12:23 a.m.
The current "arg_string_list" and "free_string_list" implementations
go
back to commit b6f01f32606d ("Add Go (language) bindings.", 2013-07-03).
There are two problems with them:
- "free_string_list" doesn't actually free anything,
- at the *first* such g.Internal_test() call site that passes an
Ostringlist member inside the Optargs argument, namely:
g.Internal_test ("abc",
string_addr ("def"),
[]string{},
false,
0,
0,
"123",
"456",
[]byte{'a', 'b', 'c', '\000',
'a', 'b', 'c'},
&guestfs.OptargsInternal_test{Ostringlist_is_set: true,
Ostringlist: []string{}
}
)
the "golang/run-bindtests" case crashes:
panic: runtime error: cgo argument has Go pointer to Go pointer
goroutine 1 [running]:
libguestfs.org/guestfs.(*Guestfs).Internal_test.func7(0xc000018180,
0xadfb60, 0xadfb80, 0xc000010048, 0x0, 0x0, 0x0, 0xae3e10, 0xae3e30,
0xade3a0, ...)
golang/src/libguestfs.org/guestfs/guestfs.go:6729 +0xa9
libguestfs.org/guestfs.(*Guestfs).Internal_test(0xc000018180, 0x4ee3a5,
0x3, 0xc000061be8, 0xc000061af8, 0x0, 0x0, 0xc000061a00, 0x0, 0x0, ...)
golang/src/libguestfs.org/guestfs/guestfs.go:6729 +0x3c9
main.main()
golang/bindtests/bindtests.go:77 +0x151e
exit status 2
FAIL run-bindtests (exit status: 1)
It turns out that a C-language array containing C-language pointers can
only be allocated in C:
https://stackoverflow.com/questions/35924545/golang-cgo-panic-runtime-err...
Rewrite the "arg_string_list" and "free_string_list" functions almost
entirely in C.
Signed-off-by: Laszlo Ersek <lersek(a)redhat.com>
---
generator/golang.ml | 46 ++++++++++++++++++++++++++++++++++++---------
1 file changed, 37 insertions(+), 9 deletions(-)
diff --git a/generator/golang.ml b/generator/golang.ml
index d328abe4ed08..5db478e8a494 100644
--- a/generator/golang.ml
+++ b/generator/golang.ml
@@ -52,6 +52,39 @@ _go_guestfs_create_flags (unsigned flags)
{
return guestfs_create_flags (flags);
}
+
+//
+// A C-language array of C-language pointers needs to be allocated in C.
+//
https://stackoverflow.com/questions/35924545/golang-cgo-panic-runtime-err...
+//
+typedef char *pChar;
+
+pChar *allocStringArray (size_t nmemb)
+{
+ pChar *array;
+
+ array = malloc (sizeof (pChar) * (nmemb + 1));
+ array[nmemb] = NULL;
+ return array;
+}
+
+void storeString (pChar *array, size_t idx, pChar string)
+{
+ array[idx] = string;
+}
+
+void freeStringArray (pChar *array)
+{
+ pChar *position;
+ pChar string;
+
+ position = array;
+ while ((string = *position) != NULL) {
+ free (string);
+ position++;
+ }
+ free (array);
+}
*/
import \"C\"
@@ -148,12 +181,11 @@ func (g *Guestfs) Close () *GuestfsError {
* C strings and golang []string.
*/
func arg_string_list (xs []string) **C.char {
- r := make ([]*C.char, 1 + len (xs))
+ r := C.allocStringArray (C.size_t (len (xs)))
for i, x := range xs {
- r[i] = C.CString (x)
+ C.storeString (r, C.size_t (i), C.CString (x));
}
- r[len (xs)] = nil
- return &r[0]
+ return (**C.char) (r)
}
func count_string_list (argv **C.char) int {
@@ -167,11 +199,7 @@ func count_string_list (argv **C.char) int {
}
func free_string_list (argv **C.char) {
- for *argv != nil {
- //C.free (*argv)
- argv = (**C.char) (unsafe.Pointer (uintptr (unsafe.Pointer (argv)) +
- unsafe.Sizeof (*argv)))
- }
+ C.freeStringArray ((*C.pChar) (argv))
}
func return_string_list (argv **C.char) []string {
--
2.19.1.3.g30247aa5d201