From 3b431a3c9071d3e654e66a461e152c6bf8386096 Mon Sep 17 00:00:00 2001 From: Kevin Buettner Date: Fri, 10 Mar 2023 15:27:43 -0700 Subject: [PATCH] PR gdb/30219: Clear sync_quit_force_run in quit_force PR 30219 shows an internal error due to a "Bad switch" in print_exception() in gdb/exceptions.c. The switch in question contains cases for RETURN_QUIT and RETURN_ERROR, but is missing a case for the recently added RETURN_FORCED_QUIT. This commit adds that case. Making the above change allows the errant test case to pass, but does not fix the underlying problem, which I'll describe shortly. Even though the addition of a case for RETURN_FORCED_QUIT isn't the actual fix, I still think it's important to add this case so that other situations which lead to print_exeption() being called won't generate that "Bad switch" internal error. In order to understand the underlying problem, please examine this portion of the backtrace from the bug report: 0x5576e4ff5780 print_exception /home/smarchi/src/binutils-gdb/gdb/exceptions.c:100 0x5576e4ff5930 exception_print(ui_file*, gdb_exception const&) /home/smarchi/src/binutils-gdb/gdb/exceptions.c:110 0x5576e6a896dd quit_force(int*, int) /home/smarchi/src/binutils-gdb/gdb/top.c:1849 The real problem is in quit_force; here's the try/catch which eventually leads to the internal error: /* Get out of tfind mode, and kill or detach all inferiors. */ try { disconnect_tracing (); for (inferior *inf : all_inferiors ()) kill_or_detach (inf, from_tty); } catch (const gdb_exception &ex) { exception_print (gdb_stderr, ex); } While running the calls in the try-block, a QUIT check is being performed. This check finds that sync_quit_force_run is (still) set, causing a gdb_exception_forced_quit to be thrown. The exception gdb_exception_forced_quit is derived from gdb_exception, causing exception_print to be called. As shown by the backtrace, print_exception is then called, leading to the internal error. The actual fix, also implemented by this commit, is to clear sync_quit_force_run along with the quit flag. This will allow the various cleanup code, called by quit_force, to run without triggering a gdb_exception_forced_quit. (Though, if another SIGTERM is sent to the gdb process, these flags will be set again and a QUIT check in the cleanup code will detect it and throw the exception.) Bug: https://sourceware.org/bugzilla/show_bug.cgi?id=30219 Approved-By: Simon Marchi --- gdb/exceptions.c | 1 + gdb/top.c | 8 ++++++++ 2 files changed, 9 insertions(+) diff --git a/gdb/exceptions.c b/gdb/exceptions.c index 4ab8dce58de..8b7858578a9 100644 --- a/gdb/exceptions.c +++ b/gdb/exceptions.c @@ -90,6 +90,7 @@ print_exception (struct ui_file *file, const struct gdb_exception &e) switch (e.reason) { case RETURN_QUIT: + case RETURN_FORCED_QUIT: annotate_quit (); break; case RETURN_ERROR: diff --git a/gdb/top.c b/gdb/top.c index aa2a6409d98..81f74f72f61 100644 --- a/gdb/top.c +++ b/gdb/top.c @@ -1824,6 +1824,14 @@ quit_force (int *exit_arg, int from_tty) { int exit_code = 0; + /* Clear the quit flag and sync_quit_force_run so that a + gdb_exception_forced_quit isn't inadvertently triggered by a QUIT + check while running the various cleanup/exit code below. Note + that the call to 'check_quit_flag' clears the quit flag as a side + effect. */ + check_quit_flag (); + sync_quit_force_run = false; + /* An optional expression may be used to cause gdb to terminate with the value of that expression. */ if (exit_arg) -- 2.30.2