test/wcc: extend carrier ownership to the bootstrap and platform gates

Same contract as the 27 repaired byte/artifact survivors: checked
acquisition, one all-exit cleanup funnel per carrier, ENOENT-tolerant
checked unlinks, exact-path deletion, and cleanup failure fails a
passing carrier without overwriting its diagnostic. Also closes the
vacuous-green channels: empty-artifact pairs no longer byte-compare
equal, capture and staging failures fail their row loudly, 950 requires
a clean checker exit on no-error rows and hard-fails on a missing
wwdump_ww, 992 keys its scratch per invocation so a failed cleanup
cannot leak stale objects into the next tool's compare, and 995 no
longer pre-sweeps a workdir it never created. No assertion is weakened;
990_selfhost is retired in the next commit rather than repaired.

test/wcc/994_w6c_ww.c

@@ -15,6 +15,7 @@
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
+#include <errno.h>
 #include <unistd.h>
 #include <sys/wait.h>
 #include <dirent.h>
@@ -65,6 +66,9 @@ static int
 diff_one(const char *bin, const char *label, const char *src)
 {
 	char ws[64], cs[64], cmd[2048];
+	char *bw = NULL, *bc = NULL;
+	size_t nw = 0, nc = 0;
+	int rc = -1;
 	snprintf(ws, sizeof ws, "/tmp/wwc6_%d_w.s", getpid());
 	snprintf(cs, sizeof cs, "/tmp/wwc6_%d_c.s", getpid());
 
@@ -72,28 +76,37 @@ diff_one(const char *bin, const char *label, const char *src)
 	    bin, src, ws);
 	if (runwait(cmd) != 0) {
 		fprintf(stderr, "w6c_ww FAIL: wwdump_ww -c errored on %s\n", label);
-		unlink(ws);
-		return -1;
+		goto cleanup;
 	}
 	snprintf(cmd, sizeof cmd, "timeout 180 %s/w6c_ww -o %s %s 2>/dev/null", bin, cs, src);
 	if (runwait(cmd) != 0) {
 		fprintf(stderr, "w6c_ww FAIL: w6c_ww errored on %s\n", label);
-		unlink(ws); unlink(cs);
-		return -1;
+		goto cleanup;
 	}
-	char *bw = NULL, *bc = NULL;
-	size_t nw = 0, nc = 0;
-	int rc = 0;
 	if (slurp(ws, &bw, &nw) < 0 || slurp(cs, &bc, &nc) < 0) {
 		fprintf(stderr, "w6c_ww FAIL: cannot read .s for %s\n", label);
-		rc = -1;
+	} else if (nw == 0) {
+		fprintf(stderr, "w6c_ww FAIL: empty .s for %s\n", label);
 	} else if (nw != nc || memcmp(bw, bc, nw) != 0) {
 		fprintf(stderr, "w6c_ww FAIL: %s — wwdump_ww %zu vs w6c_ww %zu bytes\n",
 		    label, nw, nc);
-		rc = -1;
-	}
+	} else
+		rc = 0;
+
+cleanup:
 	free(bw); free(bc);
-	unlink(ws); unlink(cs);
+	/* cs may not exist when w6c_ww never ran or died before -o. */
+	int cleanfail = 0;
+	if (unlink(ws) != 0 && errno != ENOENT) {
+		perror(ws);
+		cleanfail = 1;
+	}
+	if (unlink(cs) != 0 && errno != ENOENT) {
+		perror(cs);
+		cleanfail = 1;
+	}
+	if (cleanfail && rc == 0)
+		rc = -1;
 	return rc;
 }
 
@@ -103,7 +116,15 @@ write_file(const char *path, const char *content)
 	FILE *f = fopen(path, "wb");
 	if (!f) return -1;
 	wwtest_fputs(content, f);
-	fclose(f);
+	/* wwtest_fputs is void; ferror is the only short-write witness. */
+	int bad = ferror(f);
+	if (fclose(f) != 0) bad = 1;
+	if (bad) {
+		perror(path);
+		if (unlink(path) != 0 && errno != ENOENT)
+			perror(path);
+		return -1;
+	}
 	return 0;
 }
 
@@ -282,7 +303,10 @@ main(void)
 		snprintf(src, sizeof src, "/tmp/wwc6_%d_%d.ww", getpid(), i);
 		if (write_file(src, progs[i].src) != 0) { fail++; n++; continue; }
 		if (diff_one(bin, progs[i].label, src) != 0) fail++;
-		unlink(src);
+		if (unlink(src) != 0 && errno != ENOENT) {
+			perror(src);
+			fail++;
+		}
 		n++;
 	}
 
@@ -321,7 +345,14 @@ main(void)
 			    bad[i].label);
 			fail++;
 		}
-		unlink(src); unlink(s);
+		if (unlink(src) != 0 && errno != ENOENT) {
+			perror(src);
+			fail++;
+		}
+		if (unlink(s) != 0 && errno != ENOENT) {
+			perror(s);
+			fail++;
+		}
 		n++;
 	}
 
@@ -371,7 +402,11 @@ main(void)
 		for (int s = 0; s < 2; s++) {
 			snprintf(cmd, sizeof cmd, "rm -rf %s %s.sepwork %s.cache",
 			    stg[s].prog, stg[s].prog, stg[s].prog);
-			runwait(cmd);
+			if (runwait(cmd) != 0) {
+				fprintf(stderr, "Tier-C: cleanup %s failed\n",
+				    stg[s].prog);
+				fail++;
+			}
 		}
 	}