Dandling memory pointers in Ada catchpoints with GDB/MI.

When using the GDB/MI commands to insert a catchpoint on a specific
Ada exception, any re-evaluation of that catchpoint (for instance
a re-evaluation performed after a shared library got mapped by the
inferior) fails. For instance, with any Ada program:

    (gdb)
    -catch-exception -e program_error
    ^done,bkptno="1",bkpt={[...]}
    (gdb)
    -exec-run
    =thread-group-started,id="i1",pid="28315"
    =thread-created,id="1",group-id="i1"
    ^running
    *running,thread-id="all"
    (gdb)
    =library-loaded,[...]
    &"warning: failed to reevaluate internal exception condition for catchpoint 1: No definition of \"exec\" in current context.\n"
    &"warning: failed to reevaluate internal exception condition for catchpoint 1: No definition of \"exec\" in current context.\n"
    [...]

The same is true if using an Ada exception catchpoint.

The problem comes from the fact that that we deallocate the strings
given as arguments to create_ada_exception_catchpoint, while the latter
just makes shallow copies of those strings, thus creating dandling
pointers.

This patch fixes the issue by passing freshly allocated strings to
create_ada_exception_catchpoint, while at the same time updating
create_ada_exception_catchpoint's documentation to make it clear
that deallocating the strings is no longer the responsibility of
the caller.

gdb/ChangeLog:

        * ada-lang.c (create_ada_exception_catchpoint): Enhance
        the documentation of fields "except_string" and "condition".
        * mi/mi-cmd-catch.c (mi_cmd_catch_assert): Reallocate
        CONDITION on the heap before passing it to
        create_ada_exception_catchpoint.
        (mi_cmd_catch_exception): Likewise for EXCEPTION_NAME and
        CONDITION.

gdb/testsuite/ChangeLog:

        * gdb.ada/mi_ex_cond: New testcase.

Tested on x86_64-linux.  The "-break-list" test FAILs without
this patch.

1 files changed, 10 insertions, 0 deletions

diff --git a/gdb/mi/mi-cmd-catch.c b/gdb/mi/mi-cmd-catch.c
index 23e30d0..bcfc1ba 100644
--- a/gdb/mi/mi-cmd-catch.c
+++ b/gdb/mi/mi-cmd-catch.c
@@ -81,6 +81,10 @@ mi_cmd_catch_assert (char *cmd, char *argv[], int argc)
     error (_("Invalid argument: %s"), argv[oind]);
 
   setup_breakpoint_reporting ();
+  /* create_ada_exception_catchpoint needs CONDITION to be xstrdup'ed,
+     and will assume control of its lifetime.  */
+  if (condition != NULL)
+    condition = xstrdup (condition);
   create_ada_exception_catchpoint (gdbarch, ada_catch_assert,
 				   NULL, condition, temp, enabled, 0);
 }
@@ -154,6 +158,12 @@ mi_cmd_catch_exception (char *cmd, char *argv[], int argc)
     error (_("\"-e\" and \"-u\" are mutually exclusive"));
 
   setup_breakpoint_reporting ();
+  /* create_ada_exception_catchpoint needs EXCEPTION_NAME and CONDITION
+     to be xstrdup'ed, and will assume control of their lifetime.  */
+  if (exception_name != NULL)
+    exception_name = xstrdup (exception_name);
+  if (condition != NULL)
+    condition = xstrdup (condition);
   create_ada_exception_catchpoint (gdbarch, ex_kind,
 				   exception_name, condition,
 				   temp, enabled, 0);