From: John Baldwin <jhb@FreeBSD.org>
To: Tom Tromey <tom@tromey.com>, gdb-patches@sourceware.org
Subject: Re: [PATCH 6/6] Make aop_map 'static'
Date: Tue, 20 Jun 2023 08:39:31 -0700 [thread overview]
Message-ID: <a020c46d-505c-47f1-907b-8efa54ab61a0@FreeBSD.org> (raw)
In-Reply-To: <20230619-ax-new-v1-6-b26175d997a9@tromey.com>
On 6/19/23 2:06 PM, Tom Tromey wrote:
> This changes aop_map to be 'static'.
>
> It also changes a runtime assertion into a static assert. I'm not
> sure if this assert provides much value -- by construction, it can't
> really fail -- but it's clearly more useful as a static assert than a
> runtime one.
> ---
> gdb/ax-general.c | 40 +++++++++++++++++++++++++++++++++-------
> gdb/ax.h | 30 ------------------------------
> 2 files changed, 33 insertions(+), 37 deletions(-)
>
> diff --git a/gdb/ax-general.c b/gdb/ax-general.c
> index 7a37aff3d70..b1ee2753bd8 100644
> --- a/gdb/ax-general.c
> +++ b/gdb/ax-general.c
> @@ -294,7 +294,36 @@ ax_string (struct agent_expr *x, const char *str, int slen)
> /* Functions for disassembling agent expressions, and otherwise
> debugging the expression compiler. */
>
> -struct aop_map aop_map[] =
> +/* An entry in the opcode map. */
> +struct aop_map
> + {
> +
> + /* The name of the opcode. Null means that this entry is not a
> + valid opcode --- a hole in the opcode space. */
> + const char *name;
> +
> + /* All opcodes take no operands from the bytecode stream, or take
> + unsigned integers of various sizes. If this is a positive number
> + n, then the opcode is followed by an n-byte operand, which should
> + be printed as an unsigned integer. If this is zero, then the
> + opcode takes no operands from the bytecode stream.
> +
> + If we get more complicated opcodes in the future, don't add other
> + magic values of this; that's a crock. Add an `enum encoding'
> + field to this, or something like that. */
> + int op_size;
> +
> + /* The size of the data operated upon, in bits, for bytecodes that
> + care about that (ref and const). Zero for all others. */
> + int data_size;
> +
> + /* Number of stack elements consumed, and number produced. */
> + int consumed, produced;
> + };
> +
> +/* Map of the bytecodes, indexed by bytecode number. */
> +
> +static struct aop_map aop_map[] =
> {
> {0, 0, 0, 0, 0}
> #define DEFOP(NAME, SIZE, DATA_SIZE, CONSUMED, PRODUCED, VALUE) \
> @@ -303,6 +332,9 @@ struct aop_map aop_map[] =
> #undef DEFOP
> };
>
> +/* Check the size of the name array against the number of entries in
> + the enum, to catch additions that people didn't sync. */
> +gdb_static_assert ((sizeof (aop_map) / sizeof (aop_map[0])) == aop_last);
Maybe use ARRAY_SIZE here while you are at it?
Looking around in ax-general.c more, it seems we already do runtime
validation of potential indices before indexing the array, so I'm not sure
the assertion adds much value and I'd be tempted to remove aop_last entirely.
BTW, the various other places in ax-general.c that do the assertion are
all using the expanded form of ARRAY_SIZE and would be a bit more readable
perhaps if they used ARRAY_SIZE instead.
--
John Baldwin
next prev parent reply other threads:[~2023-06-20 15:39 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-06-19 21:06 [PATCH 0/6] C++-ify and simplify agent expressions Tom Tromey
2023-06-19 21:06 ` [PATCH 1/6] Remove mem2hex Tom Tromey
2023-06-19 21:06 ` [PATCH 2/6] Use gdb::byte_vector in agent_expr Tom Tromey
2023-06-19 21:06 ` [PATCH 3/6] Use std::vector<bool> for agent_expr::reg_mask Tom Tromey
2023-06-20 15:30 ` John Baldwin
2023-06-20 17:04 ` Tom Tromey
2023-06-19 21:06 ` [PATCH 4/6] Simplify agent_expr constructor Tom Tromey
2023-06-19 21:06 ` [PATCH 5/6] Use bool for agent_expr::tracing Tom Tromey
2023-06-20 15:31 ` John Baldwin
2023-06-20 17:04 ` Tom Tromey
2023-06-19 21:06 ` [PATCH 6/6] Make aop_map 'static' Tom Tromey
2023-06-20 15:39 ` John Baldwin [this message]
2023-06-20 17:12 ` Tom Tromey
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