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Fix debug Linux #679

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Fix debug Linux #679

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44a2441
Fix debug Linux
yuxiaomao Apr 22, 2024
20c19bb
Fix detect on exit
yuxiaomao May 2, 2024
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17 changes: 14 additions & 3 deletions src/std/debug.c
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Original file line number Diff line number Diff line change
Expand Up @@ -25,6 +25,7 @@
# include <sys/wait.h>
# include <sys/user.h>
# include <signal.h>
# include <errno.h>
# define USE_PTRACE
#endif

Expand Down Expand Up @@ -84,6 +85,7 @@ HL_API bool hl_debug_stop( int pid ) {
# elif defined(MAC_DEBUG)
return mdbg_session_detach(pid);
# elif defined(USE_PTRACE)
kill(pid, SIGTRAP); // DETACH needs ptrace-stop
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I think SIGSTOP would be more appropriate here.

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I agree. But when I test with SIGSTOP, the disconnect does not works properly (maybe SIGSTOP is not actually stopping - the signal is forward to our thread? or has some delay / different behavior than SIGTRAP). :(

return ptrace(PTRACE_DETACH,pid,0,0) >= 0;
# else
return false;
Expand Down Expand Up @@ -248,14 +250,23 @@ HL_API int hl_debug_wait( int pid, int *thread, int timeout ) {
return mdbg_session_wait(pid, thread, timeout);
# elif defined(USE_PTRACE)
int status;
int ret = waitpid(pid,&status,0);
//printf("WAITPID=%X %X\n",ret,status);
// *** HACK ***
// usleep here is needed for a good result.
// Without it, waitpid can miss many stop event;
// With it, and more we wait, less we miss stop event.
usleep(100 * 1000);
int ret = waitpid(pid, &status, WNOHANG);
Comment on lines +253 to +258
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I suspect that waitpid with WNOHANG is also vulnerable to a race condition with libuv.

I'm not sure how to fix this other than by doing the same thread & semaphore dance as the Mac debugger.

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I also suspect the waitpid hack was for libuv (or vscode) waiting for all childs.

I tested your implementation with thread (it helps me a lot!), but it failed when we are actually waiting (by default the vscode extension call wait with a timeout = 0) and has a timeout. I didn't managed to get it works yet :'(
You said @ncannasse refused your PR due to complexity, so I tried this hack. I will do the thread & semaphore if hack is not a good option either.

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That was another PR, I never actually submitted the thread & semaphore implementation.

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Sorry I misunderstood :(

if( ret == -1 && errno == ECHILD ) {
*thread = pid;
return 0;
}
*thread = ret;
if( ret <= 0 )
return -1;
if( WIFEXITED(status) )
return 0;
if( WIFSTOPPED(status) ) {
int sig = WSTOPSIG(status);
//printf(" STOPSIG=%d\n",sig);
if( sig == SIGSTOP || sig == SIGTRAP )
return 1;
return 3;
Expand Down