virterror: Add virSetError

Can be used to re-set an old error, which may have been squashed by
other functions (like cleanup routines). Will be used in subsequent patches

src/libvirt_private.syms

@@ -593,6 +593,7 @@ virRaiseErrorFull;
 virReportSystemErrorFull;
 virReportOOMErrorFull;
 virStrerror;
+virSetError;
 
 
 # xml.h

src/util/virterror.c

@@ -289,6 +289,28 @@ virGetLastError(void)
     return err;
 }
 
+/**
+ * virSetError:
+ *
+ * Set the current error from a previously saved error object
+ *
+ * Can be used to re-set an old error, which may have been squashed by
+ * other functions (like cleanup routines).
+ *
+ * Returns 0 on success, 1 on failure
+ */
+int
+virSetError(virErrorPtr newerr)
+{
+    virErrorPtr err;
+    err = virGetLastError();
+    if (!err)
+        return -1;
+
+    virResetError(err);
+    return virCopyError(newerr, err);
+}
+
 /**
  * virCopyLastError:
  * @to: target to receive the copy

src/util/virterror_internal.h

@@ -90,6 +90,7 @@ void virReportOOMErrorFull(virConnectPtr conn,
                      __FILE__, __FUNCTION__, __LINE__)
 
 
+int virSetError(virErrorPtr newerr);
 void virDispatchError(virConnectPtr conn);
 const char *virStrerror(int theerrno, char *errBuf, size_t errBufLen);