linux-kernel - Re: [PATCH 2/2] tools/nolibc/stdlib: only reference the external environ when inlined

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Date:   Wed, 23 Mar 2022 20:36:24 +0700
From:   Ammar Faizi <ammarfaizi2@...weeb.org>
To:     Willy Tarreau <w@....eu>, "Paul E . McKenney" <paulmck@...nel.org>
Cc:     linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/2] tools/nolibc/stdlib: only reference the external
 environ when inlined

On 3/23/22 2:18 PM, Willy Tarreau wrote:
> When building with gcc at -O0 we're seeing link errors due to the
> "environ" variable being referenced by getenv(). The problem is that
> at -O0 gcc will not inline getenv() and will not drop the external
> reference. One solution would be to locally declare the variable as
> weak, but then it would appear in all programs even those not using
> it, and would be confusing to users of getenv() who would forget to
> set environ to envp.
> 
> An alternate approach used in this patch consists in always inlining
> the outer part of getenv() that references this extern so that it's
> always dropped when not used. The biggest part of the function was
> now moved to a new function called _getenv() that's still not inlined
> by default.
> 
> Reported-by: Ammar Faizi <ammarfaizi2@...weeb.org>
> Signed-off-by: Willy Tarreau <w@....eu>
> ---

This one works nicely. I will resend my previous RFC after this one
lands in Paul's tree to avoid conflict.

Tested-by: Ammar Faizi <ammarfaizi2@...weeb.org>

Thanks!

-- 
Ammar Faizi