[Xen-devel] [PATCH v3 2/8] go/xenlight: Fix CpuidPoliclyList conversion

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

Empty Go strings should be converted to `nil` libxl_cpuid_policy_list;
otherwise libxl_cpuid_parse_config gets confused.

Also, libxl_cpuid_policy_list returns a weird error, not a "normal"
libxl error; if it returns one of these non-standard errors, convert
it to ErrorInval.

Finally, make the fromC() method take a pointer, and set the value of
CpuidPolicyList such that it will generate a valid CpuidPolicyList in
response.

Signed-off-by: George Dunlap <george.dunlap@citrix.com>
---
v2:
- Port over toC() function signature change
- Have fromC set the string to ""

CC: Nick Rosbrook <rosbrookn@ainfosec.com>
---
 tools/golang/xenlight/xenlight.go | 10 ++++++++--
 1 file changed, 8 insertions(+), 2 deletions(-)

diff --git a/tools/golang/xenlight/xenlight.go b/tools/golang/xenlight/xenlight.go
index b1587b964f..1299981713 100644
--- a/tools/golang/xenlight/xenlight.go
+++ b/tools/golang/xenlight/xenlight.go
@@ -306,9 +306,14 @@ func (el *EvLink) toC(cel *C.libxl_ev_link) (err error) { return }
 // empty when it is returned from libxl.
 type CpuidPolicyList string
 
-func (cpl CpuidPolicyList) fromC(ccpl *C.libxl_cpuid_policy_list) error { return nil }
+func (cpl *CpuidPolicyList) fromC(ccpl *C.libxl_cpuid_policy_list) error { *cpl = ""; return nil }
 
 func (cpl CpuidPolicyList) toC(ccpl *C.libxl_cpuid_policy_list) error {
+	if cpl == "" {
+		*ccpl = nil
+		return nil
+	}
+
 	s := C.CString(string(cpl))
 	defer C.free(unsafe.Pointer(s))
 
@@ -316,7 +321,8 @@ func (cpl CpuidPolicyList) toC(ccpl *C.libxl_cpuid_policy_list) error {
 	if ret != 0 {
 		C.libxl_cpuid_dispose(ccpl)
 
-		return Error(-ret)
+		// libxl_cpuid_parse_config doesn't return a normal libxl error.
+		return ErrorInval
 	}
 
 	return nil
-- 
2.24.1


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