breakpoints/19546: Fix crash after updating breakpointsgdb-7.11-branchpoint

One of the last checks update_breakpoints_after_exec does while looping
over the list of breakpoints is check that the breakpoint has a valid
location spec. It uses event_location_empty_p to check if the location spec
is "empty", and if it is, the breakpoint is deleted.

momentary_breakpoint types rely on setting the breakpoint structure's
location spec to NULL, thereby causing an update to delete the breakpoint.
However, event_location_empty_p assumed that locations were never NULL.
As a result, GDB would crash dereferencing a NULL pointer whenever
update_breakpoints_after_exec would encounter a momentary_breakpoint.

This patch creates a new wrapper/helper function which tests that the given
breakpoint's location spec is non-NULL and if it is not "empty"
or "unspecified."

gdb/ChangeLog

	PR breakpoints/19546
	* breakpoint.c (breakpoint_event_location_empty_p): New function.
	(update_breakpoints_after_exec, bkpt_re_set): Use this new function
	instead of event_location_empty_p.

gdb/testsuite/ChangeLog

	PR breakpoints/19546
	* gdb.base/infcall-exec.c: New file.
	* gdb.base/infcall-exec2.c: New file.
	* gdb.base/infcall-exec.exp: New file.

1 files changed, 10 insertions, 2 deletions

diff --git a/gdb/breakpoint.c b/gdb/breakpoint.c
index c059861..f99a7ab 100644
--- a/gdb/breakpoint.c
+++ b/gdb/breakpoint.c
@@ -3764,6 +3764,14 @@ create_exception_master_breakpoint (void)
     }
 }
 
+/* Does B have a location spec?  */
+
+static int
+breakpoint_event_location_empty_p (const struct breakpoint *b)
+{
+  return b->location != NULL && event_location_empty_p (b->location);
+}
+
 void
 update_breakpoints_after_exec (void)
 {
@@ -3878,7 +3886,7 @@ update_breakpoints_after_exec (void)
     /* Without a symbolic address, we have little hope of the
        pre-exec() address meaning the same thing in the post-exec()
        a.out.  */
-    if (event_location_empty_p (b->location))
+    if (breakpoint_event_location_empty_p (b))
       {
 	delete_breakpoint (b);
 	continue;
@@ -13063,7 +13071,7 @@ static void
 bkpt_re_set (struct breakpoint *b)
 {
   /* FIXME: is this still reachable?  */
-  if (event_location_empty_p (b->location))
+  if (breakpoint_event_location_empty_p (b))
     {
       /* Anything without a location can't be re-set.  */
       delete_breakpoint (b);