Prefer stpcpy to strcat

* admin/merge-gnulib (GNULIB_MODULES): Add stpcpy.
* lib/gnulib.mk, m4/gnulib-comp.m4: Regenerate.
* lib/stpcpy.c, m4/stpcpy.m4: New files, from gnulib.
* lib-src/ebrowse.c (sym_scope_1, operator_name, open_file):
* lib-src/emacsclient.c (get_server_config, set_local_socket)
(start_daemon_and_retry_set_socket):
* lib-src/etags.c (main, C_entries, relative_filename):
* lib-src/pop.c (sendline):
* lib-src/update-game-score.c (main):
* lwlib/xlwmenu.c (resource_widget_value):
* src/callproc.c (child_setup):
* src/dbusbind.c (xd_signature_cat):
* src/doc.c (get_doc_string, Fsnarf_documentation):
* src/editfns.c (Fuser_full_name):
* src/frame.c (xrdb_get_resource):
* src/gtkutil.c (xg_get_file_with_chooser):
* src/tparam.c (tparam1):
* src/xfns.c (xic_create_fontsetname):
* src/xrdb.c (gethomedir, get_user_db, get_environ_db):
* src/xsmfns.c (smc_save_yourself_CB):
Rewrite to avoid the need for strcat, typically by using stpcpy
and/or lispstpcpy.  strcat tends to be part of O(N**2) algorithms.
* src/doc.c (sibling_etc):
* src/xrdb.c (xdefaults):
Now a top-level static constant.

10 files changed, 71 insertions, 90 deletions

diff --git a/src/callproc.c b/src/callproc.c
index a677334b3b7..f40ed3244a5 100644
--- a/src/callproc.c
+++ b/src/callproc.c
@@ -1315,13 +1315,10 @@ child_setup (int in, int out, int err, char **new_argv, bool set_pgrp,
 
     if (STRINGP (display))
       {
-        char *vdata;
-
         if (MAX_ALLOCA - sizeof "DISPLAY=" < SBYTES (display))
           exec_failed (new_argv[0], ENOMEM);
-        vdata = alloca (sizeof "DISPLAY=" + SBYTES (display));
-        strcpy (vdata, "DISPLAY=");
-        strcat (vdata, SSDATA (display));
+        char *vdata = alloca (sizeof "DISPLAY=" + SBYTES (display));
+        lispstpcpy (stpcpy (vdata, "DISPLAY="), display);
         new_env = add_env (env, new_env, vdata);
       }
 
diff --git a/src/dbusbind.c b/src/dbusbind.c
index 4852739d8e4..983b05c4206 100644
--- a/src/dbusbind.c
+++ b/src/dbusbind.c
@@ -357,7 +357,7 @@ xd_signature_cat (char *signature, char const *x)
   ptrdiff_t xlen = strlen (x);
   if (DBUS_MAXIMUM_SIGNATURE_LENGTH - xlen <= siglen)
     string_overflow ();
-  strcat (signature, x);
+  strcpy (signature + siglen, x);
 }
 
 /* Compute SIGNATURE of OBJECT.  It must have a form that it can be
diff --git a/src/doc.c b/src/doc.c
index 1b87c23e949..1d9c330d12c 100644
--- a/src/doc.c
+++ b/src/doc.c
@@ -42,6 +42,8 @@ static ptrdiff_t get_doc_string_buffer_size;
 
 static unsigned char *read_bytecode_pointer;
 
+static char const sibling_etc[] = "../etc/";
+
 /* `readchar' in lread.c calls back here to fetch the next byte.
    If UNREADFLAG is 1, we unread a byte.  */
 
@@ -80,7 +82,6 @@ get_doc_string (Lisp_Object filepos, bool unibyte, bool definition)
 {
   char *from, *to, *name, *p, *p1;
   int fd;
-  ptrdiff_t minsize;
   int offset;
   EMACS_INT position;
   Lisp_Object file, tem, pos;
@@ -113,21 +114,14 @@ get_doc_string (Lisp_Object filepos, bool unibyte, bool definition)
 
   tem = Ffile_name_absolute_p (file);
   file = ENCODE_FILE (file);
-  if (NILP (tem))
-    {
-      Lisp_Object docdir = ENCODE_FILE (Vdoc_directory);
-      minsize = SCHARS (docdir);
-      /* sizeof ("../etc/") == 8 */
-      if (minsize < 8)
-        minsize = 8;
-      name = SAFE_ALLOCA (minsize + SCHARS (file) + 8);
-      char *z = lispstpcpy (name, docdir);
-      strcpy (z, SSDATA (file));
-    }
-  else
-    {
-      name = SSDATA (file);
-    }
+  Lisp_Object docdir
+    = NILP (tem) ? ENCODE_FILE (Vdoc_directory) : empty_unibyte_string;
+  ptrdiff_t docdir_sizemax = SBYTES (docdir) + 1;
+#ifndef CANNOT_DUMP
+  docdir_sizemax = max (docdir_sizemax, sizeof sibling_etc);
+#endif
+  name = SAFE_ALLOCA (docdir_sizemax + SBYTES (file));
+  lispstpcpy (lispstpcpy (name, docdir), file);
 
   fd = emacs_open (name, O_RDONLY, 0);
   if (fd < 0)
@@ -137,8 +131,7 @@ get_doc_string (Lisp_Object filepos, bool unibyte, bool definition)
         {
           /* Preparing to dump; DOC file is probably not installed.
              So check in ../etc.  */
-          strcpy (name, "../etc/");
-          strcat (name, SSDATA (file));
+          lispstpcpy (stpcpy (name, sibling_etc), file);
 
           fd = emacs_open (name, O_RDONLY, 0);
         }
@@ -580,7 +573,6 @@ the same file name is found in the `doc-directory'.  */)
       (0)
 #endif /* CANNOT_DUMP */
     {
-      static char const sibling_etc[] = "../etc/";
       dirname = sibling_etc;
       dirlen = sizeof sibling_etc - 1;
     }
@@ -594,8 +586,7 @@ the same file name is found in the `doc-directory'.  */)
   count = SPECPDL_INDEX ();
   USE_SAFE_ALLOCA;
   name = SAFE_ALLOCA (dirlen + SBYTES (filename) + 1);
-  strcpy (name, dirname);
-  strcat (name, SSDATA (filename));     /*** Add this line ***/
+  lispstpcpy (stpcpy (name, dirname), filename);        /*** Add this line ***/
 
   /* Vbuild_files is nil when temacs is run, and non-nil after that.  */
   if (NILP (Vbuild_files))
diff --git a/src/editfns.c b/src/editfns.c
index 0a07886934c..430c4c91fb3 100644
--- a/src/editfns.c
+++ b/src/editfns.c
@@ -1350,10 +1350,9 @@ name, or nil if there is no such user.  */)
       USE_SAFE_ALLOCA;
       char *r = SAFE_ALLOCA (strlen (p) + SBYTES (login) + 1);
       memcpy (r, p, q - p);
-      r[q - p] = 0;
-      strcat (r, SSDATA (login));
+      char *s = lispstpcpy (&r[q - p], login);
       r[q - p] = upcase ((unsigned char) r[q - p]);
-      strcat (r, q + 1);
+      strcpy (s, q + 1);
       full = build_string (r);
       SAFE_FREE ();
     }
diff --git a/src/frame.c b/src/frame.c
index 31273665e88..2ad1c1b52b7 100644
--- a/src/frame.c
+++ b/src/frame.c
@@ -4076,23 +4076,23 @@ xrdb_get_resource (XrmDatabase rdb, Lisp_Object attribute, Lisp_Object class, Li
 
   /* Start with emacs.FRAMENAME for the name (the specific one)
      and with `Emacs' for the class key (the general one).  */
-  lispstpcpy (name_key, Vx_resource_name);
-  lispstpcpy (class_key, Vx_resource_class);
+  char *nz = lispstpcpy (name_key, Vx_resource_name);
+  char *cz = lispstpcpy (class_key, Vx_resource_class);
 
-  strcat (class_key, ".");
-  strcat (class_key, SSDATA (class));
+  *cz++ = '.';
+  cz = lispstpcpy (cz, class);
 
   if (!NILP (component))
     {
-      strcat (class_key, ".");
-      strcat (class_key, SSDATA (subclass));
+      *cz++ = '.';
+      lispstpcpy (cz, subclass);
 
-      strcat (name_key, ".");
-      strcat (name_key, SSDATA (component));
+      *nz++ = '.';
+      nz = lispstpcpy (nz, component);
     }
 
-  strcat (name_key, ".");
-  strcat (name_key, SSDATA (attribute));
+  *nz++ = '.';
+  lispstpcpy (nz, attribute);
 
   char *value = x_get_string_resource (rdb, name_key, class_key);
   SAFE_FREE();
diff --git a/src/gtkutil.c b/src/gtkutil.c
index 9465d5479df..f61cbc2c85c 100644
--- a/src/gtkutil.c
+++ b/src/gtkutil.c
@@ -1839,12 +1839,12 @@ xg_get_file_with_chooser (struct frame *f,
 
   if (x_gtk_file_dialog_help_text)
     {
-      msgbuf[0] = '\0';
+      char *z = msgbuf;
       /* Gtk+ 2.10 has the file name text entry box integrated in the dialog.
          Show the C-l help text only for versions < 2.10.  */
       if (gtk_check_version (2, 10, 0) && action != GTK_FILE_CHOOSER_ACTION_SAVE)
-        strcat (msgbuf, "\nType C-l to display a file name text entry box.\n");
-      strcat (msgbuf, "\nIf you don't like this file selector, use the "
+        z = stpcpy (z, "\nType C-l to display a file name text entry box.\n");
+      strcpy (z, "\nIf you don't like this file selector, use the "
               "corresponding\nkey binding or customize "
               "use-file-dialog to turn it off.");
 
diff --git a/src/tparam.c b/src/tparam.c
index e02cea3689e..b0cd0047ba2 100644
--- a/src/tparam.c
+++ b/src/tparam.c
@@ -255,9 +255,9 @@ tparam1 (const char *string, char *outstring, int len,
     }
   *op = 0;
   while (doup-- > 0)
-    strcat (op, up);
+    op = stpcpy (op, up);
   while (doleft-- > 0)
-    strcat (op, left);
+    op = stpcpy (op, left);
   return outstring;
 }
 
diff --git a/src/xfns.c b/src/xfns.c
index 1b17311f99c..ba2601daca4 100644
--- a/src/xfns.c
+++ b/src/xfns.c
@@ -1710,13 +1710,14 @@ xic_create_fontsetname (const char *base_fontname, int motif)
 {
   const char *sep = motif ? ";" : ",";
   char *fontsetname;
+  char *z;
 
   /* Make a fontset name from the base font name.  */
   if (xic_default_fontset == base_fontname)
     {
       /* There is no base font name, use the default.  */
       fontsetname = xmalloc (strlen (base_fontname) + 2);
-      strcpy (fontsetname, base_fontname);
+      z = stpcpy (fontsetname, base_fontname);
     }
   else
     {
@@ -1737,9 +1738,9 @@ xic_create_fontsetname (const char *base_fontname, int motif)
              Use the specified font plus the default.  */
           fontsetname = xmalloc (strlen (base_fontname)
                                  + strlen (xic_default_fontset) + 3);
-          strcpy (fontsetname, base_fontname);
-          strcat (fontsetname, sep);
-          strcat (fontsetname, xic_default_fontset);
+          z = stpcpy (fontsetname, base_fontname);
+          z = stpcpy (z, sep);
+          z = stpcpy (z, xic_default_fontset);
         }
       else
         {
@@ -1800,27 +1801,26 @@ xic_create_fontsetname (const char *base_fontname, int motif)
           /* Build the font spec that matches all.  */
           len = p - p2 + strlen (allcs) + strlen (all) + strlen (allfamilies) + 1;
           font_all = alloca (len);
-          strcpy (font_all, allfamilies);
-          strcat (font_all, all);
-          memcpy (font_all + strlen (all) + strlen (allfamilies), p2, p - p2);
-          strcpy (font_all + strlen (all) + strlen (allfamilies) + (p - p2),
-                  allcs);
+          z = stpcpy (font_all, allfamilies);
+          z = stpcpy (z, all);
+          memcpy (z, p2, p - p2);
+          strcpy (z + (p - p2), allcs);
 
           /* Build the actual font set name.  */
           len = strlen (base_fontname) + strlen (font_allcs)
             + strlen (font_allfamilies) + strlen (font_all) + 5;
           fontsetname = xmalloc (len);
-          strcpy (fontsetname, base_fontname);
-          strcat (fontsetname, sep);
-          strcat (fontsetname, font_allcs);
-          strcat (fontsetname, sep);
-          strcat (fontsetname, font_allfamilies);
-          strcat (fontsetname, sep);
-          strcat (fontsetname, font_all);
+          z = stpcpy (fontsetname, base_fontname);
+          z = stpcpy (z, sep);
+          z = stpcpy (z, font_allcs);
+          z = stpcpy (z, sep);
+          z = stpcpy (z, font_allfamilies);
+          z = stpcpy (z, sep);
+          z = stpcpy (z, font_all);
         }
     }
   if (motif)
-    return strcat (fontsetname, ":");
+    strcpy (z, ":");
   return fontsetname;
 }
 #endif /* HAVE_X_WINDOWS && USE_X_TOOLKIT */
diff --git a/src/xrdb.c b/src/xrdb.c
index 32ad3c7f01e..e21206d0800 100644
--- a/src/xrdb.c
+++ b/src/xrdb.c
@@ -232,9 +232,10 @@ gethomedir (void)
   if (ptr == NULL)
     return xstrdup ("/");
 
-  copy = xmalloc (strlen (ptr) + 2);
-  strcpy (copy, ptr);
-  return strcat (copy, "/");
+  ptrdiff_t len = strlen (ptr);
+  copy = xmalloc (len + 2);
+  strcpy (copy + len, "/");
+  return memcpy (copy, ptr, len);
 }
 
 
@@ -334,6 +335,7 @@ get_user_app (const char *class)
   return db;
 }
 
+static char const xdefaults[] = ".Xdefaults";
 
 static XrmDatabase
 get_user_db (Display *display)
@@ -351,16 +353,12 @@ get_user_db (Display *display)
     db = XrmGetStringDatabase (xdefs);
   else
     {
-      char *home;
-      char *xdefault;
-
-      home = gethomedir ();
-      xdefault = xmalloc (strlen (home) + sizeof ".Xdefaults");
-      strcpy (xdefault, home);
-      strcat (xdefault, ".Xdefaults");
-      db = XrmGetFileDatabase (xdefault);
-      xfree (home);
-      xfree (xdefault);
+      char *home = gethomedir ();
+      ptrdiff_t homelen = strlen (home);
+      char *filename = xrealloc (home, homelen + sizeof xdefaults);
+      strcpy (filename + homelen, xdefaults);
+      db = XrmGetFileDatabase (filename);
+      xfree (filename);
     }
 
 #ifdef HAVE_XSCREENRESOURCESTRING
@@ -380,24 +378,22 @@ static XrmDatabase
 get_environ_db (void)
 {
   XrmDatabase db;
-  char *p;
-  char *path = 0;
+  char *p = getenv ("XENVIRONMENT");
+  char *filename = 0;
 
-  if ((p = getenv ("XENVIRONMENT")) == NULL)
+  if (!p)
     {
-      static char const xdefaults[] = ".Xdefaults-";
       char *home = gethomedir ();
-      char const *host = SSDATA (Vsystem_name);
-      ptrdiff_t pathsize = (strlen (home) + sizeof xdefaults
-                            + SBYTES (Vsystem_name));
-      path = xrealloc (home, pathsize);
-      strcat (strcat (path, xdefaults), host);
-      p = path;
+      ptrdiff_t homelen = strlen (home);
+      ptrdiff_t filenamesize = (homelen + sizeof xdefaults
+                                + SBYTES (Vsystem_name));
+      p = filename = xrealloc (home, filenamesize);
+      lispstpcpy (stpcpy (filename + homelen, xdefaults), Vsystem_name);
     }
 
   db = XrmGetFileDatabase (p);
 
-  xfree (path);
+  xfree (filename);
 
   return db;
 }
diff --git a/src/xsmfns.c b/src/xsmfns.c
index cd4f9ce57fa..8a835cf95f1 100644
--- a/src/xsmfns.c
+++ b/src/xsmfns.c
@@ -230,8 +230,7 @@ smc_save_yourself_CB (SmcConn smcConn,
   props[props_idx]->vals[vp_idx++].value = emacs_program;
 
   smid_opt = xmalloc (strlen (SMID_OPT) + strlen (client_id) + 1);
-  strcpy (smid_opt, SMID_OPT);
-  strcat (smid_opt, client_id);
+  strcpy (stpcpy (smid_opt, SMID_OPT), client_id);
 
   props[props_idx]->vals[vp_idx].length = strlen (smid_opt);
   props[props_idx]->vals[vp_idx++].value = smid_opt;
@@ -242,8 +241,7 @@ smc_save_yourself_CB (SmcConn smcConn,
   if (cwd)
     {
       chdir_opt = xmalloc (strlen (CHDIR_OPT) + strlen (cwd) + 1);
-      strcpy (chdir_opt, CHDIR_OPT);
-      strcat (chdir_opt, cwd);
+      strcpy (stpcpy (chdir_opt, CHDIR_OPT), cwd);
 
       props[props_idx]->vals[vp_idx].length = strlen (chdir_opt);
       props[props_idx]->vals[vp_idx++].value = chdir_opt;