src: resolve various cov-scan warnings

pdu_processor_init:
CID 1635250: (#1 of 1): Using a moved object (USE_AFTER_MOVE)
3. return_with_moved_parameter: Returning while reference parameter
names is in a moved state.

do_perftest:
CID 1635246: (#2 of 2): Division or modulo by zero (DIVIDE_BY_ZERO)
4. divide_by_zero: In function call operator /, division by
expression fcount which may be zero has undefined behavior.

timeindex_delete:
CID 1635249: (#1 of 1): Use of auto that causes a copy (AUTO_CAUSES_COPY)
auto_causes_copy: Using the auto keyword without an & causes the copy
of an object of type std::string.
[False positive; there is copy elision happening here.]

oxcmail_export:
CID 1635241: (#1 of 1): Unchecked return value (CHECKED_RETURN)
106. check_return: Calling set_field without checking return value
(as is done elsewhere 56 out of 70 times).

mt2exm:
CID 1635240: (#2 of 2): Using a moved object (USE_AFTER_MOVE)
19. use_after_move: digest is used after it has been already moved.

Author: jengelh

exch/exmdb/common_util.cpp

@@ -4720,7 +4720,7 @@ bool timeindex_delete(sqlite3 *db, uint64_t fid, uint64_t mid)
 {
 	if (fid == 0)
 		return true;
-	auto q = mid == 0 ?
+	const auto &q = mid == 0 ?
 		fmt::format("DELETE FROM msgtime_index WHERE folder_id={}", fid) :
 		fmt::format("DELETE FROM msgtime_index WHERE folder_id={} AND message_id={}", fid, mid);
 	return gx_sql_exec(db, q) == SQLITE_OK;

exch/http/pdu_processor.cpp

@@ -186,7 +186,7 @@ static size_t pdu_processor_ndr_stack_size(NDR_STACK_ROOT *pstack_root, int type
 
 void pdu_processor_init(int connection_num, const char *netbios_name,
     const char *dns_name, const char *dns_domain, BOOL header_signing,
-    size_t max_request_mem, const std::span<const static_module> &names)
+    size_t max_request_mem, std::span<const static_module> &&names)
 {
 	static constexpr unsigned int connection_ratio = 10;
 	union {

exch/http/pdu_processor.hpp

@@ -103,7 +103,7 @@ struct BLOB_NODE {
 	DATA_BLOB blob;
 };
 
-extern void pdu_processor_init(int connection_num, const char *netbios_name, const char *dns_name, const char *dns_domain, BOOL header_signing, size_t max_request_mem, const std::span<const gromox::static_module> &names);
+extern void pdu_processor_init(int connection_num, const char *netbios_name, const char *dns_name, const char *dns_domain, BOOL header_signing, size_t max_request_mem, std::span<const gromox::static_module> &&names);
 extern int pdu_processor_run();
 extern void pdu_processor_stop();
 extern std::unique_ptr<PDU_PROCESSOR> pdu_processor_create(const char *host, uint16_t tcp_port);

lib/mapi/oxcmail.cpp

@@ -3619,7 +3619,8 @@ static BOOL oxcmail_export_mail_head(const MESSAGE_CONTENT *pmsg,
 	if (str != nullptr && !phead->set_field("Content-Location", str))
 		return FALSE;
 
-	phead->set_field("X-Mailer", "gromox-oxcmail " PACKAGE_VERSION);
+	if (!phead->set_field("X-Mailer", "gromox-oxcmail " PACKAGE_VERSION))
+		/* ignore */;
 	auto guid = PS_INTERNET_HEADERS;
 	for (size_t i = 0; i < pmsg->proplist.count; ++i) {
 		auto proptag = pmsg->proplist.ppropval[i].proptag;

tools/mbop_locale.cpp

@@ -35,6 +35,8 @@ static void do_perftest(const char *lang)
 		auto delta = now - t_start;
 		if (delta < std::chrono::seconds(1))
 			continue;
+		if (fcount == 0)
+			fcount = 1; /* calm static-analyzer */
 		auto d = std::chrono::duration_cast<std::chrono::microseconds>(delta) / fcount;
 		fprintf(stderr, "\r\e[2K%llu µs\e[K", static_cast<unsigned long long>(d.count()));
 		t_start = now;

tools/mt2exm.cpp

@@ -380,7 +380,7 @@ static int exm_folder(const ob_desc &obd, TPROPVAL_ARRAY &props,
 }
 
 static int exm_create_msg(uint64_t parent_fld, MESSAGE_CONTENT *ctnt,
-    const std::string &im_repr, Json::Value &&digest)
+    const std::string &im_repr, Json::Value &digest)
 {
 	uint64_t msg_id = 0, change_num = 0;
 	if (!exmdb_client->allocate_message_id(g_storedir, parent_fld, &msg_id)) {
@@ -421,6 +421,7 @@ static int exm_create_msg(uint64_t parent_fld, MESSAGE_CONTENT *ctnt,
 		return -EIO;
 	}
 	auto djson = json_to_str(digest);
+	digest["file"].clear();
 
 	uint64_t outmid = 0, outcn = 0;
 	if (!exmdb_client->write_message(g_storedir, CP_UTF8, parent_fld,
@@ -562,7 +563,7 @@ static int exm_message(const ob_desc &obd, MESSAGE_CONTENT &ctnt,
 			if (i > 0 && i % 1024 == 0)
 				fprintf(stderr, "mt2exm repeat %u/%u\n", i, g_repeat_iter);
 			auto ret = exm_create_msg(folder_it->second.fid_to,
-			           &ctnt, im_repr, std::move(digest));
+			           &ctnt, im_repr, digest);
 			if (ret != EXIT_SUCCESS)
 				return ret;
 		}