vbox: Introduce vboxReportError()

When a VirtualBox API fails it produced an exception. Until now,
we did not have correct APIs wired up to get the exception and
its error message. Thus, we were left with plain:

  virReportError("virtualbox API failed, rc=%08x", rc);

This is not very user friendly because those rc values are hard
to parse (e.g. some values are defined as a sum of a base value
and some other value) and also it expects users to know where to
look.

But now that we have all machinery needed for querying
exceptions, vboxReportError() can be introduced. The aim is to
query VirtualBox exceptions and append them after the error
message we intent to report. If the exception can't be queried
successfully, this behaves exactly like virReportError().

Signed-off-by: Michal Privoznik <mprivozn@redhat.com>
Reviewed-by: Martin Kletzander <mkletzan@redhat.com>

build-aux/syntax-check.mk

@@ -388,6 +388,7 @@ msg_gen_function += lxcError
 msg_gen_function += regerror
 msg_gen_function += vah_error
 msg_gen_function += vah_warning
+msg_gen_function += vboxReportError
 msg_gen_function += virGenericReportError
 msg_gen_function += virRaiseError
 msg_gen_function += virReportError

src/vbox/vbox_common.c

@@ -63,6 +63,119 @@ static struct _vboxDriver *vbox_driver;
 static struct _vboxDriver *vboxDriverObjNew(void);
 static __thread bool vboxDriverDisposed;
 
+#define vboxReportError(errcode, ...) \
+    vboxReportErrorHelper(data, errcode, __FILE__, \
+                          __FUNCTION__, __LINE__, __VA_ARGS__)
+
+static void G_GNUC_PRINTF(6, 7) G_GNUC_UNUSED
+vboxReportErrorHelper(struct _vboxDriver *data,
+                      int errcode,
+                      const char *filename,
+                      const char *funcname,
+                      size_t linenr,
+                      const char *fmt, ...)
+{
+    int save_errno = errno;
+    g_auto(virBuffer) errBuf = VIR_BUFFER_INITIALIZER;
+    nsIException *ex = NULL;
+    IVirtualBoxErrorInfo *ei = NULL;
+    const nsID *vboxErrorInfoIID = NULL;
+    bool multipleLines = false;
+    nsresult rc;
+    g_autofree char *detail = NULL;
+
+    if (fmt) {
+        va_list args;
+
+        va_start(args, fmt);
+        detail = g_strdup_vprintf(fmt, args);
+        va_end(args);
+    }
+
+    rc = gVBoxAPI.UPFN.GetException(data->pFuncs, &ex);
+    if (NS_FAILED(rc) || !ex) {
+        VIR_WARN("failed to get exception object");
+        goto report;
+    }
+
+    vboxErrorInfoIID = gVBoxAPI.UIVirtualBoxErrorInfo.GetIID();
+    rc = VBOX_QUERY_INTERFACE(ex, vboxErrorInfoIID, (void **)&ei);
+    if (NS_FAILED(rc) || !ei) {
+        VIR_WARN("unable to typecast exception object");
+        goto report;
+    }
+
+    while (ei) {
+        IVirtualBoxErrorInfo *ei_next = NULL;
+        PRUnichar *componentUtf16 = NULL;
+        char *componentUtf8 = NULL;
+        PRUnichar *textUtf16 = NULL;
+        char *textUtf8 = NULL;
+
+        rc = gVBoxAPI.UIVirtualBoxErrorInfo.GetComponent(ei, &componentUtf16);
+        if (NS_FAILED(rc)) {
+            VIR_WARN("failed to get error component");
+            goto report;
+        }
+
+        rc = gVBoxAPI.UIVirtualBoxErrorInfo.GetText(ei, &textUtf16);
+        if (NS_FAILED(rc)) {
+            VBOX_UTF16_FREE(componentUtf16);
+            VIR_WARN("failed to get error text");
+            goto report;
+        }
+
+        VBOX_UTF16_TO_UTF8(componentUtf16, &componentUtf8);
+        VBOX_UTF16_FREE(componentUtf16);
+
+        VBOX_UTF16_TO_UTF8(textUtf16, &textUtf8);
+        VBOX_UTF16_FREE(textUtf16);
+
+        virBufferAsprintf(&errBuf, "%s: %s", componentUtf8, textUtf8);
+        VBOX_UTF8_FREE(componentUtf8);
+        VBOX_UTF8_FREE(textUtf8);
+
+        if (multipleLines)
+            virBufferAddChar(&errBuf, '\n');
+        else
+            multipleLines = true;
+
+        rc = gVBoxAPI.UIVirtualBoxErrorInfo.GetNext(ei, &ei_next);
+        if (NS_FAILED(rc)) {
+            break;
+        }
+
+        VBOX_RELEASE(ei);
+        ei = ei_next;
+    }
+
+ report:
+    if (virBufferUse(&errBuf)) {
+        const char *vboxErr = virBufferCurrentContent(&errBuf);
+        g_autofree char *newDetail = NULL;
+
+        if (!detail || STREQ(detail, "")) {
+            newDetail = g_strdup(vboxErr);
+        } else {
+            newDetail = g_strdup_printf("%s: %s", detail, vboxErr);
+        }
+
+        VIR_FREE(detail);
+        detail = g_steal_pointer(&newDetail);
+    }
+
+    virReportErrorHelper(VIR_FROM_THIS, errcode, filename, funcname, linenr, "%s", detail);
+
+    rc = gVBoxAPI.UPFN.ClearException(data->pFuncs);
+    if (NS_FAILED(rc)) {
+        VIR_WARN("failed to clear exception");
+    }
+
+    VBOX_RELEASE(ei);
+    VBOX_RELEASE(ex);
+    errno = save_errno;
+}
+
 static int
 vboxDomainDevicesDefPostParse(virDomainDeviceDef *dev,
                               const virDomainDef *def G_GNUC_UNUSED,