diff --git a/deltachat-ffi/src/lib.rs b/deltachat-ffi/src/lib.rs
index a477a59b1..3d50d10da 100644
--- a/deltachat-ffi/src/lib.rs
+++ b/deltachat-ffi/src/lib.rs
@@ -111,7 +111,7 @@ pub unsafe extern "C" fn dc_get_config(
     match config::Config::from_str(dc_tools::as_str(key)) {
         Ok(key) => {
             let value = context.get_config(key).unwrap_or_default();
-            into_cstring(value)
+            dc_tools::to_cstring(value)
         }
         Err(_) => std::ptr::null_mut(),
     }
@@ -137,7 +137,7 @@ pub unsafe extern "C" fn dc_get_oauth2_url(
     let addr = dc_tools::to_string(addr);
     let redirect = dc_tools::to_string(redirect);
     match oauth2::dc_get_oauth2_url(context, addr, redirect) {
-        Some(res) => libc::strdup(dc_tools::to_cstring(res).as_ptr()),
+        Some(res) => dc_tools::to_cstring(res),
         None => std::ptr::null_mut(),
     }
 }
@@ -1546,7 +1546,3 @@ fn as_opt_str<'a>(s: *const libc::c_char) -> Option<&'a str> {
 
     Some(dc_tools::as_str(s))
 }
-
-unsafe fn into_cstring(s: impl AsRef<str>) -> *mut libc::c_char {
-    dc_tools::dc_strdup(dc_tools::to_cstring(s).as_ptr())
-}
diff --git a/examples/repl/cmdline.rs b/examples/repl/cmdline.rs
index 3138be865..9d6be9097 100644
--- a/examples/repl/cmdline.rs
+++ b/examples/repl/cmdline.rs
@@ -139,7 +139,7 @@ unsafe fn poke_spec(context: &Context, spec: *const libc::c_char) -> libc::c_int
         } else {
             current_block = 7149356873433890176;
         }
-        real_spec = strdup(to_cstring(rs.unwrap_or_default()).as_ptr());
+        real_spec = to_cstring(rs.unwrap_or_default());
     }
     match current_block {
         8522321847195001863 => {}
@@ -177,10 +177,10 @@ unsafe fn poke_spec(context: &Context, spec: *const libc::c_char) -> libc::c_int
                             let path_plus_name = format!("{}/{}", as_str(real_spec), name);
                             info!(context, 0, "Import: {}", path_plus_name);
                             let path_plus_name_c = to_cstring(path_plus_name);
-
-                            if 0 != dc_poke_eml_file(context, path_plus_name_c.as_ptr()) {
+                            if 0 != dc_poke_eml_file(context, path_plus_name_c) {
                                 read_cnt += 1
                             }
+                            free(path_plus_name_c as *mut _);
                         }
                     }
                     current_block = 1622411330066726685;
@@ -380,18 +380,16 @@ pub unsafe fn dc_cmdline(context: &Context, line: &str) -> Result<(), failure::E
     let mut args = line.splitn(3, ' ');
     let arg0 = args.next().unwrap_or_default();
     let arg1 = args.next().unwrap_or_default();
-    let arg1_c = to_cstring(arg1);
-    let arg1_c_ptr = if arg1.is_empty() {
+    let arg1_c = if arg1.is_empty() {
         std::ptr::null()
     } else {
-        arg1_c.as_ptr()
+        to_cstring(arg1) as *const _
     };
     let arg2 = args.next().unwrap_or_default();
-    let arg2_c = to_cstring(arg2);
-    let arg2_c_ptr = if arg2.is_empty() {
+    let arg2_c = if arg2.is_empty() {
         std::ptr::null()
     } else {
-        arg2_c.as_ptr()
+        to_cstring(arg2) as *const _
     };
 
     match arg0 {
@@ -497,7 +495,7 @@ pub unsafe fn dc_cmdline(context: &Context, line: &str) -> Result<(), failure::E
             ensure!(!arg1.is_empty(), "Argument <file> missing");
             dc_close(context);
             ensure!(
-                0 != dc_open(context, arg1_c_ptr, 0 as *const libc::c_char),
+                0 != dc_open(context, arg1_c, 0 as *const libc::c_char),
                 "Open failed"
             );
         }
@@ -538,7 +536,7 @@ pub unsafe fn dc_cmdline(context: &Context, line: &str) -> Result<(), failure::E
                 !arg1.is_empty() && !arg2.is_empty(),
                 "Arguments <msg-id> <setup-code> expected"
             );
-            if 0 == dc_continue_key_transfer(context, arg1.parse().unwrap(), arg2_c_ptr) {
+            if 0 == dc_continue_key_transfer(context, arg1.parse().unwrap(), arg2_c) {
                 bail!("Continue key transfer failed");
             }
         }
@@ -553,7 +551,7 @@ pub unsafe fn dc_cmdline(context: &Context, line: &str) -> Result<(), failure::E
         }
         "import-backup" => {
             ensure!(!arg1.is_empty(), "Argument <backup-file> missing.");
-            dc_imex(context, 12, arg1_c_ptr, 0 as *const libc::c_char);
+            dc_imex(context, 12, arg1_c, 0 as *const libc::c_char);
         }
         "export-keys" => {
             dc_imex(context, 1, context.get_blobdir(), 0 as *const libc::c_char);
@@ -590,7 +588,7 @@ pub unsafe fn dc_cmdline(context: &Context, line: &str) -> Result<(), failure::E
             free(setup_code as *mut libc::c_void);
         }
         "poke" => {
-            ensure!(0 != poke_spec(context, arg1_c_ptr), "Poke failed");
+            ensure!(0 != poke_spec(context, arg1_c), "Poke failed");
         }
         "reset" => {
             ensure!(!arg1.is_empty(), "Argument <bits> missing: 1=jobs, 2=peerstates, 4=private keys, 8=rest but server config");
@@ -624,7 +622,7 @@ pub unsafe fn dc_cmdline(context: &Context, line: &str) -> Result<(), failure::E
         }
         "listchats" | "listarchived" | "chats" => {
             let listflags = if arg0 == "listarchived" { 0x01 } else { 0 };
-            let chatlist = dc_get_chatlist(context, listflags, arg1_c_ptr, 0 as uint32_t);
+            let chatlist = dc_get_chatlist(context, listflags, arg1_c, 0 as uint32_t);
             ensure!(!chatlist.is_null(), "Failed to retrieve chatlist");
 
             let mut i: libc::c_int;
@@ -782,8 +780,7 @@ pub unsafe fn dc_cmdline(context: &Context, line: &str) -> Result<(), failure::E
         }
         "creategroup" => {
             ensure!(!arg1.is_empty(), "Argument <name> missing.");
-            let chat_id_1: libc::c_int =
-                dc_create_group_chat(context, 0, arg1_c_ptr) as libc::c_int;
+            let chat_id_1: libc::c_int = dc_create_group_chat(context, 0, arg1_c) as libc::c_int;
             if chat_id_1 != 0 {
                 println!("Group#{} created successfully.", chat_id_1,);
             } else {
@@ -792,8 +789,7 @@ pub unsafe fn dc_cmdline(context: &Context, line: &str) -> Result<(), failure::E
         }
         "createverified" => {
             ensure!(!arg1.is_empty(), "Argument <name> missing.");
-            let chat_id_2: libc::c_int =
-                dc_create_group_chat(context, 1, arg1_c_ptr) as libc::c_int;
+            let chat_id_2: libc::c_int = dc_create_group_chat(context, 1, arg1_c) as libc::c_int;
             if chat_id_2 != 0 {
                 println!("VerifiedGroup#{} created successfully.", chat_id_2,);
             } else {
@@ -832,7 +828,7 @@ pub unsafe fn dc_cmdline(context: &Context, line: &str) -> Result<(), failure::E
         "groupname" => {
             ensure!(!sel_chat.is_null(), "No chat selected.");
             ensure!(!arg1.is_empty(), "Argument <name> missing.");
-            if 0 != dc_set_chat_name(context, dc_chat_get_id(sel_chat), arg1_c_ptr) {
+            if 0 != dc_set_chat_name(context, dc_chat_get_id(sel_chat), arg1_c) {
                 println!("Chat name set");
             } else {
                 bail!("Failed to set chat name");
@@ -846,7 +842,7 @@ pub unsafe fn dc_cmdline(context: &Context, line: &str) -> Result<(), failure::E
                 context,
                 dc_chat_get_id(sel_chat),
                 if !arg1.is_empty() {
-                    arg1_c_ptr
+                    arg1_c
                 } else {
                     std::ptr::null_mut()
                 },
@@ -937,9 +933,11 @@ pub unsafe fn dc_cmdline(context: &Context, line: &str) -> Result<(), failure::E
 
             let msg = to_cstring(format!("{} {}", arg1, arg2));
 
-            if 0 != dc_send_text_msg(context, dc_chat_get_id(sel_chat), msg.as_ptr()) {
+            if 0 != dc_send_text_msg(context, dc_chat_get_id(sel_chat), msg) {
                 println!("Message sent.");
+                free(msg as *mut _);
             } else {
+                free(msg as *mut _);
                 bail!("Sending failed.");
             }
         }
@@ -960,8 +958,8 @@ pub unsafe fn dc_cmdline(context: &Context, line: &str) -> Result<(), failure::E
             ensure!(!arg1.is_empty() && !arg2.is_empty(), "No file given.");
 
             let msg_0 = dc_msg_new(context, if arg0 == "sendimage" { 20 } else { 60 });
-            dc_msg_set_file(msg_0, arg1_c_ptr, 0 as *const libc::c_char);
-            dc_msg_set_text(msg_0, arg2_c_ptr);
+            dc_msg_set_file(msg_0, arg1_c, 0 as *const libc::c_char);
+            dc_msg_set_text(msg_0, arg2_c);
             dc_send_msg(context, dc_chat_get_id(sel_chat), msg_0);
             dc_msg_unref(msg_0);
         }
@@ -974,7 +972,7 @@ pub unsafe fn dc_cmdline(context: &Context, line: &str) -> Result<(), failure::E
                 0 as libc::c_uint
             };
 
-            let msglist_0 = dc_search_msgs(context, chat, arg1_c_ptr);
+            let msglist_0 = dc_search_msgs(context, chat, arg1_c);
 
             if !msglist_0.is_null() {
                 log_msglist(context, msglist_0);
@@ -987,7 +985,7 @@ pub unsafe fn dc_cmdline(context: &Context, line: &str) -> Result<(), failure::E
 
             if !arg1.is_empty() {
                 let draft_0 = dc_msg_new(context, 10);
-                dc_msg_set_text(draft_0, arg1_c_ptr);
+                dc_msg_set_text(draft_0, arg1_c);
                 dc_set_draft(context, dc_chat_get_id(sel_chat), draft_0);
                 dc_msg_unref(draft_0);
                 println!("Draft saved.");
@@ -1079,7 +1077,7 @@ pub unsafe fn dc_cmdline(context: &Context, line: &str) -> Result<(), failure::E
                 } else {
                     0x2
                 },
-                arg1_c_ptr,
+                arg1_c,
             );
             if !contacts.is_null() {
                 log_contactlist(context, contacts);
@@ -1095,13 +1093,13 @@ pub unsafe fn dc_cmdline(context: &Context, line: &str) -> Result<(), failure::E
             if !arg2.is_empty() {
                 let book = dc_mprintf(
                     b"%s\n%s\x00" as *const u8 as *const libc::c_char,
-                    arg1_c_ptr,
-                    arg2_c_ptr,
+                    arg1_c,
+                    arg2_c,
                 );
                 dc_add_address_book(context, book);
                 free(book as *mut libc::c_void);
             } else {
-                if 0 == dc_create_contact(context, 0 as *const libc::c_char, arg1_c_ptr) {
+                if 0 == dc_create_contact(context, 0 as *const libc::c_char, arg1_c) {
                     bail!("Failed to create contact");
                 }
             }
@@ -1148,7 +1146,7 @@ pub unsafe fn dc_cmdline(context: &Context, line: &str) -> Result<(), failure::E
         }
         "checkqr" => {
             ensure!(!arg1.is_empty(), "Argument <qr-content> missing.");
-            let res = dc_check_qr(context, arg1_c_ptr);
+            let res = dc_check_qr(context, arg1_c);
             println!(
                 "state={}, id={}, text1={}, text2={}",
                 (*res).state as libc::c_int,
@@ -1176,7 +1174,7 @@ pub unsafe fn dc_cmdline(context: &Context, line: &str) -> Result<(), failure::E
 
             if 0 != dc_read_file(
                 context,
-                arg1_c_ptr,
+                arg1_c,
                 &mut buf as *mut *mut libc::c_uchar as *mut *mut libc::c_void,
                 &mut buf_bytes,
             ) {
@@ -1194,5 +1192,8 @@ pub unsafe fn dc_cmdline(context: &Context, line: &str) -> Result<(), failure::E
         dc_chat_unref(sel_chat);
     }
 
+    free(arg1_c as *mut _);
+    free(arg2_c as *mut _);
+
     Ok(())
 }
diff --git a/examples/repl/main.rs b/examples/repl/main.rs
index ea57e2d02..28f923c3f 100644
--- a/examples/repl/main.rs
+++ b/examples/repl/main.rs
@@ -398,11 +398,10 @@ fn main_0(args: Vec<String>) -> Result<(), failure::Error> {
 
     if args.len() == 2 {
         if 0 == unsafe {
-            dc_open(
-                &mut context,
-                to_cstring(&args[1]).as_ptr(),
-                0 as *const libc::c_char,
-            )
+            let a = to_cstring(&args[1]);
+            let res = dc_open(&mut context, a, 0 as *const _);
+            free(a as *mut _);
+            res
         } {
             println!("Error: Cannot open {}.", args[0],);
         }
@@ -482,11 +481,10 @@ unsafe fn handle_cmd(line: &str, ctx: Arc<RwLock<Context>>) -> Result<ExitResult
     let mut args = line.splitn(2, ' ');
     let arg0 = args.next().unwrap_or_default();
     let arg1 = args.next().unwrap_or_default();
-    let arg1_c = to_cstring(arg1);
-    let arg1_c_ptr = if arg1.is_empty() {
+    let arg1_c = if arg1.is_empty() {
         std::ptr::null()
     } else {
-        arg1_c.as_ptr()
+        to_cstring(arg1)
     };
 
     match arg0 {
@@ -559,13 +557,15 @@ unsafe fn handle_cmd(line: &str, ctx: Arc<RwLock<Context>>) -> Result<ExitResult
         "joinqr" => {
             start_threads(ctx.clone());
             if !arg0.is_empty() {
-                dc_join_securejoin(&ctx.read().unwrap(), arg1_c_ptr);
+                dc_join_securejoin(&ctx.read().unwrap(), arg1_c);
             }
         }
         "exit" => return Ok(ExitResult::Exit),
         _ => dc_cmdline(&ctx.read().unwrap(), line)?,
     }
 
+    free(arg1_c as *mut _);
+
     Ok(ExitResult::Continue)
 }
 
diff --git a/src/config.rs b/src/config.rs
index b5a2e65a4..e2b76be6f 100644
--- a/src/config.rs
+++ b/src/config.rs
@@ -71,7 +71,12 @@ impl Context {
             Config::Selfavatar => {
                 let rel_path = self.sql.get_config(self, key);
                 rel_path.map(|p| {
-                    let v = unsafe { dc_get_abs_path(self, to_cstring(p).as_ptr()) };
+                    let v = unsafe {
+                        let n = to_cstring(p);
+                        let res = dc_get_abs_path(self, n);
+                        free(n as *mut libc::c_void);
+                        res
+                    };
                     let r = to_string(v);
                     unsafe { free(v as *mut _) };
                     r
diff --git a/src/context.rs b/src/context.rs
index fae975717..cd64e1883 100644
--- a/src/context.rs
+++ b/src/context.rs
@@ -279,7 +279,7 @@ unsafe fn cb_get_config(
         .sql
         .get_config(context, as_str(key))
         .unwrap_or_else(|| to_string(def));
-    strdup(to_cstring(res).as_ptr())
+    to_cstring(res)
 }
 
 pub unsafe fn dc_context_unref(context: &mut Context) {
@@ -515,7 +515,7 @@ pub unsafe fn dc_get_info(context: &Context) -> *mut libc::c_char {
         fingerprint_str,
     );
 
-    strdup(to_cstring(res).as_ptr())
+    to_cstring(res)
 }
 
 pub unsafe fn dc_get_version_str() -> *mut libc::c_char {
diff --git a/src/dc_array.rs b/src/dc_array.rs
index be10d86ec..2a44f9ed6 100644
--- a/src/dc_array.rs
+++ b/src/dc_array.rs
@@ -374,7 +374,7 @@ pub unsafe fn dc_array_get_string(
             }
             res
         });
-    strdup(to_cstring(res).as_ptr())
+    to_cstring(res)
 }
 
 /// return comma-separated value-string from integer array
@@ -396,7 +396,7 @@ pub unsafe fn dc_arr_to_string(arr: *const uint32_t, cnt: libc::c_int) -> *mut l
             res
         },
     );
-    strdup(to_cstring(res).as_ptr())
+    to_cstring(res)
 }
 
 #[cfg(test)]
diff --git a/src/dc_chat.rs b/src/dc_chat.rs
index 0438a601b..5e2154507 100644
--- a/src/dc_chat.rs
+++ b/src/dc_chat.rs
@@ -130,15 +130,19 @@ pub fn dc_chat_load_from_db(chat: *mut Chat, chat_id: u32) -> bool {
             c.type_0 = row.get(1)?;
             c.name = {
                 let raw: String = row.get(2)?;
-                unsafe { strdup(to_cstring(raw).as_ptr()) }
+                unsafe { to_cstring(raw) }
             };
             c.grpid = {
                 let raw: String = row.get(3)?;
-                unsafe { strdup(to_cstring(raw).as_ptr()) }
+                unsafe { to_cstring(raw) }
             };
 
             let packed: String = row.get(4)?;
-            unsafe { dc_param_set_packed((*chat).param, to_cstring(&packed).as_ptr()) };
+            unsafe {
+                let p = to_cstring(&packed);
+                dc_param_set_packed((*chat).param, p);
+                free(p as *mut _);
+            };
             c.archived = row.get(5)?;
             c.blocked = row.get(6)?;
             c.gossiped_timestamp = row.get(7)?;
@@ -496,8 +500,9 @@ unsafe fn prepare_msg_raw(
                 } else {
                     0 as *mut libc::c_char
                 },
-                from_c.as_ptr(),
+                from_c,
             );
+            free(from_c as *mut _);
 
             if (*chat).type_0 == 100 {
                 if let Some(id) = context.sql.query_row_col(
@@ -761,9 +766,9 @@ unsafe fn get_parent_mime_headers(
                  FROM msgs WHERE chat_id=? AND from_id!=?);",
                 params![(*chat).id as i32, 1],
                 |row| {
-                    *parent_rfc724_mid = dc_strdup(to_cstring(row.get::<_, String>(0)?).as_ptr());
-                    *parent_in_reply_to = dc_strdup(to_cstring(row.get::<_, String>(1)?).as_ptr());
-                    *parent_references = dc_strdup(to_cstring(row.get::<_, String>(2)?).as_ptr());
+                    *parent_rfc724_mid = to_cstring(row.get::<_, String>(0)?);
+                    *parent_in_reply_to = to_cstring(row.get::<_, String>(1)?);
+                    *parent_references = to_cstring(row.get::<_, String>(2)?);
                     Ok(())
                 },
             )
@@ -779,12 +784,9 @@ unsafe fn get_parent_mime_headers(
                      FROM msgs WHERE chat_id=? AND from_id==?);",
                     params![(*chat).id as i32, 1],
                     |row| {
-                        *parent_rfc724_mid =
-                            dc_strdup(to_cstring(row.get::<_, String>(0)?).as_ptr());
-                        *parent_in_reply_to =
-                            dc_strdup(to_cstring(row.get::<_, String>(1)?).as_ptr());
-                        *parent_references =
-                            dc_strdup(to_cstring(row.get::<_, String>(2)?).as_ptr());
+                        *parent_rfc724_mid = to_cstring(row.get::<_, String>(0)?);
+                        *parent_in_reply_to = to_cstring(row.get::<_, String>(1)?);
+                        *parent_references = to_cstring(row.get::<_, String>(2)?);
                         Ok(())
                     },
                 )
@@ -823,7 +825,8 @@ unsafe fn last_msg_in_chat_encrypted(
     if let Some(packed) = packed {
         let msg_param = dc_param_new();
         let packed_c = to_cstring(packed);
-        dc_param_set_packed(msg_param, packed_c.as_ptr());
+        dc_param_set_packed(msg_param, packed_c);
+        free(packed_c as *mut _);
 
         if 0 != dc_param_exists(msg_param, 'c' as i32) {
             last_is_encrypted = 1;
@@ -2090,7 +2093,7 @@ pub unsafe fn dc_chat_get_subtitle(chat: *const Chat) -> *mut libc::c_char {
                 0,
             )
             .unwrap_or_else(|| "Err".into());
-        ret = dc_strdup(to_cstring(ret_raw).as_ptr());
+        ret = to_cstring(ret_raw);
     } else if (*chat).type_0 == 120 || (*chat).type_0 == 130 {
         if (*chat).id == 1 {
             ret = dc_stock_str((*chat).context, 8)
diff --git a/src/dc_configure.rs b/src/dc_configure.rs
index 33f8e17af..afe339383 100644
--- a/src/dc_configure.rs
+++ b/src/dc_configure.rs
@@ -1098,12 +1098,14 @@ unsafe fn moz_autoconfigure(
         tag_config: 0,
     };
 
-    let xml_raw = read_autoconf_file(context, to_cstring(url).as_ptr());
+    let url_c = to_cstring(url);
+    let xml_raw = read_autoconf_file(context, url_c);
+    free(url_c as *mut libc::c_void);
     if xml_raw.is_null() {
         return None;
     }
 
-    moz_ac.in_emaillocalpart = dc_strdup(to_cstring(&param_in.addr).as_ptr());
+    moz_ac.in_emaillocalpart = to_cstring(&param_in.addr);
     let p = strchr(moz_ac.in_emaillocalpart, '@' as i32);
 
     if p.is_null() {
@@ -1160,11 +1162,13 @@ unsafe fn moz_autoconfigure_text_cb(
     let mut moz_ac: *mut moz_autoconfigure_t = userdata as *mut moz_autoconfigure_t;
     let mut val: *mut libc::c_char = dc_strdup(text);
     dc_trim(val);
+    let addr = to_cstring(&(*moz_ac).in_0.addr);
     dc_str_replace(
         &mut val,
         b"%EMAILADDRESS%\x00" as *const u8 as *const libc::c_char,
-        to_cstring(&(*moz_ac).in_0.addr).as_ptr(),
+        addr,
     );
+    free(addr as *mut libc::c_void);
     dc_str_replace(
         &mut val,
         b"%EMAILLOCALPART%\x00" as *const u8 as *const libc::c_char,
@@ -1298,7 +1302,7 @@ fn read_autoconf_file(context: &Context, url: *const libc::c_char) -> *mut libc:
         .send()
         .and_then(|mut res| res.text())
     {
-        Ok(res) => unsafe { libc::strdup(to_cstring(res).as_ptr()) },
+        Ok(res) => unsafe { to_cstring(res) },
         Err(_err) => {
             info!(context, 0, "Can\'t read file.",);
 
@@ -1314,7 +1318,7 @@ unsafe fn outlk_autodiscover(
 ) -> Option<dc_loginparam_t> {
     let current_block: u64;
     let mut xml_raw: *mut libc::c_char = 0 as *mut libc::c_char;
-    let mut url = dc_strdup(to_cstring(url__).as_ptr());
+    let mut url = to_cstring(url__);
     let mut outlk_ad = outlk_autodiscover_t {
         in_0: param_in,
         out: dc_loginparam_new(),
diff --git a/src/dc_contact.rs b/src/dc_contact.rs
index e35a40eb4..d66e5547a 100644
--- a/src/dc_contact.rs
+++ b/src/dc_contact.rs
@@ -277,15 +277,12 @@ pub unsafe fn dc_contact_load_from_db(
     if contact_id == 1 as libc::c_uint {
         (*contact).id = contact_id;
         (*contact).name = dc_stock_str((*contact).context, 2);
-        (*contact).addr = dc_strdup(
-            to_cstring(
-                (*contact)
-                    .context
-                    .sql
-                    .get_config((*contact).context, "configured_addr")
-                    .unwrap_or_default(),
-            )
-            .as_ptr(),
+        (*contact).addr = to_cstring(
+            (*contact)
+                .context
+                .sql
+                .get_config((*contact).context, "configured_addr")
+                .unwrap_or_default(),
         );
         true
     } else {
@@ -294,11 +291,11 @@ pub unsafe fn dc_contact_load_from_db(
             params![contact_id as i32],
             |row| {
                 (*contact).id = contact_id;
-                (*contact).name = dc_strdup(to_cstring(row.get::<_, String>(0)?).as_ptr());
-                (*contact).addr = dc_strdup(to_cstring(row.get::<_, String>(1)?).as_ptr());
+                (*contact).name = to_cstring(row.get::<_, String>(0)?);
+                (*contact).addr = to_cstring(row.get::<_, String>(1)?);
                 (*contact).origin = row.get(2)?;
                 (*contact).blocked = row.get(3)?;
-                (*contact).authname = dc_strdup(to_cstring(row.get::<_, String>(4)?).as_ptr());
+                (*contact).authname = to_cstring(row.get::<_, String>(4)?);
                 Ok(())
             }
         ).is_ok()
@@ -735,7 +732,7 @@ pub unsafe fn dc_get_contact_encrinfo(
     free(fingerprint_other_verified as *mut libc::c_void);
     free(fingerprint_other_unverified as *mut libc::c_void);
 
-    strdup(to_cstring(ret).as_ptr())
+    to_cstring(ret)
 }
 
 unsafe fn cat_fingerprint(
@@ -905,7 +902,7 @@ pub fn dc_contact_get_profile_image(contact: *const dc_contact_t) -> *mut libc::
     if unsafe { (*contact).id } == 1 {
         let context = unsafe { (*contact) }.context;
         if let Some(avatar) = context.get_config(config::Config::Selfavatar) {
-            image_abs = unsafe { dc_strdup(to_cstring(avatar).as_ptr()) };
+            image_abs = unsafe { to_cstring(avatar) };
         }
     }
     // TODO: else get image_abs from contact param
diff --git a/src/dc_dehtml.rs b/src/dc_dehtml.rs
index 805ea5c6b..ae0cd7546 100644
--- a/src/dc_dehtml.rs
+++ b/src/dc_dehtml.rs
@@ -53,7 +53,7 @@ pub unsafe fn dc_dehtml(buf_terminated: *mut libc::c_char) -> *mut libc::c_char
     dc_saxparser_parse(&mut saxparser, buf_terminated);
     free(dehtml.last_href as *mut libc::c_void);
 
-    strdup(to_cstring(dehtml.strbuilder).as_ptr())
+    to_cstring(dehtml.strbuilder)
 }
 
 unsafe fn dehtml_text_cb(
diff --git a/src/dc_e2ee.rs b/src/dc_e2ee.rs
index 3cf4569bb..11714e2c6 100644
--- a/src/dc_e2ee.rs
+++ b/src/dc_e2ee.rs
@@ -184,7 +184,7 @@ pub unsafe fn dc_e2ee_encrypt(
                                                     b"Autocrypt-Gossip\x00" as *const u8
                                                         as *const libc::c_char,
                                                 ),
-                                                strdup(header.as_ptr()),
+                                                header,
                                             ),
                                         );
                                     }
diff --git a/src/dc_imex.rs b/src/dc_imex.rs
index c70a4b65d..2d9de702d 100644
--- a/src/dc_imex.rs
+++ b/src/dc_imex.rs
@@ -309,7 +309,7 @@ pub unsafe fn dc_create_setup_code(_context: &Context) -> *mut libc::c_char {
         );
     }
 
-    strdup(to_cstring(ret).as_ptr())
+    to_cstring(ret)
 }
 
 // TODO should return bool /rtn
@@ -539,7 +539,7 @@ pub unsafe fn dc_normalize_setup_code(
         p1 = p1.offset(1);
     }
 
-    strdup(to_cstring(out).as_ptr())
+    to_cstring(out)
 }
 
 pub unsafe fn dc_job_do_DC_JOB_IMEX_IMAP(context: &Context, job: *mut dc_job_t) {
@@ -895,7 +895,8 @@ unsafe fn export_backup(context: &Context, dir: *const libc::c_char) -> libc::c_
         .format("delta-chat-%Y-%m-%d.bak")
         .to_string();
     let buffer = to_cstring(res);
-    let dest_pathNfilename = dc_get_fine_pathNfilename(context, dir, buffer.as_ptr());
+    let dest_pathNfilename = dc_get_fine_pathNfilename(context, dir, buffer);
+    free(buffer as *mut _);
     if dest_pathNfilename.is_null() {
         error!(context, 0, "Cannot get backup file name.",);
 
@@ -1094,6 +1095,7 @@ unsafe fn import_self_keys(context: &Context, dir_name: *const libc::c_char) ->
     let mut imported_cnt: libc::c_int = 0;
     let mut suffix: *mut libc::c_char = 0 as *mut libc::c_char;
     let mut path_plus_name: *mut libc::c_char = 0 as *mut libc::c_char;
+    let mut name_c: *mut libc::c_char = 0 as *mut libc::c_char;
     let mut set_default: libc::c_int;
     let mut buf: *mut libc::c_char = 0 as *mut libc::c_char;
     let mut buf_bytes: size_t = 0 as size_t;
@@ -1121,8 +1123,9 @@ unsafe fn import_self_keys(context: &Context, dir_name: *const libc::c_char) ->
                 let entry = entry.unwrap();
                 free(suffix as *mut libc::c_void);
                 let name_f = entry.file_name();
-                let name_c = to_cstring(name_f.to_string_lossy());
-                suffix = dc_get_filesuffix_lc(name_c.as_ptr());
+                free(name_c as *mut libc::c_void);
+                name_c = to_cstring(name_f.to_string_lossy());
+                suffix = dc_get_filesuffix_lc(name_c);
                 if suffix.is_null()
                     || strcmp(suffix, b"asc\x00" as *const u8 as *const libc::c_char) != 0
                 {
@@ -1132,7 +1135,7 @@ unsafe fn import_self_keys(context: &Context, dir_name: *const libc::c_char) ->
                 path_plus_name = dc_mprintf(
                     b"%s/%s\x00" as *const u8 as *const libc::c_char,
                     dir_name,
-                    name_c.as_ptr(),
+                    name_c,
                 );
                 info!(context, 0, "Checking: {}", as_str(path_plus_name));
                 free(buf as *mut libc::c_void);
@@ -1170,12 +1173,7 @@ unsafe fn import_self_keys(context: &Context, dir_name: *const libc::c_char) ->
                     }
                 }
                 set_default = 1;
-                if !strstr(
-                    name_c.as_ptr(),
-                    b"legacy\x00" as *const u8 as *const libc::c_char,
-                )
-                .is_null()
-                {
+                if !strstr(name_c, b"legacy\x00" as *const u8 as *const libc::c_char).is_null() {
                     info!(
                         context,
                         0,
@@ -1200,6 +1198,7 @@ unsafe fn import_self_keys(context: &Context, dir_name: *const libc::c_char) ->
         }
     }
 
+    free(name_c as *mut libc::c_void);
     free(suffix as *mut libc::c_void);
     free(path_plus_name as *mut libc::c_void);
     free(buf as *mut libc::c_void);
diff --git a/src/dc_job.rs b/src/dc_job.rs
index ce3a23e34..f93eb673f 100644
--- a/src/dc_job.rs
+++ b/src/dc_job.rs
@@ -99,7 +99,9 @@ unsafe fn dc_job_perform(context: &Context, thread: libc::c_int, probe_network:
             };
 
             let packed: String = row.get(3)?;
-            dc_param_set_packed(job.param, to_cstring(packed).as_ptr());
+            let packed_c = to_cstring(packed);
+            dc_param_set_packed(job.param, packed_c);
+            free(packed_c as *mut _);
             info!(context, 0, "DONE jobs query_maps row");
             Ok(job)
         },
diff --git a/src/dc_location.rs b/src/dc_location.rs
index 3c7555610..0b030d41f 100644
--- a/src/dc_location.rs
+++ b/src/dc_location.rs
@@ -215,8 +215,10 @@ pub fn dc_get_locations(
                 if 0 != (*loc).msg_id {
                     let txt: String = row.get(9)?;
                     let txt_c = to_cstring(txt);
-                    if 0 != is_marker(txt_c.as_ptr()) {
-                        (*loc).marker = strdup(txt_c.as_ptr());
+                    if 0 != is_marker(txt_c) {
+                        (*loc).marker = txt_c;
+                    } else {
+                        free(txt_c as *mut _);
                     }
                 }
                 Ok(loc)
@@ -330,9 +332,9 @@ pub fn dc_get_location_kml(
     }
 
     if 0 != success {
-        unsafe { strdup(to_cstring(ret).as_ptr()) }
+        unsafe { to_cstring(ret) }
     } else {
-        0 as *mut libc::c_char
+        std::ptr::null_mut()
     }
 }
 
@@ -344,7 +346,7 @@ unsafe fn get_kml_timestamp(utc: i64) -> *mut libc::c_char {
     let res = chrono::NaiveDateTime::from_timestamp(utc, 0)
         .format("%Y-%m-%dT%H:%M:%SZ")
         .to_string();
-    strdup(to_cstring(res).as_ptr())
+    to_cstring(res)
 }
 
 pub unsafe fn dc_get_message_kml(
diff --git a/src/dc_mimefactory.rs b/src/dc_mimefactory.rs
index d1eb9dcc7..0eb68bd67 100644
--- a/src/dc_mimefactory.rs
+++ b/src/dc_mimefactory.rs
@@ -161,24 +161,20 @@ pub unsafe fn dc_mimefactory_load_msg(
                         for row in rows {
                             let (authname, addr) = row?;
                             let addr_c = to_cstring(addr);
-                            if clist_search_string_nocase(
-                                (*factory).recipients_addr,
-                                addr_c.as_ptr(),
-                            ) == 0
-                            {
+                            if clist_search_string_nocase((*factory).recipients_addr, addr_c) == 0 {
                                 clist_insert_after(
                                     (*factory).recipients_names,
                                     (*(*factory).recipients_names).last,
                                     if !authname.is_empty() {
-                                        dc_strdup(to_cstring(authname).as_ptr())
+                                        to_cstring(authname)
                                     } else {
-                                        0 as *mut libc::c_char
+                                        std::ptr::null_mut()
                                     } as *mut libc::c_void,
                                 );
                                 clist_insert_after(
                                     (*factory).recipients_addr,
                                     (*(*factory).recipients_addr).last,
-                                    dc_strdup(addr_c.as_ptr()) as *mut libc::c_void,
+                                    addr_c as *mut libc::c_void,
                                 );
                             }
                         }
@@ -241,8 +237,8 @@ pub unsafe fn dc_mimefactory_load_msg(
         );
         match row {
             Ok((in_reply_to, references)) => {
-                (*factory).in_reply_to = dc_strdup(to_cstring(in_reply_to).as_ptr());
-                (*factory).references = dc_strdup(to_cstring(references).as_ptr());
+                (*factory).in_reply_to = to_cstring(in_reply_to);
+                (*factory).references = to_cstring(references);
             }
             Err(err) => {
                 error!(
@@ -266,32 +262,24 @@ pub unsafe fn dc_mimefactory_load_msg(
 
 unsafe fn load_from(mut factory: *mut dc_mimefactory_t) {
     let context = (*factory).context;
-    (*factory).from_addr = strdup(
-        to_cstring(
-            context
-                .sql
-                .get_config(context, "configured_addr")
-                .unwrap_or_default(),
-        )
-        .as_ptr(),
+    (*factory).from_addr = to_cstring(
+        context
+            .sql
+            .get_config(context, "configured_addr")
+            .unwrap_or_default(),
     );
-    (*factory).from_displayname = strdup(
-        to_cstring(
-            context
-                .sql
-                .get_config(context, "displayname")
-                .unwrap_or_default(),
-        )
-        .as_ptr(),
+
+    (*factory).from_displayname = to_cstring(
+        context
+            .sql
+            .get_config(context, "displayname")
+            .unwrap_or_default(),
     );
-    (*factory).selfstatus = strdup(
-        to_cstring(
-            context
-                .sql
-                .get_config(context, "selfstatus")
-                .unwrap_or_default(),
-        )
-        .as_ptr(),
+    (*factory).selfstatus = to_cstring(
+        context
+            .sql
+            .get_config(context, "selfstatus")
+            .unwrap_or_default(),
     );
     if (*factory).selfstatus.is_null() {
         (*factory).selfstatus = dc_stock_str((*factory).context, 13)
@@ -1178,7 +1166,7 @@ unsafe fn build_body_file(
             let res = ts
                 .format(&format!("voice-message_%Y-%m-%d_%H-%M-%S.{}", suffix))
                 .to_string();
-            filename_to_send = strdup(to_cstring(res).as_ptr());
+            filename_to_send = to_cstring(res);
         } else if (*msg).type_0 == 40 {
             filename_to_send = dc_get_filename(pathNfilename)
         } else if (*msg).type_0 == 20 || (*msg).type_0 == 21 {
diff --git a/src/dc_mimeparser.rs b/src/dc_mimeparser.rs
index d6d57afb5..6efb993b9 100644
--- a/src/dc_mimeparser.rs
+++ b/src/dc_mimeparser.rs
@@ -1341,8 +1341,9 @@ unsafe fn dc_mimeparser_add_single_part_if_known(
                         }
                         if !filename_parts.is_empty() {
                             free(desired_filename as *mut libc::c_void);
-                            desired_filename =
-                                dc_decode_ext_header(to_cstring(filename_parts).as_ptr());
+                            let parts_c = to_cstring(filename_parts);
+                            desired_filename = dc_decode_ext_header(parts_c);
+                            free(parts_c as *mut _);
                         }
                         if desired_filename.is_null() {
                             let param = mailmime_find_ct_parameter(
diff --git a/src/dc_msg.rs b/src/dc_msg.rs
index fa5a31419..9d07fa2ad 100644
--- a/src/dc_msg.rs
+++ b/src/dc_msg.rs
@@ -63,7 +63,7 @@ pub unsafe fn dc_get_msg_info(context: &Context, msg_id: u32) -> *mut libc::c_ch
         ret += &format!("Cannot load message #{}.", msg_id as usize);
         dc_msg_unref(msg);
         dc_contact_unref(contact_from);
-        return strdup(to_cstring(ret).as_ptr());
+        return to_cstring(ret);
     }
     let rawtxt = rawtxt.unwrap();
     let rawtxt = dc_truncate_str(rawtxt.trim(), 100000);
@@ -91,7 +91,7 @@ pub unsafe fn dc_get_msg_info(context: &Context, msg_id: u32) -> *mut libc::c_ch
         // device-internal message, no further details needed
         dc_msg_unref(msg);
         dc_contact_unref(contact_from);
-        return strdup(to_cstring(ret).as_ptr());
+        return to_cstring(ret);
     }
 
     context
@@ -209,7 +209,7 @@ pub unsafe fn dc_get_msg_info(context: &Context, msg_id: u32) -> *mut libc::c_ch
 
     dc_msg_unref(msg);
     dc_contact_unref(contact_from);
-    strdup(to_cstring(ret).as_ptr())
+    to_cstring(ret)
 }
 
 pub unsafe fn dc_msg_new_untyped<'a>(context: &'a Context) -> *mut dc_msg_t<'a> {
@@ -445,9 +445,9 @@ pub fn dc_msg_load_from_db<'a>(msg: *mut dc_msg_t<'a>, context: &'a Context, id:
                 dc_msg_empty(msg);
 
                 (*msg).id = row.get::<_, i32>(0)? as u32;
-                (*msg).rfc724_mid = dc_strdup(to_cstring(row.get::<_, String>(1)?).as_ptr());
-                (*msg).in_reply_to = dc_strdup(to_cstring(row.get::<_, String>(2)?).as_ptr());
-                (*msg).server_folder = dc_strdup(to_cstring(row.get::<_, String>(3)?).as_ptr());
+                (*msg).rfc724_mid = to_cstring(row.get::<_, String>(1)?);
+                (*msg).in_reply_to = to_cstring(row.get::<_, String>(2)?);
+                (*msg).server_folder = to_cstring(row.get::<_, String>(3)?);
                 (*msg).server_uid = row.get(4)?;
                 (*msg).move_state = row.get(5)?;
                 (*msg).chat_id = row.get(6)?;
@@ -459,10 +459,10 @@ pub fn dc_msg_load_from_db<'a>(msg: *mut dc_msg_t<'a>, context: &'a Context, id:
                 (*msg).type_0 = row.get(12)?;
                 (*msg).state = row.get(13)?;
                 (*msg).is_dc_message = row.get(14)?;
-                (*msg).text = dc_strdup(to_cstring(row.get::<_, String>(15).unwrap_or_default()).as_ptr());
+                (*msg).text = to_cstring(row.get::<_, String>(15).unwrap_or_default());
                 dc_param_set_packed(
                     (*msg).param,
-                    to_cstring(row.get::<_, String>(16)?).as_ptr()
+                    to_cstring(row.get::<_, String>(16)?)
                 );
                 (*msg).starred = row.get(17)?;
                 (*msg).hidden = row.get(18)?;
@@ -494,7 +494,10 @@ pub unsafe fn dc_get_mime_headers(context: &Context, msg_id: uint32_t) -> *mut l
     );
 
     if let Some(headers) = headers {
-        dc_strdup_keep_null(to_cstring(headers).as_ptr())
+        let h = to_cstring(headers);
+        let res = dc_strdup_keep_null(h);
+        free(h as *mut _);
+        res
     } else {
         std::ptr::null_mut()
     }
@@ -691,7 +694,7 @@ pub unsafe fn dc_msg_get_text(msg: *const dc_msg_t) -> *mut libc::c_char {
     }
 
     let res = dc_truncate_str(as_str((*msg).text), 30000);
-    dc_strdup(to_cstring(res).as_ptr())
+    to_cstring(res)
 }
 
 pub unsafe fn dc_msg_get_filename(msg: *const dc_msg_t) -> *mut libc::c_char {
@@ -1357,9 +1360,7 @@ pub fn dc_rfc724_mid_exists(
         &[as_str(rfc724_mid)],
         |row| {
             if !ret_server_folder.is_null() {
-                unsafe {
-                    *ret_server_folder = dc_strdup(to_cstring(row.get::<_, String>(0)?).as_ptr())
-                };
+                unsafe { *ret_server_folder = to_cstring(row.get::<_, String>(0)?) };
             }
             if !ret_server_uid.is_null() {
                 unsafe { *ret_server_uid = row.get(1)? };
diff --git a/src/dc_qr.rs b/src/dc_qr.rs
index 1b72ab2d6..e6ff634e7 100644
--- a/src/dc_qr.rs
+++ b/src/dc_qr.rs
@@ -239,13 +239,8 @@ pub unsafe fn dc_check_qr(context: &Context, qr: *const libc::c_char) -> *mut dc
                                     if addr.is_null() || invitenumber.is_null() || auth.is_null() {
                                         if let Some(peerstate) = peerstate {
                                             (*qr_parsed).state = 210i32;
-                                            let c_addr = peerstate
-                                                .addr
-                                                .as_ref()
-                                                .map(to_cstring)
-                                                .unwrap_or_default();
-                                            let addr_ptr = if peerstate.addr.is_some() {
-                                                c_addr.as_ptr()
+                                            let addr_ptr = if let Some(ref addr) = peerstate.addr {
+                                                to_cstring(addr)
                                             } else {
                                                 std::ptr::null()
                                             };
@@ -256,6 +251,7 @@ pub unsafe fn dc_check_qr(context: &Context, qr: *const libc::c_char) -> *mut dc
                                                 0x80i32,
                                                 0 as *mut libc::c_int,
                                             );
+                                            free(addr_ptr as *mut _);
                                             dc_create_or_lookup_nchat_by_contact_id(
                                                 context,
                                                 (*qr_parsed).id,
diff --git a/src/dc_receive_imf.rs b/src/dc_receive_imf.rs
index ff95417de..78825d9d1 100644
--- a/src/dc_receive_imf.rs
+++ b/src/dc_receive_imf.rs
@@ -739,11 +739,9 @@ pub unsafe fn dc_receive_imf(
                                 }
                                 if 0 != mime_parser.is_send_by_messenger || 0 != mdn_consumed {
                                     let param = dc_param_new();
-                                    dc_param_set(
-                                        param,
-                                        'Z' as i32,
-                                        to_cstring(server_folder.as_ref()).as_ptr(),
-                                    );
+                                    let server_folder_c = to_cstring(server_folder.as_ref());
+                                    dc_param_set(param, 'Z' as i32, server_folder_c);
+                                    free(server_folder_c as *mut _);
                                     dc_param_set_int(param, 'z' as i32, server_uid as i32);
                                     if 0 != mime_parser.is_send_by_messenger
                                         && 0 != context
@@ -1518,9 +1516,7 @@ fn hex_hash(s: impl AsRef<str>) -> *const libc::c_char {
     let bytes = s.as_ref().as_bytes();
     let result = Sha256::digest(bytes);
     let result_hex = hex::encode(&result[..8]);
-    let result_cstring = to_cstring(result_hex);
-
-    unsafe { strdup(result_cstring.as_ptr()) }
+    unsafe { to_cstring(result_hex) as *const _ }
 }
 
 unsafe fn search_chat_ids_by_contact_ids(
@@ -1604,8 +1600,7 @@ unsafe fn check_verified_properties(
     let contact = dc_contact_new(context);
 
     let verify_fail = |reason: String| {
-        *failure_reason =
-            strdup(to_cstring(format!("{}. See \"Info\" for details.", reason)).as_ptr());
+        *failure_reason = to_cstring(format!("{}. See \"Info\" for details.", reason));
         warn!(context, 0, "{}", reason);
     };
 
diff --git a/src/dc_securejoin.rs b/src/dc_securejoin.rs
index 07d34637d..af8bacdf7 100644
--- a/src/dc_securejoin.rs
+++ b/src/dc_securejoin.rs
@@ -62,7 +62,7 @@ pub unsafe fn dc_get_securejoin_qr(
         free(group_name_urlencoded as *mut libc::c_void);
 
         if let Some(qr) = qr {
-            strdup(to_cstring(qr).as_ptr())
+            to_cstring(qr)
         } else {
             std::ptr::null_mut()
         }
@@ -939,15 +939,15 @@ pub unsafe fn dc_handle_degrade_event(context: &Context, peerstate: &Peerstate)
                 &mut contact_chat_id,
                 0 as *mut libc::c_int,
             );
-            let c_addr = peerstate.addr.as_ref().map(to_cstring).unwrap_or_default();
-            let c_addr_ptr = if peerstate.addr.is_some() {
-                c_addr.as_ptr()
+            let c_addr_ptr = if let Some(ref addr) = peerstate.addr {
+                to_cstring(addr)
             } else {
                 std::ptr::null_mut()
             };
             let msg = dc_stock_str_repl_string(context, 37, c_addr_ptr);
             dc_add_device_msg(context, contact_chat_id, msg);
             free(msg as *mut libc::c_void);
+            free(c_addr_ptr as *mut _);
             context.call_cb(
                 Event::CHAT_MODIFIED,
                 contact_chat_id as uintptr_t,
diff --git a/src/dc_simplify.rs b/src/dc_simplify.rs
index dcf3aecd2..bf5162300 100644
--- a/src/dc_simplify.rs
+++ b/src/dc_simplify.rs
@@ -238,7 +238,7 @@ unsafe fn dc_simplify_simplify_plain_text(
     }
     dc_free_splitted_lines(lines);
 
-    strdup(to_cstring(ret).as_ptr())
+    to_cstring(ret)
 }
 
 /**
diff --git a/src/dc_strencode.rs b/src/dc_strencode.rs
index bf9b962ef..51501dd87 100644
--- a/src/dc_strencode.rs
+++ b/src/dc_strencode.rs
@@ -712,7 +712,8 @@ unsafe fn print_hex(target: *mut libc::c_char, cur: *const libc::c_char) {
 
     let bytes = std::slice::from_raw_parts(cur as *const _, strlen(cur));
     let raw = to_cstring(format!("={}", &hex::encode_upper(bytes)[..2]));
-    libc::memcpy(target as *mut _, raw.as_ptr() as *const _, 4);
+    libc::memcpy(target as *mut _, raw as *const _, 4);
+    free(raw as *mut libc::c_void);
 }
 
 #[cfg(test)]
diff --git a/src/dc_token.rs b/src/dc_token.rs
index 33583c7ae..ebbe2748e 100644
--- a/src/dc_token.rs
+++ b/src/dc_token.rs
@@ -1,7 +1,6 @@
 use crate::context::Context;
 use crate::dc_tools::*;
 use crate::sql;
-use crate::x::strdup;
 
 // Token namespaces
 pub type dc_tokennamespc_t = usize;
@@ -34,16 +33,16 @@ pub fn dc_token_lookup(
     namespc: dc_tokennamespc_t,
     foreign_id: u32,
 ) -> *mut libc::c_char {
-    if let Some(token) = context.sql.query_row_col::<_, String>(
-        context,
-        "SELECT token FROM tokens WHERE namespc=? AND foreign_id=?;",
-        params![namespc as i32, foreign_id as i32],
-        0,
-    ) {
-        unsafe { strdup(to_cstring(token).as_ptr()) }
-    } else {
-        std::ptr::null_mut()
-    }
+    context
+        .sql
+        .query_row_col::<_, String>(
+            context,
+            "SELECT token FROM tokens WHERE namespc=? AND foreign_id=?;",
+            params![namespc as i32, foreign_id as i32],
+            0,
+        )
+        .map(|s| unsafe { to_cstring(s) })
+        .unwrap_or_else(|| std::ptr::null_mut())
 }
 
 pub fn dc_token_exists(
diff --git a/src/log.rs b/src/log.rs
index 0ea011482..6ab8c4702 100644
--- a/src/log.rs
+++ b/src/log.rs
@@ -3,11 +3,14 @@ macro_rules! info {
     ($ctx:expr, $data1:expr, $msg:expr) => {
         info!($ctx, $data1, $msg,)
     };
-    ($ctx:expr, $data1:expr, $msg:expr, $($args:expr),* $(,)?) => {{
-        let formatted = format!($msg, $($args),*);
-        let formatted_c = $crate::dc_tools::to_cstring(formatted);
-        $ctx.call_cb($crate::constants::Event::INFO, $data1 as libc::uintptr_t,
-                     formatted_c.as_ptr() as libc::uintptr_t)
+    ($ctx:expr, $data1:expr, $msg:expr, $($args:expr),* $(,)?) => {
+        #[allow(unused_unsafe)]
+        unsafe {
+            let formatted = format!($msg, $($args),*);
+            let formatted_c =  $crate::dc_tools::to_cstring(formatted);
+            $ctx.call_cb($crate::constants::Event::INFO, $data1 as libc::uintptr_t,
+                     formatted_c as libc::uintptr_t);
+            libc::free(formatted_c as *mut libc::c_void);
     }};
 }
 
@@ -17,11 +20,14 @@ macro_rules! warn {
         warn!($ctx, $data1, $msg,)
     };
     ($ctx:expr, $data1:expr, $msg:expr, $($args:expr),* $(,)?) => {
-        let formatted = format!($msg, $($args),*);
-        let formatted_c = $crate::dc_tools::to_cstring(formatted);
-        $ctx.call_cb($crate::constants::Event::WARNING, $data1 as libc::uintptr_t,
-                     formatted_c.as_ptr() as libc::uintptr_t)
-    };
+        #[allow(unused_unsafe)]
+        unsafe {
+            let formatted = format!($msg, $($args),*);
+            let formatted_c = $crate::dc_tools::to_cstring(formatted);
+            $ctx.call_cb($crate::constants::Event::WARNING, $data1 as libc::uintptr_t,
+                         formatted_c as libc::uintptr_t);
+            libc::free(formatted_c as *mut libc::c_void) ;
+        }};
 }
 
 #[macro_export]
@@ -30,11 +36,14 @@ macro_rules! error {
         error!($ctx, $data1, $msg,)
     };
     ($ctx:expr, $data1:expr, $msg:expr, $($args:expr),* $(,)?) => {
+        #[allow(unused_unsafe)]
+        unsafe {
         let formatted = format!($msg, $($args),*);
         let formatted_c = $crate::dc_tools::to_cstring(formatted);
         $ctx.call_cb($crate::constants::Event::ERROR, $data1 as libc::uintptr_t,
-                     formatted_c.as_ptr() as libc::uintptr_t)
-    };
+                     formatted_c as libc::uintptr_t);
+        libc::free(formatted_c as *mut libc::c_void);
+    }};
 }
 
 #[macro_export]
@@ -43,9 +52,12 @@ macro_rules! log_event {
         log_event!($ctx, $data1, $msg,)
     };
     ($ctx:expr, $event:expr, $data1:expr, $msg:expr, $($args:expr),* $(,)?) => {
-        let formatted = format!($msg, $($args),*);
-        let formatted_c = $crate::dc_tools::to_cstring(formatted);
-        $ctx.call_cb($event, $data1 as libc::uintptr_t,
-                     formatted_c.as_ptr() as libc::uintptr_t)
-    };
+        #[allow(unused_unsafe)]
+        unsafe {
+            let formatted = format!($msg, $($args),*);
+            let formatted_c = $crate::dc_tools::to_cstring(formatted);
+            $ctx.call_cb($event, $data1 as libc::uintptr_t,
+                         formatted_c as libc::uintptr_t);
+            libc::free(formatted_c as *mut libc::c_void);
+    }};
 }
diff --git a/src/sql.rs b/src/sql.rs
index d63731b19..3fd406171 100644
--- a/src/sql.rs
+++ b/src/sql.rs
@@ -1005,31 +1005,36 @@ pub fn housekeeping(context: &Context) {
                 }
                 let entry = entry.unwrap();
                 let name_f = entry.file_name();
-                let name_c = to_cstring(name_f.to_string_lossy());
+                let name_c = unsafe { to_cstring(name_f.to_string_lossy()) };
 
-                if unsafe {
-                    is_file_in_use(&mut files_in_use, 0 as *const libc::c_char, name_c.as_ptr())
-                } || unsafe {
-                    is_file_in_use(
-                        &mut files_in_use,
-                        b".increation\x00" as *const u8 as *const libc::c_char,
-                        name_c.as_ptr(),
-                    )
-                } || unsafe {
-                    is_file_in_use(
-                        &mut files_in_use,
-                        b".waveform\x00" as *const u8 as *const libc::c_char,
-                        name_c.as_ptr(),
-                    )
-                } || unsafe {
-                    is_file_in_use(
-                        &mut files_in_use,
-                        b"-preview.jpg\x00" as *const u8 as *const libc::c_char,
-                        name_c.as_ptr(),
-                    )
-                } {
+                if unsafe { is_file_in_use(&mut files_in_use, 0 as *const libc::c_char, name_c) }
+                    || unsafe {
+                        is_file_in_use(
+                            &mut files_in_use,
+                            b".increation\x00" as *const u8 as *const libc::c_char,
+                            name_c,
+                        )
+                    }
+                    || unsafe {
+                        is_file_in_use(
+                            &mut files_in_use,
+                            b".waveform\x00" as *const u8 as *const libc::c_char,
+                            name_c,
+                        )
+                    }
+                    || unsafe {
+                        is_file_in_use(
+                            &mut files_in_use,
+                            b"-preview.jpg\x00" as *const u8 as *const libc::c_char,
+                            name_c,
+                        )
+                    }
+                {
+                    unsafe { free(name_c as *mut _) };
                     continue;
                 }
+                unsafe { free(name_c as *mut _) };
+
                 unreferenced_count += 1;
 
                 match std::fs::metadata(entry.path()) {
@@ -1061,8 +1066,11 @@ pub fn housekeeping(context: &Context) {
                     unreferenced_count,
                     entry.file_name()
                 );
-                let path = to_cstring(entry.path().to_str().unwrap());
-                unsafe { dc_delete_file(context, path.as_ptr()) };
+                unsafe {
+                    let path = to_cstring(entry.path().to_str().unwrap());
+                    dc_delete_file(context, path);
+                    free(path as *mut _);
+                }
             }
         }
         Err(err) => {
@@ -1120,14 +1128,16 @@ fn maybe_add_from_param(
     context
         .sql
         .query_row(query, NO_PARAMS, |row| {
-            let v = to_cstring(row.get::<_, String>(0)?);
             unsafe {
-                dc_param_set_packed(param, v.as_ptr() as *const libc::c_char);
-                let file = dc_param_get(param, param_id, 0 as *const libc::c_char);
+                let v = to_cstring(row.get::<_, String>(0)?);
+                dc_param_set_packed(param, v as *const _);
+                let file = dc_param_get(param, param_id, 0 as *const _);
                 if !file.is_null() {
                     maybe_add_file(files_in_use, as_str(file));
                     free(file as *mut libc::c_void);
                 }
+
+                free(v as *mut _);
             }
             Ok(())
         })
diff --git a/tests/stress.rs b/tests/stress.rs
index 1835737e9..b32824ea6 100644
--- a/tests/stress.rs
+++ b/tests/stress.rs
@@ -175,7 +175,7 @@ unsafe fn stress_functions(context: &Context) {
             "content"
         );
 
-        free(buf);
+        free(buf as *mut _);
         assert_ne!(
             0,
             dc_delete_file(
@@ -952,24 +952,29 @@ fn test_stress_tests() {
 fn test_get_contacts() {
     unsafe {
         let context = create_test_context();
-        let contacts = dc_get_contacts(&context.ctx, 0, to_cstring("some2").as_ptr());
+        let name = to_cstring("some2");
+        let contacts = dc_get_contacts(&context.ctx, 0, name);
         assert_eq!(dc_array_get_cnt(contacts), 0);
         dc_array_unref(contacts);
+        free(name as *mut _);
 
-        let id = dc_create_contact(
-            &context.ctx,
-            to_cstring("bob").as_ptr(),
-            to_cstring("bob@mail.de").as_ptr(),
-        );
+        let name = to_cstring("bob");
+        let email = to_cstring("bob@mail.de");
+        let id = dc_create_contact(&context.ctx, name, email);
         assert_ne!(id, 0);
 
-        let contacts = dc_get_contacts(&context.ctx, 0, to_cstring("bob").as_ptr());
+        let contacts = dc_get_contacts(&context.ctx, 0, name);
         assert_eq!(dc_array_get_cnt(contacts), 1);
         dc_array_unref(contacts);
 
-        let contacts = dc_get_contacts(&context.ctx, 0, to_cstring("alice").as_ptr());
+        let name2 = to_cstring("alice");
+        let contacts = dc_get_contacts(&context.ctx, 0, name2);
         assert_eq!(dc_array_get_cnt(contacts), 0);
         dc_array_unref(contacts);
+
+        free(name as *mut _);
+        free(name2 as *mut _);
+        free(email as *mut _);
     }
 }
 
@@ -977,11 +982,12 @@ fn test_get_contacts() {
 fn test_chat() {
     unsafe {
         let context = create_test_context();
-        let contact1 = dc_create_contact(
-            &context.ctx,
-            to_cstring("bob").as_ptr(),
-            to_cstring("bob@mail.de").as_ptr(),
-        );
+        let name = to_cstring("bob");
+        let email = to_cstring("bob@mail.de");
+
+        let contact1 = dc_create_contact(&context.ctx, name, email);
+        free(name as *mut _);
+        free(email as *mut _);
         assert_ne!(contact1, 0);
 
         let chat_id = dc_create_chat_by_contact_id(&context.ctx, contact1);