runtime/cgo: allow external library to register its own signal handler? #4216
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this issue is difficult to fix. libreadline registered a signal handler of its own. however, when the signal comes, it runs on Go's segmented stack, and it will surely crash. one possible solution is that we export our own sigaction and signal and override libc version of these two functions so that we can use cgo bridge to call that signal handler on C stack. |
Yes I can disable readline's signal handling and do the processing manually. Also, readline provides e.g. cleanup functions I can call to process SIGINT correctly, in particular to restore the terminal attributes. It might take a bit more work to have the readline() call return to the caller in Go (while in C doing fclose(stdin) is enough). Also, from the perspective of a readline binding package, it would be nice to emulate the default readline behavior of catching SIGINT, doing the cleanup and resending the signal. However this would require support from the os/signal package to temporarily remove existing SIGINT handlers (with the current API one can only add a handler, which results in a race condition if another SIGINT handler calls os.Exit() before cleanup is done). |
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Issue #5287 has been merged into this issue. |
> Go's signal handlers must not be overridden. I don't see any way around this. As this has come up yet again via issue #7227, I have to question this. Why not use kqueue with signal filters on the BSDs and use signalfd() on Linux? That'd allow Go to receive the signals no matter what the handler happen to be set to by 3rdparties. |
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A call to C.readline() from the GNU Readline library crashes when SIGWINCH is received. Running the following program: package main // #cgo LDFLAGS: -lreadline // #include <readline/readline.h> import "C" func main() { C.readline(C.CString("> ")) } And resizing the terminal gives this panic: > panic: runtime error: invalid memory address or nil pointer dereference [signal 0xb code=0x1 addr=0x1c pc=0x7f1a7644a3c5] goroutine 2 [syscall]: created by runtime.main /home/knuesel/repos/go/src/pkg/runtime/proc.c:221 goroutine 1 [syscall]: main._Cfunc_readline(0x3ee2010, 0x203e00000002) jnk/test/_obj/_cgo_defun.c:42 +0x2f main.main() jnk/test/_obj/test.cgo1.go:10 +0x3a Here is the backtrace from GDB: Program received signal SIGSEGV, Segmentation fault. 0x00007ffff7bc23c5 in ?? () from /lib/libreadline.so.6 (gdb) bt #0 0x00007ffff7bc23c5 in ?? () from /lib/libreadline.so.6 #1 <signal handler called> #2 runtime.futex () at /home/knuesel/repos/go/src/pkg/runtime/sys_linux_amd64.s:238 #3 0x000000000040d7e1 in runtime.futexsleep (addr=void, val=void, ns=void) at /home/knuesel/repos/go/src/pkg/runtime/thread_linux.c:62 #4 0x0000000000403a87 in runtime.notetsleep (n=void, ns=void) at /home/knuesel/repos/go/src/pkg/runtime/lock_futex.c:146 #5 0x0000000000407f18 in runtime.MHeap_Scavenger () at /home/knuesel/repos/go/src/pkg/runtime/mheap.c:363 #6 0x00000000004093ea in schedunlock () at /home/knuesel/repos/go/src/pkg/runtime/proc.c:267 #7 0x0000000000000000 in ?? () Which compiler are you using (5g, 6g, 8g, gccgo)? 6g Which operating system are you using? Ubuntu lucid Which version are you using? (run 'go version') 1.0.3 Please provide any additional information below. Tested with readline 5 and readline 6The text was updated successfully, but these errors were encountered: