diff --git a/dpid/dpid.cc b/dpid/dpid.cc
index 7503bb0..b969081 100644
--- a/dpid/dpid.cc
+++ b/dpid/dpid.cc
@@ -39,6 +39,8 @@
 
 #include "../dpip/dpip.h"
 
+using namespace std::literals::string_literals;
+
 #define DPI_EXT (".dpi" EXEEXT)
 
 #define QUEUE 5
@@ -52,10 +54,8 @@ char *SharedKey = NULL;
  */
 void cleanup(void)
 {
-   char *fname;
-   fname = dStrconcat(dGethomedir(), "/", dotDILLO_DPID_COMM_KEYS, NULL);
-   unlink(fname);
-   dFree(fname);
+   std::string fname = dGethomedir() + "/"s + dotDILLO_DPID_COMM_KEYS;
+   unlink(fname.c_str());
 }
 
 /*! Free memory used to describe
diff --git a/src/html.cc b/src/html.cc
index ec17d0f..18e755b 100644
--- a/src/html.cc
+++ b/src/html.cc
@@ -558,11 +558,6 @@ void DilloHtml::write(char *Buf, int BufSize, int Eof)
    int bufsize = BufSize - Start_Ofs;
 
    _MSG("DilloHtml::write BufSize=%d Start_Ofs=%d\n", BufSize, Start_Ofs);
-#if 0
-   char *aux = dStrndup(Buf, BufSize);
-   MSG(" {%s}\n", aux);
-   dFree(aux);
-#endif
 
    /* Update Start_Buf. It may be used after the parser is stopped */
    Start_Buf = Buf;
diff --git a/src/ui.cc b/src/ui.cc
index b8fc2e6..da6e3c7 100644
--- a/src/ui.cc
+++ b/src/ui.cc
@@ -36,6 +36,8 @@
 #include "history.hh"
 #include "nav.hh"
 
+using namespace std::literals::string_literals;
+
 struct iconset {
    Fl_Image *ImgMeterOK, *ImgMeterBug,
             *ImgHome, *ImgReload, *ImgSave, *ImgBook, *ImgTools,
@@ -239,19 +241,17 @@ static void search_cb(Fl_Widget *wid, void *data)
  */
 static void help_cb(Fl_Widget *w, void *)
 {
-   char *path = dStrconcat(DILLO_DOCDIR, "user_help.html", NULL);
+   std::string path = DILLO_DOCDIR + "user_help.html"s;
    BrowserWindow *bw = a_UIcmd_get_bw_by_widget(w);
 
-   if (access(path, R_OK) == 0) {
-      char *urlstr = dStrconcat("file:", path, NULL);
-      a_UIcmd_open_urlstr(bw, urlstr);
-      dFree(urlstr);
+   if (access(path.c_str(), R_OK) == 0) {
+      std::string urlstr = "file:" + path;
+      a_UIcmd_open_urlstr(bw, urlstr.c_str());
    } else {
       MSG("Can't read local help file at \"%s\"."
-          " Getting remote help...\n", path);
+          " Getting remote help...\n", path.c_str());
       a_UIcmd_open_urlstr(bw, "https://dillo-browser.github.io/user_help.html");
    }
-   dFree(path);
 }
 
 /**
diff --git a/src/uicmd.cc b/src/uicmd.cc
index a5d0dfe..5d36077 100644
--- a/src/uicmd.cc
+++ b/src/uicmd.cc
@@ -52,6 +52,8 @@
 
 #include "nav.hh"
 
+#include <algorithm>
+
 //#define DEFAULT_TAB_LABEL "-.untitled.-"
 #define DEFAULT_TAB_LABEL "-.new.-"
 
@@ -63,6 +65,8 @@ using namespace dw::core;
 // FLTK related
 using namespace dw::fltk;
 
+using namespace std::literals::string_literals;
+
 
 /*
  * Local data
@@ -105,13 +109,13 @@ public:
    void ui(UI *pui) { ui_ = pui; }
    UI *ui(void) { return ui_; }
    void focus_num(uint_t fn) { focus_num_ = fn; }
-   uint_t focus_num(void) { return focus_num_; }
+   uint_t focus_num() const { return focus_num_; }
 };
 
-static int btn_cmp(const void *p1, const void *p2)
+static int
+btn_cmp( const CustTabButton *const p1, const CustTabButton *const p2 )
 {
-   return ((*(CustTabButton * const *)p1)->focus_num() -
-           (*(CustTabButton * const *)p2)->focus_num() );
+   return p1->focus_num() - p2->focus_num();
 }
 
 /**
@@ -135,14 +139,13 @@ class CustTabs : public Fl_Group {
          ++focus_counter;
       else {
          /* wrap & normalize old numbers here */
-         CustTabButton **btns = dNew(CustTabButton*, num_tabs());
+         std::vector< CustTabButton * > btns;
          for (int i = 0; i < num_tabs(); ++i)
-            btns[i] = (CustTabButton*)Pack->child(i);
-         qsort(btns, num_tabs(), sizeof(CustTabButton *), btn_cmp);
+            btns.push_back( (CustTabButton*)Pack->child( i ) ) ;
+         std::ranges::sort( btns, btn_cmp );
          focus_counter = 0;
-         for (int i = 0; i < num_tabs(); ++i)
-            btns[i]->focus_num(focus_counter++);
-         dFree(btns);
+         for( auto *btn: btns )
+            btn->focus_num(focus_counter++);
       }
    }
 
@@ -760,7 +763,7 @@ void a_UIcmd::a_UIcmd_open_urlstr(BrowserWindow *bw, const char *urlstr)
 {
    char *new_urlstr;
    char *search_urlstr = NULL;
-   DilloUrl *url;
+   std::unique_ptr< DilloUrl > url;
    int ch;
 
    if ((search_urlstr = UIcmd_find_search_str(urlstr))) {
@@ -774,20 +777,19 @@ void a_UIcmd::a_UIcmd_open_urlstr(BrowserWindow *bw, const char *urlstr)
          /* file URI */
          ch = new_urlstr[5];
          if (!ch || ch == '.') {
-            url = a_Url_new(Paths::getOldWorkingDir(), "file:").release();
+            url = a_Url_new(Paths::getOldWorkingDir(), "file:");
          } else {
-            url = a_Url_new(new_urlstr, "file:").release();
+            url = a_Url_new(new_urlstr, "file:");
          }
 
       } else {
          /* common case */
-         url = a_Url_new(new_urlstr, NULL).release();
+         url = a_Url_new(new_urlstr, NULL);
       }
       dFree(new_urlstr);
 
       if (url) {
-         a_UIcmd_open_url(bw, url);
-         delete url;
+         a_UIcmd_open_url(bw, url.release());
       }
    }
    dFree(search_urlstr);
@@ -1215,9 +1217,8 @@ const char *a_UIcmd::a_UIcmd_get_passwd(const char *user)
 {
    const char *passwd;
    const char *title = "Flenser: Password";
-   char *msg = dStrconcat("Password for user \"", user, "\"", NULL);
-   passwd = a_Dialog_passwd(title, msg);
-   dFree(msg);
+   std::string msg= "Password for user \""s + user + "\"";
+   passwd = a_Dialog_passwd(title, msg.c_str());
    return passwd;
 }