[RFA] Fix leaks in ada catch command
Philippe Waroquiers
philippe.waroquiers@skynet.be
Tue Feb 12 21:55:00 GMT 2019
On Tue, 2019-02-12 at 14:35 -0700, Tom Tromey wrote:
> > > > > > "Philippe" == Philippe Waroquiers <philippe.waroquiers@skynet.be> writes:
>
> Philippe> Fix the first leak by xfree-ing the addr_string allocated by ada_exception_sal.
> Philippe> Fix the second leak by calling the base bp_location dtor.
>
> Philippe> Tested on debian/amd64, natively and under valgrind.
>
> Thanks.
>
> Philippe> - const char *addr_string = NULL;
> Philippe> + char *addr_string = NULL;
> Philippe> const struct breakpoint_ops *ops = NULL;
> Philippe> - struct symtab_and_line sal = ada_exception_sal (ex_kind, &addr_string, &ops);
> Philippe> + struct symtab_and_line sal = ada_exception_sal (ex_kind,
> Philippe> + (const char **) &addr_string,
> Philippe> + &ops);
>
> This cast seems questionable to me -- and since ada_exception_sal is
> only called from this one spot, it seems like it would be just as
> simple, but also more clear and more obviously correct to simply change
> the type of "addr_string" to "std::string *". This would also avoid any
> potential leak if find_function_start_sal can throw (I didn't check).
>
> Philippe> static void
> Philippe> -bp_location_dtor (struct bp_location *self)
> Philippe> +base_bp_location_dtor (struct bp_location *self)
> Philippe> {
> Philippe> xfree (self->function_name);
> Philippe> }
>
> For this part, I think it's easy in this case to just further C++-ify
> bp_location. I've done this in the appended -- let me know what you
> think.
>
> Tom
Yes, your suggestions to use std::string * and the below patch seem
better to me. So, I assume you will push fixes for both
Thanks
Philippe
>
> commit 65a60067205f97696a91dd7f134013ffa112dc21
> Author: Tom Tromey <tromey@adacore.com>
> Date: Tue Feb 12 14:28:07 2019 -0700
>
> C++-ify bp_location
>
> Philippe noticed a memory leak coming from ada_catchpoint_location --
> it was not freeing the "function_name" member from its base class.
>
> This patch fixes the problem by further C++-ifying bp_location. In
> particular, bp_location_ops is now removed, and the "dtor" function
> pointer is replaced with an ordinary destructor.
>
> gdb/ChangeLog
> 2019-02-12 Tom Tromey <tom@tromey.com>
>
> * breakpoint.c (~bp_location): Rename from bp_location_dtor.
> (bp_location_ops): Remove.
> (base_breakpoint_allocate_location): Update.
> (free_bp_location): Update.
> * ada-lang.c (class ada_catchpoint_location)
> <ada_catchpoint_location>: Remove ops parameter.
> (ada_catchpoint_location_dtor): Remove.
> (ada_catchpoint_location_ops): Remove.
> (allocate_location_exception): Update.
> * breakpoint.h (struct bp_location_ops): Remove.
> (class bp_location) <bp_location>: Remove bp_location_ops
> parameter.
> <~bp_location>: Add destructor.
> <ops>: Remove.
>
> diff --git a/gdb/ChangeLog b/gdb/ChangeLog
> index 194ae465769..a773943b8e8 100644
> --- a/gdb/ChangeLog
> +++ b/gdb/ChangeLog
> @@ -1,3 +1,20 @@
> +2019-02-12 Tom Tromey <tom@tromey.com>
> +
> + * breakpoint.c (~bp_location): Rename from bp_location_dtor.
> + (bp_location_ops): Remove.
> + (base_breakpoint_allocate_location): Update.
> + (free_bp_location): Update.
> + * ada-lang.c (class ada_catchpoint_location)
> + <ada_catchpoint_location>: Remove ops parameter.
> + (ada_catchpoint_location_dtor): Remove.
> + (ada_catchpoint_location_ops): Remove.
> + (allocate_location_exception): Update.
> + * breakpoint.h (struct bp_location_ops): Remove.
> + (class bp_location) <bp_location>: Remove bp_location_ops
> + parameter.
> + <~bp_location>: Add destructor.
> + <ops>: Remove.
> +
> 2019-02-12 Philippe Waroquiers <philippe.waroquiers@skynet.be>
>
> * symtab.h (struct minimal_symbol data_p): New const method.
> diff --git a/gdb/ada-lang.c b/gdb/ada-lang.c
> index a878d4d1af2..602facb35e7 100644
> --- a/gdb/ada-lang.c
> +++ b/gdb/ada-lang.c
> @@ -12396,8 +12396,8 @@ static std::string ada_exception_catchpoint_cond_string
> class ada_catchpoint_location : public bp_location
> {
> public:
> - ada_catchpoint_location (const bp_location_ops *ops, breakpoint *owner)
> - : bp_location (ops, owner)
> + ada_catchpoint_location (breakpoint *owner)
> + : bp_location (owner)
> {}
>
> /* The condition that checks whether the exception that was raised
> @@ -12406,24 +12406,6 @@ public:
> expression_up excep_cond_expr;
> };
>
> -/* Implement the DTOR method in the bp_location_ops structure for all
> - Ada exception catchpoint kinds. */
> -
> -static void
> -ada_catchpoint_location_dtor (struct bp_location *bl)
> -{
> - struct ada_catchpoint_location *al = (struct ada_catchpoint_location *) bl;
> -
> - al->excep_cond_expr.reset ();
> -}
> -
> -/* The vtable to be used in Ada catchpoint locations. */
> -
> -static const struct bp_location_ops ada_catchpoint_location_ops =
> -{
> - ada_catchpoint_location_dtor
> -};
> -
> /* An instance of this type is used to represent an Ada catchpoint. */
>
> struct ada_catchpoint : public breakpoint
> @@ -12493,7 +12475,7 @@ static struct bp_location *
> allocate_location_exception (enum ada_exception_catchpoint_kind ex,
> struct breakpoint *self)
> {
> - return new ada_catchpoint_location (&ada_catchpoint_location_ops, self);
> + return new ada_catchpoint_location (self);
> }
>
> /* Implement the RE_SET method in the breakpoint_ops structure for all
> diff --git a/gdb/breakpoint.c b/gdb/breakpoint.c
> index 67d83e6f465..9be99ff4efa 100644
> --- a/gdb/breakpoint.c
> +++ b/gdb/breakpoint.c
> @@ -6958,13 +6958,10 @@ adjust_breakpoint_address (struct gdbarch *gdbarch,
> }
> }
>
> -bp_location::bp_location (const bp_location_ops *ops, breakpoint *owner)
> +bp_location::bp_location (breakpoint *owner)
> {
> bp_location *loc = this;
>
> - gdb_assert (ops != NULL);
> -
> - loc->ops = ops;
> loc->owner = owner;
> loc->cond_bytecode = NULL;
> loc->shlib_disabled = 0;
> @@ -7033,7 +7030,6 @@ allocate_bp_location (struct breakpoint *bpt)
> static void
> free_bp_location (struct bp_location *loc)
> {
> - loc->ops->dtor (loc);
> delete loc;
> }
>
> @@ -12166,19 +12162,11 @@ say_where (struct breakpoint *b)
> }
> }
>
> -/* Default bp_location_ops methods. */
> -
> -static void
> -bp_location_dtor (struct bp_location *self)
> +bp_location::~bp_location ()
> {
> - xfree (self->function_name);
> + xfree (function_name);
> }
>
> -static const struct bp_location_ops bp_location_ops =
> -{
> - bp_location_dtor
> -};
> -
> /* Destructor for the breakpoint base class. */
>
> breakpoint::~breakpoint ()
> @@ -12191,7 +12179,7 @@ breakpoint::~breakpoint ()
> static struct bp_location *
> base_breakpoint_allocate_location (struct breakpoint *self)
> {
> - return new bp_location (&bp_location_ops, self);
> + return new bp_location (self);
> }
>
> static void
> diff --git a/gdb/breakpoint.h b/gdb/breakpoint.h
> index 8c8c66a8158..a91e3e334cf 100644
> --- a/gdb/breakpoint.h
> +++ b/gdb/breakpoint.h
> @@ -301,31 +301,19 @@ enum bp_loc_type
> bp_loc_other /* Miscellaneous... */
> };
>
> -/* This structure is a collection of function pointers that, if
> - available, will be called instead of performing the default action
> - for this bp_loc_type. */
> -
> -struct bp_location_ops
> -{
> - /* Destructor. Releases everything from SELF (but not SELF
> - itself). */
> - void (*dtor) (struct bp_location *self);
> -};
> -
> class bp_location
> {
> public:
> bp_location () = default;
>
> - bp_location (const bp_location_ops *ops, breakpoint *owner);
> + bp_location (breakpoint *owner);
> +
> + virtual ~bp_location ();
>
> /* Chain pointer to the next breakpoint location for
> the same parent breakpoint. */
> bp_location *next = NULL;
>
> - /* Methods associated with this location. */
> - const bp_location_ops *ops = NULL;
> -
> /* The reference count. */
> int refc = 0;
>
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