[Xen-devel] [PATCH v3 6/8] golang/xenlight: Don't leak memory on context open failure

[George Dunlap <george.dunlap@citrix.com>]

If libxl_ctx_alloc() returns an error, we need to destroy the logger
that we made.

Restructure the Close() method such that it checks for each resource
to be freed and then frees it.  This allows Close() to be come
idempotent, as well as to be a useful clean-up to a partially-created
context.

Signed-off-by: George Dunlap <george.dunlap@citrix.com>
---
CC: Nick Rosbrook <rosbrookn@ainfosec.com>
---
 tools/golang/xenlight/xenlight.go | 30 +++++++++++++++++++++---------
 1 file changed, 21 insertions(+), 9 deletions(-)

diff --git a/tools/golang/xenlight/xenlight.go b/tools/golang/xenlight/xenlight.go
index 0e71f6ca7d..662b266250 100644
--- a/tools/golang/xenlight/xenlight.go
+++ b/tools/golang/xenlight/xenlight.go
@@ -79,28 +79,40 @@ type Context struct {
 }
 
 // NewContext returns a new Context.
-func NewContext() (*Context, error) {
-	var ctx Context
+func NewContext() (ctx *Context, err error) {
+	ctx = &Context{}
+
+	defer func() {
+		if err != nil {
+			ctx.Close()
+			ctx = nil
+		}
+	}()
 
 	ctx.logger = C.xtl_createlogger_stdiostream(C.stderr, C.XTL_DEBUG, 0)
 
 	ret := C.libxl_ctx_alloc(&ctx.ctx, C.LIBXL_VERSION, 0,
 		(*C.xentoollog_logger)(unsafe.Pointer(ctx.logger)))
 	if ret != 0 {
-		return nil, Error(ret)
+		return ctx, Error(ret)
 	}
 
-	return &ctx, nil
+	return ctx, nil
 }
 
 // Close closes the Context.
 func (ctx *Context) Close() error {
-	ret := C.libxl_ctx_free(ctx.ctx)
-	ctx.ctx = nil
-	C.xtl_logger_destroy((*C.xentoollog_logger)(unsafe.Pointer(ctx.logger)))
+	if ctx.ctx != nil {
+		ret := C.libxl_ctx_free(ctx.ctx)
+		if ret != 0 {
+			return Error(ret)
+		}
+		ctx.ctx = nil
+	}
 
-	if ret != 0 {
-		return Error(ret)
+	if ctx.logger != nil {
+		C.xtl_logger_destroy((*C.xentoollog_logger)(unsafe.Pointer(ctx.logger)))
+		ctx.logger = nil
 	}
 
 	return nil
-- 
2.24.1


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