Fix closure in dc_securejoin, make sure we return an empty string and

never null, make dc_get_securejoin_qr return an Option<String> and move
the logic to cast it to c_str into the ffi

deltachat-ffi/src/lib.rs

@@ -1320,12 +1320,11 @@ pub unsafe extern "C" fn dc_get_securejoin_qr(
 ) -> *mut libc::c_char {
     if context.is_null() {
         eprintln!("ignoring careless call to dc_get_securejoin_qr()");
-        return dc_strdup(ptr::null());
+        "".strdup()
     }
 
     let context = &*context;
-
-    dc_securejoin::dc_get_securejoin_qr(context, chat_id)
+    dc_securejoin::dc_get_securejoin_qr(context, chat_id).unwrap_or("").strdup()
 }
 
 #[no_mangle]

examples/repl/main.rs

@@ -17,6 +17,8 @@ use std::borrow::Cow::{self, Borrowed, Owned};
 use std::ptr;
 use std::sync::atomic::{AtomicBool, Ordering};
 use std::sync::{Arc, Mutex, RwLock};
+use std::process::Command;
+use std::io::{self, Write};
 
 use deltachat::config;
 use deltachat::configure::*;
@@ -516,25 +518,20 @@ unsafe fn handle_cmd(line: &str, ctx: Arc<RwLock<Context>>) -> Result<ExitResult
         }
         "getqr" | "getbadqr" => {
             start_threads(ctx.clone());
-            let qrstr =
-                dc_get_securejoin_qr(&ctx.read().unwrap(), arg1.parse().unwrap_or_default());
-            if !qrstr.is_null() && 0 != *qrstr.offset(0isize) as libc::c_int {
-                if arg0 == "getbadqr" && strlen(qrstr) > 40 {
-                    let mut i: libc::c_int = 12i32;
-                    while i < 22i32 {
-                        *qrstr.offset(i as isize) = '0' as i32 as libc::c_char;
-                        i += 1
+            if let Some(mut qr) = dc_get_securejoin_qr(&ctx.read().unwrap(), arg1.parse().unwrap_or_default()) {
+                if !qr.is_empty() {
+                    if arg0 == "getbadqr" && qr.len() > 40 {
+                        qr.replace_range(12..22, "0000000000")
                     }
+                    println!("{}", qr);
+                    let output = Command::new("qrencode")
+                            .args(&["-t", "ansiutf8", format!("\"{}\"", qr.as_str()).as_str(), "-o", "-"])
+                            .output()
+                            .expect("failed to execute process");
+                    io::stdout().write_all(&output.stdout).unwrap();
+                    io::stderr().write_all(&output.stderr).unwrap();
                 }
-                println!("{}", to_string(qrstr as *const _));
-                let syscmd = dc_mprintf(
-                    b"qrencode -t ansiutf8 \"%s\" -o -\x00" as *const u8 as *const libc::c_char,
-                    qrstr,
-                );
-                system(syscmd);
-                free(syscmd as *mut libc::c_void);
             }
-            free(qrstr as *mut libc::c_void);
         }
         "joinqr" => {
             start_threads(ctx.clone());

src/dc_securejoin.rs

@@ -25,12 +25,17 @@ use crate::x::*;
 pub unsafe fn dc_get_securejoin_qr(
     context: &Context,
     group_chat_id: uint32_t,
-) -> *mut libc::c_char {
+) -> Option<String> {
     /* =========================================================
     ====             Alice - the inviter side            ====
     ====   Step 1 in "Setup verified contact" protocol   ====
     ========================================================= */
 
+    let cleanup = |fingerprint, qr: Option<String>| {
+        free(fingerprint as *mut libc::c_void);
+        qr
+    };
+
     let mut fingerprint = ptr::null_mut();
     let mut qr: Option<String> = None;
 
@@ -53,19 +58,10 @@ pub unsafe fn dc_get_securejoin_qr(
     });
     let self_addr = context.sql.get_config(context, "configured_addr");
 
-    let cleanup = |fingerprint| {
-        free(fingerprint as *mut libc::c_void);
-
-        if let Some(qr) = qr {
-            qr.strdup()
-        } else {
-            std::ptr::null_mut()
-        }
-    };
 
     if self_addr.is_none() {
         error!(context, 0, "Not configured, cannot generate QR code.",);
-        return cleanup(fingerprint);
+        return cleanup(fingerprint, qr);
     }
 
     let self_addr = self_addr.unwrap();
@@ -77,7 +73,7 @@ pub unsafe fn dc_get_securejoin_qr(
     fingerprint = get_self_fingerprint(context);
 
     if fingerprint.is_null() {
-        return cleanup(fingerprint);
+        return cleanup(fingerprint, qr);
     }
 
     let self_addr_urlencoded = utf8_percent_encode(&self_addr, NON_ALPHANUMERIC).to_string();
@@ -103,7 +99,7 @@ pub unsafe fn dc_get_securejoin_qr(
                 context,
                 0, "Cannot get QR-code for chat-id {}", group_chat_id,
             );
-            return cleanup(fingerprint);
+            return cleanup(fingerprint, qr);
         }
     } else {
         Some(format!(
@@ -118,7 +114,7 @@ pub unsafe fn dc_get_securejoin_qr(
 
     info!(context, 0, "Generated QR code: {}", qr.as_ref().unwrap());
 
-    cleanup(fingerprint)
+    cleanup(fingerprint, qr)
 }
 
 fn get_self_fingerprint(context: &Context) -> *mut libc::c_char {