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Ignoring failures and altering behavior
- From: Florian Weimer <fweimer at redhat dot com>
- To: libc-alpha at sourceware dot org
- Date: Wed, 17 Oct 2018 12:36:47 +0200
- Subject: Ignoring failures and altering behavior
In many cases, glibc currently papers over resource allocation failures
by changing behavior. Some examples:
* If we cannot load a NSS service module with dlopen for any reason
(including malloc/mmap failures), we pretend that the service module
does not exist. NSS will possibly return different data as a result.
* If we cannot allocate memory for the gconv/iconv path, we will ignore
the user configuration and use a built-in path.
* If we cannot open /etc/host.conf for any reason, we do not report an
error and pretend that the file does not exist, possibly altering
name resolution results.
* If we get a read error indicating file system corruption or
unavailability for a directory in the dynamic linker, we ignore that
I'm sure there are many more examples.
File system errors can be quite tricky. I used this code in one case to
tell persistent, possibly intended errors from actual problems:
FILE *fp = fopen (_PATH_RESCONF, "rce");
if (fp == NULL)
/* Ignore these errors. They are persistent errors caused
by file system contents. */
/* Other errors refer to resource allocation problems and
need to be handled by the application. */
But I think there is a larger question here: Should we keep running at
all cost, possibly giving quite different results, or is it better to
actually report the errors we encounter and stop?