P2 cleanup: comments, make_fake_api stack alloc, find_str_param fix

1. test_plocks.c: add comment to test_upgrade_under_contention clarifying
   it verifies towrlock completion and holding_wrlock; notes that concurrent
   exclusivity is covered by test_stress().

2. test_pfsupload.c / make_fake_api: replace static-local psock_t with
   caller-supplied stack allocation (out parameter) to eliminate the
   multiple-calls-per-test footgun.

3. test_pfsupload.c / find_str_param: replace ternary
   `paramnamelen == strlen ? paramname : ""` with explicit length check +
   strncmp, matching the cleaner pattern used in find_num_param.

4. Makefile: add comment next to -Wl,--wrap=papi_send noting it redirects
   papi_send to __wrap_papi_send and is GNU ld only (not macOS Apple ld).

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Makefile

@@ -236,7 +236,7 @@ tests/test_plocks: $(UNIT_DIR)/test_plocks.c $(LIBDIR)/plocks.c $(LIBDIR)/pdbg.c
 
 tests/test_pfsupload: $(UNIT_DIR)/test_pfsupload.c $(LIBDIR)/pfsupload_send.c $(LIBDIR)/pdbg.c $(LIBDIR)/pmem.c $(LIBDIR)/putil.c $(LIBDIR)/ppath.c tests/stubs/test_stubs.c
 	$(CC) $(TEST_CFLAGS) $(CFLAGS) -o $@ $^ \
-		-Wl,--wrap=papi_send
+		-Wl,--wrap=papi_send  # redirect papi_send → __wrap_papi_send; GNU ld only (not macOS Apple ld)
 
 tests/test_read_response: $(UNIT_DIR)/test_read_response.cpp rpcclient.cpp tests/stubs/test_stubs_cpp.c
 	$(CXX) $(TEST_CXXFLAGS) $(CXXFLAGS) -o $@ $^

tests/unit-tests/test_pfsupload.c

@@ -80,10 +80,11 @@ static void reset_wrap(void) {
 /* Find a string parameter by name; returns its value or NULL */
 static const char *find_str_param(const char *name) {
     if (!g_last_params) return NULL;
+    size_t nlen = strlen(name);
     for (size_t i = 0; i < g_last_nparams; i++) {
         if (g_last_params[i].paramtype == PARAM_STR &&
-            strcmp(g_last_params[i].paramnamelen == strlen(name) ?
-                   g_last_params[i].paramname : "", name) == 0)
+            g_last_params[i].paramnamelen == nlen &&
+            strncmp(g_last_params[i].paramname, name, nlen) == 0)
             return g_last_params[i].str;
     }
     return NULL;
@@ -103,13 +104,13 @@ static int find_num_param(const char *name, uint64_t *out) {
     return 0;
 }
 
-/* Build a minimal fake psock_t wrapping one end of a socketpair */
-static psock_t *make_fake_api(int sv[2]) {
-    static psock_t fake;
+/* Build a minimal fake psock_t wrapping one end of a socketpair.
+ * The caller provides a stack-allocated psock_t; no static storage is used
+ * so multiple calls within the same test function are safe. */
+static void make_fake_api(psock_t *out, int sv[2]) {
     socketpair(AF_UNIX, SOCK_STREAM, 0, sv);
-    memset(&fake, 0, sizeof(fake));
-    fake.sock = sv[1];
-    return &fake;
+    memset(out, 0, sizeof(*out));
+    out->sock = sv[1];
 }
 
 /* ------------------------------------------------------------------ */
@@ -128,7 +129,7 @@ static void task_init(fsupload_task_t *t) {
 static void test_send_mkdir_basic(void) {
     reset_wrap();
     int sv[2];
-    psock_t *api = make_fake_api(sv);
+    psock_t api_s; make_fake_api(&api_s, sv); psock_t *api = &api_s;
 
     fsupload_task_t task;
     task_init(&task);
@@ -155,7 +156,7 @@ static void test_send_mkdir_basic(void) {
 static void test_send_mkdir_encrypted(void) {
     reset_wrap();
     int sv[2];
-    psock_t *api = make_fake_api(sv);
+    psock_t api_s; make_fake_api(&api_s, sv); psock_t *api = &api_s;
 
     fsupload_task_t task;
     task_init(&task);
@@ -183,7 +184,7 @@ static void test_send_mkdir_encrypted(void) {
 static void test_send_rmdir(void) {
     reset_wrap();
     int sv[2];
-    psock_t *api = make_fake_api(sv);
+    psock_t api_s; make_fake_api(&api_s, sv); psock_t *api = &api_s;
 
     fsupload_task_t task;
     task_init(&task);
@@ -210,7 +211,7 @@ static void test_api_error_path(void) {
     reset_wrap();
     g_wrap_rc = 0;  /* simulate papi_send failure */
     int sv[2];
-    psock_t *api = make_fake_api(sv);
+    psock_t api_s; make_fake_api(&api_s, sv); psock_t *api = &api_s;
 
     fsupload_task_t task;
     task_init(&task);

tests/unit-tests/test_plocks.c

@@ -141,6 +141,13 @@ static void *upgrade_reader_thread(void *arg) {
     return NULL;
 }
 
+/*
+ * test_upgrade_under_contention verifies that plocks_towrlock() completes
+ * (returns 0) and that the upgrading thread holds the write lock on return.
+ * Concurrent exclusivity — that no reader is simultaneously active once the
+ * write lock is granted — is covered by the counter-integrity check in
+ * test_stress().
+ */
 static void test_upgrade_under_contention(void) {
     struct upgrade_state s;
     plocks_init(&s.rw);