because struct stat is no longer assumed to correspond to the structure used by the stat-family syscalls, it's not valid to make any of these syscalls directly using a buffer of type struct stat. commit 9493892021eac4edf1776d945bcdd3f7a96f6978 moved all logic around this change for stat-family functions into fstatat.c, making the others wrappers for it. but a few other direct uses of the syscall were overlooked. the ones in tmpnam/tempnam are harmless since the syscalls are just used to test for file existence. however, the uses in fchmodat and __map_file depend on getting accurate file properties, and these functions may actually have been broken one or more mips variants due to removal of conversion hacks from syscall_arch.h. as a low-risk fix, simply use struct kstat in place of struct stat in the affected places.
aside from the special value EOF, ungetc is specified to accept and convert values outside the range of unsigned char. conversion takes place automatically as part of assignment when storing into the buffer, but the return value is also required to be the resulting converted value, and this requirement was not satisfied. simplified from patch by Wang Jianjian.
commit cc3a4466605fe8dfc31f3b75779110ac93055bc1 fixed this for printf but neglected to fix wprintf. Previously, %lf caused a failure to output.
this probably saves a few bytes, avoids duplicating the clunky lseek/_llseek syscall convention in two places, and sets the stage for fixing broken seeks on x32 and mipsn32.
previously, POSIX erroneously required this to fail with EINVAL despite the traditional glibc implementation, on which the POSIX interface was based, allowing it. the resolution of Austin Group issue 818 removes the requirement to fail.
this is a requirement in POSIX that's omitted, and seemed potentially non-conforming, in the C standard. as such it was omitted here. however, as part of Austin Group issue #1170, the discrepancy was raised with WG14 and determined to be unintended; future versions of the C standard will require the error indicator to be set, as POSIX does.
POSIX requires setvbuf to return non-zero if `mode` is not one of _IONBF, _IOLBF, or _IOFBF.
the way gets was implemented in terms of fgets, it used the location of the null termination to determine where to find and remove the newline, if any. an embedded null byte prevented this from working. this also fixes a one-byte buffer overflow, whereby when gets read an N-byte line (not counting newline), it would store two null terminators for a total of N+2 bytes. it's unlikely that anyone would care that a function whose use is pretty much inherently a buffer overflow writes too much, but it could break the only possible correct uses of this function, in conjunction with input of known format from a trusted/same-privilege-domain source, where the buffer length may have been selected to exactly match a line length contract. there seems to be no correct way to implement gets in terms of a single call to fgets or scanf, and using multiple calls would require explicit locking, so we might as well just write the logic out explicitly character-at-a-time. this isn't fast, but nobody cares if a catastrophically unsafe function that's so bad it was removed from the C language is fast.
commit ddc947eda311331959c73dbc4491afcfe2326346 fixed the corresponding bug for exit which was introduced when commit 0b80a7b0404b6e49b0b724e3e3fe0ed5af3b08ef added support for caller-provided buffers, making it possible for stderr to be a buffered stream.