From mboxrd@z Thu Jan 1 00:00:00 1970 From: random832@fastmail.us (Random832) Date: Thu, 31 Jan 2013 18:52:22 -0500 Subject: [TUHS] History of strncpy In-Reply-To: References: <1301231756.AA27240@ivan.Harhan.ORG> <20130123214651.GF22559@mercury.ccil.org> <20130124060205.GQ24498@bitmover.com> <1AFADE66-7F72-4776-8738-EC27748DAF33@ronnatalie.com> Message-ID: <510B03B6.6010708@fastmail.us> On 1/24/2013 9:52 AM, Warner Losh wrote: > On Jan 24, 2013, at 7:42 AM, Ronald Natalie wrote: >> Amen. For practical matters, there is no way given the rest of the >> library that an implementation can do anything other than multiply >> the two middle args together. Is there any part of the rest of the library that will be broken if it does something like call (e.g. on UNIX) fflush (or _flsbuf), fileno, and write in a loop? vfprintf doesn't call fwrite, so it won't break sprintf. In theory all I can even think of is if some piece of userspace code made assumptions about the state of a setvbuf buffer. > Historically the only implementation I know that didn't just multiply the two args together was on VAX/VMS's VAXC. The underlying filesystem had a notion of a file of records, so you'd get very different result from n * size, 1 and n, size. You might get a different result in terms of the resulting underlying file, and maybe in terms of performance, but given the requirements the standard puts on fread (which I don't imagine it would do if a then-prominent implementation violated them), I have to wonder what would happen, if this is the case, if you attempted to call fread when the file pointer is positioned on a different sized record, or in the middle of a record. Because for all the concessions to non-unix-like file systems the standard _does_ make (binary files may be padded with extra zero bytes [because they may not be able to be an arbitrary size], text files may have a maximum line length and may not be able to contain some control characters, heck, _everything_ the standard says about text files is non-unix-like), it's IIRC rather strict about "fread has equivalent results to getc in a loop".