On Wed, Mar 28, 2012 at 03:42:21PM -0500, Jonathan Nieder wrote:
> > + path = mkpath("%.*s/%s", (int)(end - p), p, file);
> [...]
> - (end - p) is not guaranteed to fit inside an int. What should happen
> when my PATH is very long?
That is the cost of using the mkpath convenience function (otherwise,
the compiler will complain that ".*" expects an int). We can do it
manually, but in practice, do you really expect your PATH environment
variable to overflow an int?
> - the existence check would be simpler spelled as access(path, F_OK).
Yeah, I think that is nicer. I went with !stat() because that is our
usual file_exists test, and I was wondering if there were any
portability issues with access(..., F_OK). However, we seem to use it
already in other places, so it should be fine.
> - the above checks if there is _any_ nonexecutable instance of "file"
> in the directories listed in $PATH, but isn't what we want to check
> whether _all_ of them are nonexecutable?
If there is one that is executable, then execvp would not have returned.
So if there is any entry that is non-executable, then they all are. And
we don't care about the actual number; we only care whether there is one
(in which case it is no ENOENT).
> > +int sane_execvp(const char *file, char * const argv[])
> > +{
> > + int ret = execvp(file, argv);
> > + if (ret < 0 && errno == EACCES && !file_in_path_is_nonexecutable(file))
> > + errno = ENOENT;
> > + return ret;
> > +}
>
> Makes sense. No objections from me.
>
> if (!execvp(file, argv))
> return 0;
> [...]
> return -1;
That is nicer; I have a general avoidance of rewriting return codes, but I
think it is safe to translate a non-zero execvp result into -1.
> /*
> * When a command can't be found because one of the directories
> * listed in $PATH is unsearchable, execvp reports EACCES, but
> * careful usability testing (read: analysis of occasional bug
> * reports) reveals that "No such file or directory" is more
> * intuitive.
> */
> if (errno == EACCES && cannot_find_in_PATH(file))
> errno = ENOENT;
I think we can even simplify cannot_find to "!exists_in_PATH" to make
it even simpler. If it exists and execvp did not execute it, then it
must be non-executable (or there is a race condition :) ).
-Peff
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