The read builtin could return an exit status of (128|SIGALRM) in two
circumstances:
1. If a signal is caught during the read syscall, then either the read
system call returns -1 with EINTR and the error is reported. (Otherwise it
must return a positive byte count, causing the built-in continues until it
gets a delimiter.)
2. If a signal is caught between read syscalls, it could (by a variety of
mechanisms) replace the exit status of the read built-in with a non zero
number. Presumably this is what you're seeing in fuzzing?
I will take a look at builtins/read.def when I get home. I suspect it's
looking at the "have I received SIGALRM" flag before looking at the "have I
read a delimiter" flag; I will report back on what I find.
On Fri, 4 Oct 2024, 22:18 Thomas Oettli via Bug reports for the GNU Bourne
Again SHell, <bug-bash@gnu.org> wrote:
> Configuration Information [Automatically generated, do not change]:
> Machine: x86_64
> OS: linux-gnu
> Compiler: x86_64-pc-linux-gnu-gcc
> Compilation CFLAGS: -O2 -pipe
> uname output: Linux testserver 6.6.47-gentoo #1 SMP Tue Aug 20 09:38:16
> CEST 2024 x86_64 Intel(R) Xeon(R) Gold 6242 CPU @ 2.80GHz GenuineIntel
> GNU/Linux
> Machine Type: x86_64-pc-linux-gnu
>
> Bash Version: 5.2
> Patch Level: 26
> Release Status: release
>
> Description:
> I have tried to write a bash script that asynchronously reads from
> a pipe (line by line) with the help of "read -t".
> If the timeout occurs in just the right moment, read returns the full
> line, but the return code says timeout (rc > 128).
> Therefor it is not possible to know if a full line was returned or
> not. Please see the script in the Repeat-By section that reproduces the
> error in seconds.
>
>
> Repeat-By:
> function reader() {
> local buf line
> while :; do
> read -t .01 buf
> rc=$?
> if (( rc == 0 )); then
> line+=$buf
> elif (( rc > 128 )); then
> line+=$buf
> continue
> fi
> [[ $line != TEST ]] && echo Invalid line: $line && exit
> echo OK
> line=""
> done
> }
> reader < <(
> while :; do
> echo -n TEST
> sleep .00$(($RANDOM%10))
> echo
> done
> )
>
>
