Hi Junio,
On Wed, 26 Dec 2018, Junio C Hamano wrote:
> Paul-Sebastian Ungureanu <ungureanupaulsebastian@xxxxxxxxx> writes:
>
> > +static void set_env_if(const char *key, const char *value, int *given, int bit)
> > +{
> > + if ((*given & bit) || getenv(key))
> > + return; /* nothing to do */
> > + setenv(key, value, 0);
> > + *given |= bit;
> > +}
>
> We call setenv(3) with overwrite=0 but we protect the call with a
> check for existing value with getenv(3), which feels a bit like an
> anti-pattern. Wouldn't the following be simpler to follow, I wonder?
>
> if (!(*given & bit)) {
> setenv(key, value, 1);
> *given |= bit;
> }
>
> The only case these two may behave differently is when '*given' does
> not have the 'bit' set but the environment 'key' already exists.
Indeed, this is the case where your version would actually do the wrong
thing. Imagine that GIT_AUTHOR_NAME is set already. Your code would
*override* it. But that is not what we want to do here. We want to *fall
back* if there is no already-configured value.
And of course we won't set the `given` bit if we don't fall back here;
that should be done somewhere else, where that environment variable (that
we *refuse* to overwrite) is *actually* used.
Ciao,
Dscho
> The proposed patch will leave 'bit' in '*given' unset, so when a
> later code says "let's see if author_ident is explicitly given, and
> complain otherwise", such a check will trigger and cause complaint.
>
> On the other hand, the simplified version does not allow the
> "explicitly-given" bits to be left unset, so it won't cause
> complaint.
>
> Isn't it a BUG() if *given lacks 'bit' when the corresponding
> environment variable 'key' is missing? IOW, I would understand
> an implementation that is more elaborate than the simplified one I
> just gave above were something like
>
> if (!(*given & bit)) {
> if (getenv(key))
> BUG("why does %s exist and no %x bit set???", key, bit);
> setenv(key, value, 0);
> *given |= bit;
> }
>
> but I do not quite understand the reasoning behind the "check either
> the bit, or the environment variable" in the proposed patch.
>
> > +void prepare_fallback_ident(const char *name, const char *email)
> > +{
> > + set_env_if("GIT_AUTHOR_NAME", name,
> > + &author_ident_explicitly_given, IDENT_NAME_GIVEN);
> > + set_env_if("GIT_AUTHOR_EMAIL", email,
> > + &author_ident_explicitly_given, IDENT_MAIL_GIVEN);
> > + set_env_if("GIT_COMMITTER_NAME", name,
> > + &committer_ident_explicitly_given, IDENT_NAME_GIVEN);
> > + set_env_if("GIT_COMMITTER_EMAIL", email,
> > + &committer_ident_explicitly_given, IDENT_MAIL_GIVEN);
> > +}
>
> Introducing this function alone without a caller and without
> function doc is a bit unfriendly to future callers, who must be
> careful when to call it, I think. For example, they must know that
> it will be a disaster if they call this before they call
> git_ident_config(), right?
>
> > +
> > static int buf_cmp(const char *a_begin, const char *a_end,
> > const char *b_begin, const char *b_end)
> > {
>
>
>
