Re: [PATCH 02/13] declare overflow during base128 decoding when 1 MSB nonzero, not 7

"Dana How" <danahow@gmail.com> writes:

My understanding of the history is back when there was seek() but not lseek() nor SEEK_X macros, everybody passed bare integers and it was quite well established that 0 meant what SEEK_SET means now, so I would be quite surprised if there is _any_ platform that defines SEEK_SET to anything but zero.

Having said that, I wonder if this kind of thing can be caught with sparse. We should be able to express (or perhaps sparse could have a built-in rule that says) something like "although the standard says the third parameter to lseek() can be any integer, you should not use anything but SEEK_X preprocessor macros; also SEEK_X preprocessor macros, although they are typically just "#define"s of small integer literals, can never appear anywhere other than the third parameter as seek() and lseek()". I realize that there needs some data-flow analysis to allow a code like this, though:

	int move_to(int fd, ofs_t offset, int relative)
	{
		int whence = SEEK_SET;

	        if (relative) {
                	whence = SEEK_CUR;
	                offset += relative;
	        }
		return lseek(fd, offset, whence) != (off_t)-1;
	}

Very true, and that is why I said I am going to take the patch.