[PATCH v2 2/5] libxl: make GC_FREE reachable in libxl_get_scheduler()

[Chester Lin <czylin@uwaterloo.ca>]

Coverity CID 1343309

Make GC_FREE reachable in all cases in libxl_get_scheduler() by
eliminating the error-path return and instead storing the error code in
the returned variable.

To make this semantically consistent, change the return type of
libxl_get_scheduler() from libxl_scheduler to int, and make a note of
the interpretation of the return value in libxl.h.  N.B. This change
breaks neither the API nor the ABI of libxl.

Suggested-by: Ian Campbell <ian.campbell@citrix.com>
Signed-off-by: Chester Lin <czylin@uwaterloo.ca>

---
Changed return type of libxl_get_scheduler in order to return both negative
error constants and positive scheduler values.
---
 tools/libxl/libxl.c | 11 +++++------
 tools/libxl/libxl.h |  5 ++++-
 2 files changed, 9 insertions(+), 7 deletions(-)

diff --git a/tools/libxl/libxl.c b/tools/libxl/libxl.c
index 7f28af8..96b6333 100644
--- a/tools/libxl/libxl.c
+++ b/tools/libxl/libxl.c
@@ -5583,19 +5583,18 @@ out:
     return rc;
 }
 
-libxl_scheduler libxl_get_scheduler(libxl_ctx *ctx)
+int libxl_get_scheduler(libxl_ctx *ctx)
 {
-    int r, sched;
+    int r, ret;
 
     GC_INIT(ctx);
-    r = xc_sched_id(ctx->xch, &sched);
+    r = xc_sched_id(ctx->xch, &ret);
     if (r != 0) {
         LOGE(ERROR, "getting current scheduler id");
-        return ERROR_FAIL;
-        GC_FREE;
+        ret = ERROR_FAIL;
     }
     GC_FREE;
-    return sched;
+    return ret;
 }
 
 static int sched_arinc653_domain_set(libxl__gc *gc, uint32_t domid,
diff --git a/tools/libxl/libxl.h b/tools/libxl/libxl.h
index 05606a7..6f53376 100644
--- a/tools/libxl/libxl.h
+++ b/tools/libxl/libxl.h
@@ -1702,7 +1702,10 @@ int libxl_domain_get_nodeaffinity(libxl_ctx *ctx, uint32_t domid,
                                   libxl_bitmap *nodemap);
 int libxl_set_vcpuonline(libxl_ctx *ctx, uint32_t domid, libxl_bitmap *cpumap);
 
-libxl_scheduler libxl_get_scheduler(libxl_ctx *ctx);
+/* A return value less than 0 should be interpreted as a libxl_error, while a
+ * return value greater than or equal to 0 should be interpreted as a
+ * libxl_scheduler. */
+int libxl_get_scheduler(libxl_ctx *ctx);
 
 /* Per-scheduler parameters */
 int libxl_sched_credit_params_get(libxl_ctx *ctx, uint32_t poolid,
-- 
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