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, 9 insertions, 5 deletions

diff --git a/gdb/ada-lang.c b/gdb/ada-lang.c
index 4b55460..7817132 100644
--- a/gdb/ada-lang.c
+++ b/gdb/ada-lang.c
@@ -12170,11 +12170,15 @@ ada_exception_sal (enum ada_exception_catchpoint_kind ex, char *excep_string,
 
    EX_KIND is the kind of exception catchpoint to be created.
 
-   EXCEPT_STRING, if not NULL, indicates the name of the exception
-   to which this catchpoint applies.  If NULL, this catchpoint is
-   expected to trigger for all exceptions.
-
-   COND_STRING, if not NULL, is the catchpoint condition.
+   If EXCEPT_STRING is NULL, this catchpoint is expected to trigger
+   for all exceptions.  Otherwise, EXCEPT_STRING indicates the name
+   of the exception to which this catchpoint applies.  When not NULL,
+   the string must be allocated on the heap, and its deallocation
+   is no longer the responsibility of the caller.
+
+   COND_STRING, if not NULL, is the catchpoint condition.  This string
+   must be allocated on the heap, and its deallocation is no longer
+   the responsibility of the caller.
 
    TEMPFLAG, if nonzero, means that the underlying breakpoint
    should be temporary.