CC=golang-dev
https://golang.org/cl/7235075
---

diff --git a/src/cmd/cgo/doc.go b/src/cmd/cgo/doc.go
index 6f3343de54..2618832101 100644
--- a/src/cmd/cgo/doc.go
+++ b/src/cmd/cgo/doc.go
@@ -116,6 +116,11 @@ copied from the cgo input files. Functions with multiple
 return values are mapped to functions returning a struct.
 Not all Go types can be mapped to C types in a useful way.
 
+Using //export in a file places a restriction on the preamble:
+since it is copied into two different C output files, it must not
+contain any definitions, only declarations. Definitions must be
+placed in preambles in other files, or in C source files.
+
 Cgo transforms the input file into four output files: two Go source
 files, a C file for 6c (or 8c or 5c), and a C file for gcc.