MT#59962 ModSys: refactor SCTmpNamAction using `mkstemp()`

Instead of using the `tmpnam()` which doesn't exclude
race conditions on the system (same filenames created
simultaneously), because it doesn't open/reserve the file,
just use the `mkstemp()` which actually genereates a filename
and creates the file for the process.

Upon creating the file, close the FD, as not needed atm.
This file can be then later opened using `SCPopenAction`
or anything alike.

Current new implementation does not unlink the file from
the filesystem and a user of it has to explicitly do that
later with for example the `sys.unlink()` from this same
library.

Additionally: to be able to have excplicit file path (so dir),
add a second parameter to this function to provide a directory.

Fixes:
    warning: the use of `tmpnam' is dangerous, better use `mkstemp'

Change-Id: Ib5e89461b2d2288be77d5f1a899e5293b76ebf90

apps/dsm/mods/mod_sys/ModSys.cpp

@@ -247,14 +247,33 @@ EXEC_ACTION_START(SCUnlinkArrayAction) {
   }
 } EXEC_ACTION_END;
 
+/**
+ * Must only be used with awareness that dst directory exists,
+ * e.g. with `sys.mkdir` from this lib.
+ * Later, removal not handled automatically, so must be unlinked
+ * with something like `sys.unlink` from this lib.
+ */
+CONST_ACTION_2P(SCTmpNamAction, ',', true);
 EXEC_ACTION_START(SCTmpNamAction) {
-  string varname = resolveVars(arg, sess, sc_sess, event_params);
-  char fname[L_tmpnam];
-  if (!tmpnam(fname)) {
+
+  string varname = resolveVars(par1, sess, sc_sess, event_params);
+  string directory = resolveVars(par2, sess, sc_sess, event_params);
+
+  /* XXXXXX is required for mkstemp, this will be swapped with some random chars */
+  string path_template = directory + "/" + varname + "XXXXXX";
+
+  /* TODO: C-like strings here, possibly to rework later using C++ strings only? */
+  char tmpl[path_template.size() + 1];
+  strcpy(tmpl, path_template.c_str());
+
+  int fd = mkstemp(tmpl);
+
+  if (fd == -1) {
     ERROR("unique name cannot be generated\n");
     sc_sess->SET_ERRNO(DSM_ERRNO_FILE);
   } else {
-    sc_sess->var[varname] = fname;
+    close(fd); /* not needed atm */
+    sc_sess->var[varname] = tmpl;
     sc_sess->SET_ERRNO(DSM_ERRNO_OK);
   }
 } EXEC_ACTION_END;

apps/dsm/mods/mod_sys/ModSys.h

@@ -38,7 +38,7 @@ DEF_ACTION_1P(SCMkDirRecursiveAction);
 DEF_ACTION_2P(SCRenameAction);
 DEF_ACTION_1P(SCUnlinkAction);
 DEF_ACTION_2P(SCUnlinkArrayAction);
-DEF_ACTION_1P(SCTmpNamAction);
+DEF_ACTION_2P(SCTmpNamAction);
 DEF_ACTION_2P(SCPopenAction);
 
 DEF_ACTION_1P(SCSysGetTimestampAction);