Re: BUG #6166: configure from source fails with 'This platform is not thread-safe.' but was actually /tmp perms

Tom Lane wrote:
> Bruce Momjian <bruce(at)momjian(dot)us> writes:
> > Tom Lane wrote:
> >> (The error message seems to be suffering from a bad case of copy-and-
> >> paste-itis, too.)
>
> > Actually, it is accurate. The code is:
>
> > #ifdef WIN32
> > h1 = CreateFile(TEMP_FILENAME_1, GENERIC_WRITE, 0, NULL, OPEN_ALWAYS, 0, NULL);
> > h2 = CreateFile(TEMP_FILENAME_1, GENERIC_WRITE, 0, NULL, CREATE_NEW, 0, NULL);
> > if (h1 == INVALID_HANDLE_VALUE || GetLastError() != ERROR_FILE_EXISTS)
> > #else
> > if (open(TEMP_FILENAME_1, O_RDWR | O_CREAT, 0600) < 0 ||
> > open(TEMP_FILENAME_1, O_RDWR | O_CREAT | O_EXCL, 0600) >= 0)
> > #endif
> > {
> > fprintf(stderr, "Could not create file in current directory or\n");
> > fprintf(stderr, "could not generate failure for create file in current directory **\nexiting\n");
> > exit(1);
> > }
>
> > This code generates an errno == EEXIST in one thread, while another
> > thread generates errno == ENOENT, and this is how we test for errno
> > being thread-safe. If you have a cleaner way to do this, please let me
> > know. mkdir()?
>
> The problem with that is you're trying to make one error message serve
> for two extremely different failure conditions. I think this should be
> coded more like
>
> if (open(TEMP_FILENAME_1, O_RDWR | O_CREAT, 0600) < 0)
> {
> report suitable failure message;
> exit(1);
> }
> if (open(TEMP_FILENAME_1, O_RDWR | O_CREAT | O_EXCL, 0600) >= 0)
> {
> report suitable failure message;
> exit(1);
> }
>
> You would probably find that the messages could be a lot more clear and
> specific if they were done like that. Also, a file-related error
> message that doesn't provide the filename nor strerror(errno) is pretty
> much wrong on its face, in my book.

OK, I split apart the two operations with the attached, applied patch.
There must be an easier way to generate two unique errno values in a
platform-indepentent way, but I can't find it. I did simplify the
second ENOENT generation by just doing unlink twice.

I can't just set errno to a different value, can I?

I am not able to use strerror because I don't know if that is
thread-safe yet. I do have a C comment about it:

/*
* strerror() might not be thread-safe, and we already spawned thread
* 1 that uses it, so avoid using it.
*/

--
Bruce Momjian <bruce(at)momjian(dot)us> http://momjian.us
EnterpriseDB http://enterprisedb.com

+ It's impossible for everything to be true. +