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Re: [PATCH] fix null pointer in mtrace

From: Florian Weimer <fweimer at redhat dot com>
To: liqingqing <liqingqing3 at huawei dot com>
Cc: Liusirui <liusirui at huawei dot com>, <libc-alpha at sourceware dot org>, <carlos at redhat dot com>, <siddhesh at gotplt dot org>, <dj at redhat dot com>, <hushiyuan at huawei dot com>
Date: Tue, 12 Nov 2019 11:41:51 +0100
Subject: Re: [PATCH] fix null pointer in mtrace
References: <1573550539-34259-1-git-send-email-liusirui@huawei.com> <fcd6b190-6e21-040b-edea-4c91377be814@huawei.com>

* liqingqing:

> I had tested this scenario, it seems like that the fprintf and other
> file operation function do not check the invalid argument like the
> null pointer.  does any one knows why fprintf do not check the input?

It's not required by the standard because violating preconditions
results in undefined behavior.  Sloppily written code with such bugs
tends to not check error returns from functions, either.  This means if
we added a null check for the stream argument to fprintf (e.g., failing
with EINVAL in that case), it would only obscure the problem and make
diagnosis even more difficult.

Thanks,
Florian

Follow-Ups:
- Re: [PATCH] fix null pointer in mtrace
  - From: liqingqing

References:
- [PATCH] fix null pointer in mtrace
  - From: Liusirui
- Re: [PATCH] fix null pointer in mtrace
  - From: liqingqing

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