libxenlight: Clean up logging arrangements

* Introduce new variants of the logging functions which include
  errno values (converted using strerror) in the messages passed to
  the
  application's logging callback.

* Use the new errno-including logging functions everywhere where
  appropriate.  In general, xc_... functions return errno values or 0;
  xs_... functions return 0 or -1 (or some such) setting errno.

* When libxl_xs_get_dompath fails, do not treat it as an allocation
  error.  It isn't: it usually means xenstored failed.

* Remove many spurious \n's from log messages.  (The applications log
  callback is expected to add a \n if it wants to do that, so libxl's
  logging functions should be passed strings without \n.)

Signed-off-by: Ian Jackson <Ian.Jackson@eu.citrix.com>

1 files changed, 5 insertions, 0 deletions

diff --git a/tools/libxl/libxl_xshelp.c b/tools/libxl/libxl_xshelp.c
index 6286d02826..f59eee7523 100644
--- a/tools/libxl/libxl_xshelp.c
+++ b/tools/libxl/libxl_xshelp.c
@@ -95,6 +95,11 @@ char * libxl_xs_read(struct libxl_ctx *ctx, xs_transaction_t t, char *path)
 char *libxl_xs_get_dompath(struct libxl_ctx *ctx, uint32_t domid)
 {
     char *s = xs_get_domain_path(ctx->xsh, domid);
+    if (!s) {
+        XL_LOG_ERRNO(ctx, XL_LOG_ERROR, "failed to get dompath for %lu",
+                     domid);
+        return NULL;
+    }
     libxl_ptr_add(ctx, s);
     return s;
 }