libgo: update to Go1.10rc2

    
    Reviewed-on: https://go-review.googlesource.com/92736

From-SVN: r257493

1 files changed, 13 insertions, 3 deletions

diff --git a/libgo/go/cmd/cgo/doc.go b/libgo/go/cmd/cgo/doc.go
index 8e4cd88b37c..c16b63a313b 100644
--- a/libgo/go/cmd/cgo/doc.go
+++ b/libgo/go/cmd/cgo/doc.go
@@ -45,8 +45,8 @@ For example:
 	// #include <png.h>
 	import "C"
 
-Alternatively, CPPFLAGS and LDFLAGS may be obtained via the pkg-config
-tool using a '#cgo pkg-config:' directive followed by the package names.
+Alternatively, CPPFLAGS and LDFLAGS may be obtained via the pkg-config tool
+using a '#cgo pkg-config:' directive followed by the package names.
 For example:
 
 	// #cgo pkg-config: png cairo
@@ -55,11 +55,21 @@ For example:
 
 The default pkg-config tool may be changed by setting the PKG_CONFIG environment variable.
 
+For security reasons, only a limited set of flags are allowed, notably -D, -I, and -l.
+To allow additional flags, set CGO_CFLAGS_ALLOW to a regular expression
+matching the new flags. To disallow flags that would otherwise be allowed,
+set CGO_CFLAGS_DISALLOW to a regular expression matching arguments
+that must be disallowed. In both cases the regular expression must match
+a full argument: to allow -mfoo=bar, use CGO_CFLAGS_ALLOW='-mfoo.*',
+not just CGO_CFLAGS_ALLOW='-mfoo'. Similarly named variables control
+the allowed CPPFLAGS, CXXFLAGS, FFLAGS, and LDFLAGS.
+
 When building, the CGO_CFLAGS, CGO_CPPFLAGS, CGO_CXXFLAGS, CGO_FFLAGS and
 CGO_LDFLAGS environment variables are added to the flags derived from
 these directives. Package-specific flags should be set using the
 directives, not the environment variables, so that builds work in
-unmodified environments.
+unmodified environments. Flags obtained from environment variables
+are not subject to the security limitations described above.
 
 All the cgo CPPFLAGS and CFLAGS directives in a package are concatenated and
 used to compile C files in that package. All the CPPFLAGS and CXXFLAGS