From: Steven Rostedt <rostedt@goodmis.org>
To: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Linux List Kernel Mailing <linux-kernel@vger.kernel.org>,
Ingo Molnar <mingo@kernel.org>,
Andrew Morton <akpm@linux-foundation.org>,
Namhyung Kim <namhyung@kernel.org>,
Masami Hiramatsu <mhiramat@kernel.org>,
Joe Perches <joe@perches.com>, Tom Zanussi <zanussi@kernel.org>,
Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Subject: Re: [for-next][PATCH 23/24] string.h: Add strncmp_prefix() helper macro
Date: Fri, 21 Dec 2018 18:03:48 -0500 [thread overview]
Message-ID: <20181221180348.766f7712@gandalf.local.home> (raw)
In-Reply-To: <CAHk-=wgSovEz3gy56q0bhOMVt9Rx5ooq97KmY=XX37_JdE+4pQ@mail.gmail.com>
On Fri, 21 Dec 2018 14:57:13 -0800
Linus Torvalds <torvalds@linux-foundation.org> wrote:
> On Fri, Dec 21, 2018 at 2:48 PM Steven Rostedt <rostedt@goodmis.org> wrote:
> >
> > > Your patch actually had them, but in the body of your email you did
> > >
> > > > #define have_prefix(str, prefix) ({ \
> > > > const char *__pfx = (const char *)prefix; \
> > >
> > > which is just completely wrong.
> > >
> > > Considering your _old_ patch had the exact same bug, I really think
> > > you need to start internalizing the whole "macro arguments *have* to
> > > be properly protected" thing.
> >
> > Well, there's less with assignments that can go wrong than with other
> > code. That is, there's little that can happen with "int x = arg;" where
> > arg is the macro paramater to cause something really nasty.
>
> What's wrong, Steven?
We are miscommunicating here...
I was talking about the missing parenthesis on the original patch,
which you stated was missing as well. And the original patch didn't
have the typecast.
>
> The assignment is entirely irrelevant.
>
> The problem is the cast.
>
> A type cast has a very high priority, and so if you do
>
> (const char *)prefix
>
> it breaks completely if you might have something like"a+6" as the argument.
>
> Think about what if "a" is of type "unsigned long", for example?
Yes, when writing the real code, I noticed that the typecast could
cause issues without the parenthesis, and added them.
The email you are replying to was saying there's not much that can go
wrong with:
#define MACRO(x) { \
int __p = x; \
I definitely can see something wrong with:
#define MACRO(x) { \
int __p = (int)x; \
because exactly what you stated.
There's nothing wrong with adding (x) for the first one, but it's
unlikely anything will cause it harm. The second one the (x) *is* most
definitely required.
This is a long winded "I agree with you" ;-)
-- Steve
next prev parent reply other threads:[~2018-12-21 23:03 UTC|newest]
Thread overview: 54+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-12-21 17:56 [for-next][PATCH 00/24] tracing: Updates for the next (coming soon) merge window Steven Rostedt
2018-12-21 17:56 ` [for-next][PATCH 01/24] ftrace: Allow ftrace_replace_code() to be schedulable Steven Rostedt
2018-12-21 17:56 ` [for-next][PATCH 02/24] arm64: ftrace: Set FTRACE_MAY_SLEEP before ftrace_modify_all_code() Steven Rostedt
2018-12-21 17:56 ` [for-next][PATCH 03/24] fgraph: Add comment to describe ftrace_graph_get_ret_stack Steven Rostedt
2018-12-21 17:56 ` [for-next][PATCH 04/24] x86/ftrace: Do not call function graph from dynamic trampolines Steven Rostedt
2018-12-21 17:56 ` [for-next][PATCH 05/24] powerpc/frace: Use ftrace_graph_get_ret_stack() instead of curr_ret_stack Steven Rostedt
2018-12-22 9:51 ` Michael Ellerman
2018-12-22 12:24 ` Steven Rostedt
2018-12-21 17:56 ` [for-next][PATCH 06/24] sparc64: " Steven Rostedt
2018-12-21 18:24 ` David Miller
2018-12-21 19:29 ` Steven Rostedt
2018-12-21 17:56 ` [for-next][PATCH 07/24] sh: ftrace: " Steven Rostedt
2018-12-21 17:56 ` [for-next][PATCH 08/24] arm64: " Steven Rostedt
2018-12-21 17:56 ` [for-next][PATCH 10/24] seq_buf: Use size_t for len in seq_buf_puts() Steven Rostedt
2018-12-21 17:56 ` [for-next][PATCH 11/24] tracing: Fix ftrace_graph_get_ret_stack() to use task and not current Steven Rostedt
2018-12-21 17:56 ` [for-next][PATCH 12/24] tracing: Remove unnecessary hist trigger struct field Steven Rostedt
2018-12-21 17:56 ` [for-next][PATCH 13/24] tracing: Change strlen to sizeof for hist trigger static strings Steven Rostedt
2018-12-21 17:56 ` [for-next][PATCH 14/24] tracing: Use var_refs[] for hist trigger reference checking Steven Rostedt
2018-12-21 17:56 ` [for-next][PATCH 15/24] tracing: Remove open-coding of hist trigger var_ref management Steven Rostedt
2018-12-21 17:56 ` [for-next][PATCH 16/24] tracing: Use hist triggers var_ref array to destroy var_refs Steven Rostedt
2018-12-21 17:56 ` [for-next][PATCH 17/24] tracing: Remove hist trigger synth_var_refs Steven Rostedt
2018-12-21 17:56 ` [for-next][PATCH 18/24] tracing: Add hist trigger comments for variable-related fields Steven Rostedt
2018-12-21 17:56 ` [for-next][PATCH 19/24] tracing: Merge seq_print_sym_short() and seq_print_sym_offset() Steven Rostedt
2018-12-21 17:56 ` [for-next][PATCH 21/24] tracing: Simplify printfing in seq_print_sym Steven Rostedt
2018-12-21 17:56 ` [for-next][PATCH 23/24] string.h: Add strncmp_prefix() helper macro Steven Rostedt
2018-12-21 18:51 ` Linus Torvalds
2018-12-21 19:40 ` Steven Rostedt
2018-12-21 20:01 ` Linus Torvalds
2018-12-21 20:35 ` Steven Rostedt
2018-12-21 20:46 ` Joe Perches
2018-12-21 20:54 ` Steven Rostedt
2018-12-21 20:58 ` Andreas Schwab
2018-12-21 21:08 ` Steven Rostedt
2018-12-21 22:20 ` Joe Perches
2018-12-21 22:29 ` Linus Torvalds
2018-12-21 22:58 ` Steven Rostedt
2018-12-21 22:55 ` Steven Rostedt
2018-12-23 22:01 ` Rasmus Villemoes
2018-12-23 22:56 ` Steven Rostedt
2018-12-23 23:52 ` Rasmus Villemoes
2018-12-24 0:05 ` Steven Rostedt
2018-12-23 23:01 ` Joe Perches
2018-12-21 20:58 ` Steven Rostedt
[not found] ` <CAHk-=wjtkvFUuRNZU67KccuUKYHw=pYoDMQJ_9OVDFxOwmK9zQ@mail.gmail.com>
2018-12-21 20:55 ` Steven Rostedt
2018-12-21 22:08 ` Linus Torvalds
2018-12-21 22:48 ` Steven Rostedt
2018-12-21 22:57 ` Linus Torvalds
2018-12-21 23:03 ` Steven Rostedt [this message]
2018-12-22 10:20 ` Malcolm Priestley
2018-12-22 12:26 ` Steven Rostedt
2018-12-21 17:56 ` [for-next][PATCH 24/24] tracing: Use strncmp_prefix() helper for histogram code Steven Rostedt
[not found] ` <20181221175656.827708767@goodmis.org>
2018-12-21 18:00 ` [for-next][PATCH 09/24] seq_buf: Make seq_buf_puts() null-terminate the buffer Steven Rostedt
2018-12-21 18:05 ` Steven Rostedt
2018-12-27 5:25 ` Michael Ellerman
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20181221180348.766f7712@gandalf.local.home \
--to=rostedt@goodmis.org \
--cc=akpm@linux-foundation.org \
--cc=gregkh@linuxfoundation.org \
--cc=joe@perches.com \
--cc=linux-kernel@vger.kernel.org \
--cc=mhiramat@kernel.org \
--cc=mingo@kernel.org \
--cc=namhyung@kernel.org \
--cc=torvalds@linux-foundation.org \
--cc=zanussi@kernel.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).