linux-kernel - Re: [PATCH v2 1/2] jump_label: Explicitly disable jump labels in _

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Date:   Sun, 18 Feb 2018 14:15:38 +0100
From:   Ingo Molnar <mingo@...nel.org>
To:     Thomas Gleixner <tglx@...utronix.de>
Cc:     Josh Poimboeuf <jpoimboe@...hat.com>, x86@...nel.org,
        linux-kernel@...r.kernel.org, Steven Rostedt <rostedt@...dmis.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Jason Baron <jbaron@...mai.com>, Borislav Petkov <bp@...e.de>
Subject: Re: [PATCH v2 1/2] jump_label: Explicitly disable jump labels in
 __init code


* Ingo Molnar <mingo@...nel.org> wrote:

> 2) code robustness 
> 
> For example:
> 
>         for (i = 0; i < 10; i++)
>                 if (foo)
>                         bar(i);
>                 baz(i);
> 
> Is probably buggy code, although technically it's valid syntax and will compile 
> just fine.
> 
> If all multi-line statements have curly braces then this type of bug cannot occur:
> 
>         for (i = 0; i < 10; i++) {
>                 if (foo)
>                         bar(i);
>                 baz(i);
> 	}

Note that newer versions of GCC will warn about this pattern:

     warning: this ‘for’ clause does not guard
              this statement, but the latter is misleadingly indented as if it were guarded by the ‘for’

But the warning is pretty restrictive and GCC won't warn about slightly more 
complex patterns like:

          for (i = 0; i < 10; i++)
                  if (foo)
                          bar(i);
//                debug_fn();
                  baz(i);

Thanks,

	Ingo