On Mon, 23 May 2022 at 16:35, Richard Henderson <richard.hender...@linaro.org> wrote: > On 5/23/22 05:13, Peter Maydell wrote: > > The gdb implementation of the isatty call returns 0 or 1 on > > success, and -1 on failure (though the only failure mode it has > > is "you messed up the protocol packet format"): > > https://sourceware.org/git/?p=binutils-gdb.git;a=blob;f=gdb/remote-fileio.c;h=fe191fb6069a53a3844656a81e77069afa781946;hb=HEAD#l1039 > > Technically, isatty = 0 is failure not success and should also set ENOTTY.
There are multiple different APIs here with similar names but not necessarily always the exact same behaviour in all cases: Arm semihosting SYS_ISTTY: https://github.com/ARM-software/abi-aa/blob/main/semihosting/semihosting.rst#sys-istty-0x09 returns 1 if the handle identifies an interactive device. 0 if the handle identifies a file. A value other than 1 or 0 if an error occurs (and implicitly sets errno, I assume) GDB File-I/O isatty: https://sourceware.org/gdb/onlinedocs/gdb/isatty.html#isatty Returns 1 if fd refers to the GDB console, 0 otherwise Documentation doesn't say how it reports errors. Actual implementation returns -1 and sets errno. (We should probably report some of these spec issues as gdb bugs...) isatty() POSIX function: returns 1 for a terminal 0 with errno ENOTTY for not-a-terminal 0 with some other errno for error cases It looks like our 'host' implementation of the semihosting SYS_ISTTY doesn't correctly do the matching up between the semihosting spec and the isatty() function, so it will return the wrong value for the error case. thanks -- PMM
