Fix GDB 8.3 regression crash when registers cannot be modified.

This crash was detected when using GDB with the valgrind gdbserver.
To reproduce:

valgrind sleep 10000

In another window:
gdb
target remote | vgdb
p printf("make sleep print something\n")
=>
terminate called after throwing an instance of 'gdb_exception_RETURN_MASK_ERROR'
Aborted

The problem is that the valgrind gdbserver does not allow to change
registers when the inferior is blocked in a system call.
GDB then raises an exception.  The exception causes the destructor
of
 typedef std::unique_ptr<infcall_suspend_state, infcall_suspend_state_deleter>
    infcall_suspend_state_up;
to be called.  This destructor itself tries to restore the value of
the registers, and fails similarly.  We must catch the exception in
the destructor to avoid crashing GDB.
If the destructor encounters a problem, no warning is produced if
there is an uncaught exception, as in this case, the user will already
be informed of a problem via this exception.

With this change, no crash anymore, and all the valgrind 3.15 tests
pass succesfully.

Note: when this patch is approved, I will push an equivalent patch
on master, but with TRY/CATCH/e.message () replaced by
try/catch/e.what ().

gdb/ChangeLog
2019-04-19  Philippe Waroquiers  <philippe.waroquiers@skynet.be>

	* inferior.h (struct infcall_suspend_state_deleter):
	Catch exception in destructor to avoid crash.

diff --git a/gdb/ChangeLog b/gdb/ChangeLog
index 44e0e1e..8a4da98 100644 (file)
--- a/gdb/ChangeLog
+++ b/gdb/ChangeLog
@@ -1,3 +1,8 @@
+2019-04-19  Philippe Waroquiers  <philippe.waroquiers@skynet.be>
+
+       * inferior.h (struct infcall_suspend_state_deleter):
+       Catch exception in destructor to avoid crash.
+
 2019-04-12  Eli Zaretskii  <eliz@gnu.org>
 
        * utils.c (prompt_for_continue): Don't restore the styling at the

diff --git a/gdb/inferior.h b/gdb/inferior.h
index 2d1bb97..4d84afa 100644 (file)
--- a/gdb/inferior.h
+++ b/gdb/inferior.h
@@ -68,7 +68,19 @@ struct infcall_suspend_state_deleter
 {
   void operator() (struct infcall_suspend_state *state) const
   {
-    restore_infcall_suspend_state (state);
+    TRY
+      {
+       restore_infcall_suspend_state (state);
+      }
+    CATCH (e, RETURN_MASK_ALL)
+      {
+       /* If we are restoring the inferior state due to an exception,
+          some error message will be printed.  So, only warn the user
+          when we cannot restore during normal execution.  */
+       if (!std::uncaught_exception ())
+         warning (_("Failed to restore inferior state: %s"), e.message);
+      }
+    END_CATCH
   }
 };