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From: Jeff King <peff@peff.net>
To: "Miriam R." <mirucam@gmail.com>
Cc: git <git@vger.kernel.org>
Subject: Re: [Outreachy] Return value before or after free()?
Date: Mon, 6 Jan 2020 16:30:51 -0500	[thread overview]
Message-ID: <20200106213051.GD980197@coredump.intra.peff.net> (raw)
In-Reply-To: <CAN7CjDDBA0ZoCG9aaQf5rg3gxqny=EjR6v6jE1mnxvUJQSF_0Q@mail.gmail.com>

On Mon, Jan 06, 2020 at 10:15:53PM +0100, Miriam R. wrote:

> in run-command.c file `exists_in_PATH()` function does this:
> 
> static int exists_in_PATH(const char *file)
> {
> char *r = locate_in_PATH(file);
> free(r);
> return r != NULL;
> }
> 
> I wonder if it is correct to do return r != NULL; after free(r);

It is technically undefined behavior according to the C standard, but I
think it would be hard to find an implementation where it was not
perfectly fine in practice.

Ref: http://c-faq.com/malloc/ptrafterfree.html

I'd probably leave it alone unless it is causing a problem (e.g., a
static analyzer complaining).

-Peff

  reply	other threads:[~2020-01-06 21:30 UTC|newest]

Thread overview: 7+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-01-06 21:15 [Outreachy] Return value before or after free()? Miriam R.
2020-01-06 21:30 ` Jeff King [this message]
2020-01-06 22:47   ` Jonathan Nieder
2020-01-06 23:34   ` Andreas Schwab
2020-01-07  1:08   ` brian m. carlson
2020-01-07  1:58     ` brian m. carlson
2020-01-07 20:40       ` Miriam R.

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