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Date: Tue, 12 Oct 2021 03:24:07 +0000
From: "(GalaxyMaster)" <>
Cc:, Kaihang Zhang <>
Subject: Re: [PATCH] fix: Assign default value to mntent when linebuf
 is too small


On Mon, Oct 11, 2021 at 10:36:43PM -0400, Kaihang Zhang wrote:
> Function getmntent_r in source misc/mntent.c will do what glibc users
> expect. The rest of the line will be discarded when can not be read
> into linebuf, and the fields of struct mntent will be assigned to empty
> string or zero when can not be found in linebuf, instead of setting
> errno to ERANGE and exiting.

Although this patch is on a similar topic as mine (changing the behaviour of
get*ent() funnctions), I think the change you are describing is considerable.

I would expect a function such as getmntent_r() which takes a user provided
buffer to fail and set ERANGE if the provided buffer is not enough to hold
the line.  This gives the developer an opportunity to recover, e.g. to
re-allocate a bigger buffer and try again.

In your proposal, I see two issues:

1. There is no feedback to the developer, so they have no idea whether the
   information they've got from the function was truncated or not (and what
   good does a truncated mnt line bring?);
2. There is no opportunity for the developer to realise a mistake they made
   by supplying too small buffer, hence there is no chance of recovering
   from it.

It is just my opinion and I would love to see other comments, since I have
not stumbled upon your use case yet and am not authoritative on this topic.


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