linux-kernel - Re: [PATCH] ftrace: shut up -Wcast-function-type warning for ftrace_ops_no

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Date:   Mon, 22 Mar 2021 18:00:40 -0400
From:   Steven Rostedt <rostedt@...dmis.org>
To:     Arnd Bergmann <arnd@...nel.org>
Cc:     Ingo Molnar <mingo@...hat.com>, Arnd Bergmann <arnd@...db.de>,
        "Peter Zijlstra (Intel)" <peterz@...radead.org>,
        Adrian Hunter <adrian.hunter@...el.com>,
        Tobias Klauser <tklauser@...tanz.ch>,
        Wei Yang <richard.weiyang@...ux.alibaba.com>,
        Chengming Zhou <zhouchengming@...edance.com>,
        "Naveen N. Rao" <naveen.n.rao@...ux.vnet.ibm.com>,
        "Paul E. McKenney" <paulmck@...nel.org>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] ftrace: shut up -Wcast-function-type warning for
 ftrace_ops_no_ops

On Mon, 22 Mar 2021 22:49:58 +0100
Arnd Bergmann <arnd@...nel.org> wrote:

> From: Arnd Bergmann <arnd@...db.de>
> 
> With 'make W=1', gcc warns about casts between incompatible function
> types:
> 
> kernel/trace/ftrace.c:128:31: error: cast between incompatible function types from 'void (*)(long unsigned int,  long unsigned int)' to 'void (*)(long unsigned int,  long unsigned int,  struct ftrace_ops *, struct ftrace_regs *)' [-Werror=cast-function-type]
>   128 | #define ftrace_ops_list_func ((ftrace_func_t)ftrace_ops_no_ops)
>       |                               ^
> 
> As the commet here explains, this one was intentional, so shut up the
> warning harder by using a double cast.

Bonus points for reading the comment ;-)

I'll take this patch for the next merge window, thanks!

-- Steve