fix(scheduler): put_resvals treats resource idx 0 as invalid → SEGV

put_resvals (resource.c) used `idxs[i] <= 0` to skip "invalid" resource
indexes, but index 0 IS valid — it's the first resource in the table
(e.g. "slots"). For idx 0 the val was never allocated (xvals[i] stayed
NULL) and the write loop then SEGV'd. bug-1495.

Fix: skip only negative indexes (`idxs[i] < 0`), and NULL-guard the
write loop defensively.

Verified end-to-end: a locally-built scheduler now connects to the t1
controller and dispatches all 5 test jobs to node t1 (exec_hosts
populated, jobs run and exit). This was the final blocker for job
scheduling (bug-1494: all jobs PEND).

Also: add the t1 host definition to hosts.yaml (worker join was rejected
with -EINVAL because no matching hostconfig existed for hostname "t1").

Co-Authored-By: Claude <noreply@anthropic.com>

src/configs/hosts.yaml

@@ -35,6 +35,15 @@ hosts:
     model: "x86_64-linux-gnu"
     max_slot: 128
 
+    # t1: primary test node (172.31.1.30). Must match the hostname the worker
+    # reports via gethostname(); without a matching hostconfig, the worker's
+    # join is rejected with -EINVAL (find_matched_hostconfig fails) and no
+    # compute node ever registers, so every job stays PEND (bug-1494).
+  - hostname: t1
+    type: "x86_64-linux-gnu"
+    model: "x86_64-linux-gnu"
+    max_slot: 8
+
 
 hostgroups:
   - groupname: hg1

src/scheduler/src/resource.c

@@ -69,7 +69,10 @@ int put_resvals(zarray_t* array, int nres, int* idxs, float* vals)
     }
 
     for (i = 0; i < nres; i++) {
-        if (idxs[i] <= 0) {
+        /* A resource index of 0 is VALID (the first resource — e.g. "slots").
+         * Only negative indexes are invalid. bug-1495: the old `<= 0` skipped
+         * idx 0, leaving xvals[i] NULL and then SEGV on the write below. */
+        if (idxs[i] < 0) {
             continue;
         }
 
@@ -87,6 +90,9 @@ int put_resvals(zarray_t* array, int nres, int* idxs, float* vals)
     }
 
     for (i = 0; i < nres; i++) {
+        if (xvals[i] == NULL) {
+            continue; /* defensive: idx<0 skipped, or allocation failed above */
+        }
         xvals[i]->u.fvalue = vals[i];
     }