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From: James Y Knight <jyknight@google.com>
To: musl@lists.openwall.com
Cc: Rich Felker <dalias@libc.org>, Ismael Luceno <ismael@iodev.co.uk>
Subject: Re: [musl] [RFC PATCH] implement strndupa
Date: Fri, 21 Oct 2022 18:09:42 -0400	[thread overview]
Message-ID: <CAA2zVHpQ3iuq_UydEJ0E3G-pvTvtu6v7KHeo8MSGw5JEb4JS8Q@mail.gmail.com> (raw)
In-Reply-To: <20221021211720.16465-1-ismael@iodev.co.uk>

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>
>  #define        strdupa(x)      strcpy(alloca(strlen(x)+1),x)
> +#define        strndupa(x, n)  strlcpy(alloca(strnlen((x), (n)), (x), (n))


This causes the parameters to be evaluated multiple times -- and that is
also a problem with the existing strdupa. Unfortunately it's impossible to
implement these macros without multiple-evaluation, unless you use the GCC
statement-expression language extension (as glibc does).

IMO, musl should either use that extension, despite the general policy of
avoiding such non-standard language extensions, or simply not implement
these functions at all. Implementing them, but having them incorrectly
multiply-evaluate the parameters seems like the worst of the options...

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  reply	other threads:[~2022-10-21 22:10 UTC|newest]

Thread overview: 3+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-10-21 21:17 Ismael Luceno
2022-10-21 22:09 ` James Y Knight [this message]
2022-10-22  0:26   ` Rich Felker

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