[PATCH 2/4] libxl_get_scheduler() cannot return ERROR_FAIL

[Marcin Cieslak <saper@saper.info>]

ERROR_FAIL (-3) is not a proper value for
libxl_scheduler enum.
Use LIBXL_SCHEDULER_UNKNOWN (0) instead.

Clang complains otherwise:

xl_cmdimpl.c:4824:44: error: comparison of unsigned enum expression < 0 is always false [-Werror,-Wtautological-compare]
    if ((sched = libxl_get_scheduler(ctx)) < 0) {
        ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ^ ~
xl_cmdimpl.c:6705:48: error: comparison of unsigned enum expression < 0 is always false [-Werror,-Wtautological-compare]
        if ((sched = libxl_get_scheduler(ctx)) < 0) {
            ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ^ ~

C99 does not guarantee that enums are ints (they
can be unsigned).
---
 tools/libxl/libxl.c      | 2 +-
 tools/libxl/xl_cmdimpl.c | 4 ++--
 2 files changed, 3 insertions(+), 3 deletions(-)

diff --git a/tools/libxl/libxl.c b/tools/libxl/libxl.c
index ad3495a..785a1e7 100644
--- a/tools/libxl/libxl.c
+++ b/tools/libxl/libxl.c
@@ -4957,7 +4957,7 @@ libxl_scheduler libxl_get_scheduler(libxl_ctx *ctx)
 
     if ((ret = xc_sched_id(ctx->xch, (int *)&sched)) != 0) {
         LIBXL__LOG_ERRNO(ctx, LIBXL__LOG_ERROR, "getting domain info list");
-        return ERROR_FAIL;
+        return LIBXL_SCHEDULER_UNKNOWN;
     }
     return sched;
 }
diff --git a/tools/libxl/xl_cmdimpl.c b/tools/libxl/xl_cmdimpl.c
index 8a38077..86daf8e 100644
--- a/tools/libxl/xl_cmdimpl.c
+++ b/tools/libxl/xl_cmdimpl.c
@@ -4821,7 +4821,7 @@ static void output_xeninfo(void)
         return;
     }
 
-    if ((sched = libxl_get_scheduler(ctx)) < 0) {
+    if ((sched = libxl_get_scheduler(ctx)) == LIBXL_SCHEDULER_UNKNOWN) {
         fprintf(stderr, "get_scheduler sysctl failed.\n");
         return;
     }
@@ -6702,7 +6702,7 @@ int main_cpupoolcreate(int argc, char **argv)
             goto out_cfg;
         }
     } else {
-        if ((sched = libxl_get_scheduler(ctx)) < 0) {
+        if ((sched = libxl_get_scheduler(ctx)) == LIBXL_SCHEDULER_UNKNOWN) {
             fprintf(stderr, "get_scheduler sysctl failed.\n");
             goto out_cfg;
         }
-- 
2.0.2