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gcc-9 stricter on NULL arguments for printf #2879

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ingvarha opened this issue Jan 9, 2019 · 1 comment

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commented Jan 9, 2019

I got the following bug report for Fedora.

Note that gcc-9 is not available readily wrapped for fedora yet, this is only a pre warning, so I have not had the opportunity to dig into this yet myself. There are only some 8 calls to printf in vnum.c (varnish-6.1.1), so it should not be too difficult to track this down, I guess.

Ingvar

From: Jeff Law law@redhat.com
Subject: Preparing for gcc-9 upgrade in Fedora -- your package is going to fail to build

I'm writing you because you have a package that will fail to build in Fedora once the compiler team drops in gcc-9.

In particular your package is calling one of the printf family of routines with a %s directive and a NULL argument for that directive. gcc-9 is better at discovering these than prior GCC versions.
(...)
varnish:

BUILDSTDERR: In file included from /usr/include/stdio.h:867,
BUILDSTDERR: from vnum.c:36:
BUILDSTDERR: In function 'printf',
BUILDSTDERR: inlined from 'main' at vnum.c:356:4:
BUILDSTDERR: /usr/include/bits/stdio2.h:107:10: error: '%s' directive argument is null [-Werror=format-overflow=]
BUILDSTDERR: 107 | return __printf_chk (__USE_FORTIFY_LEVEL - 1, __fmt, __va_arg_pack ());
BUILDSTDERR: | ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
BUILDSTDERR: cc1: all warnings being treated as errors

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commented Jan 11, 2019

In general I do not consider {"%s", NULL} an error, it is well established practice and very convenient i testing and debugging contexts like this one.

Have fixed it anyway, as I found the code could be simplified at the same time.

@bsdphk bsdphk closed this in 7119d79 Jan 11, 2019

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