Re: [HACKERS] Does this make sense:

>
> >
> > char *
> > crypt_getpwdfilename()
> > {
> >
> > static char *pfnam = NULL;
> >
> > if (!pfnam)
> > {
> > int bufsize;
> > bufsize = strlen(DataDir) + strlen(CRYPT_PWD_FILE) + 2;
> > pfnam = (char *) palloc(bufsize);
> > spprintf(pfnam, bufsize, "%s/%s", DataDir, CRYPT_PWD_FILE);
> > }
> >
> > return pfnam;
> > }
> >
> > Why the check for '!ipfnam'? Seems useless since we are setting it to
> > NULL the line before...no?
>
> Actually, no. We are declaring it as static, so the first time the
> function is called, it is set to NULL. After that, it is not
> initialized for each function call because a static local variable's
> value is kept between function calls. It is like a global variable in
> its duration, but in local scope.
>
> This is an old trick to run the initialization code only the first time
> the function is called.

But is it good then to use palloc() instead of malloc()?
Anything palloc()'d is thrown away when the memory context in
which it is made get's destroyed. So you have to care about
the memory context in which the call is made. If under some
(but not all) circumstances the FIRST call is made in the
wrong mcxt, the pointer maybe get's corrupted later.

Jan

--

#======================================================================#
# It's easier to get forgiveness for being wrong than for being right. #
# Let's break this rule - forgive me. #
#======================================== jwieck(at)debis(dot)com (Jan Wieck) #