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Re: [platform-testers] texinfo-6.6.90 pretest


From: Bruno Haible
Subject: Re: [platform-testers] texinfo-6.6.90 pretest
Date: Tue, 20 Aug 2019 23:09:05 +0200
User-agent: KMail/5.1.3 (Linux/4.4.0-157-generic; KDE/5.18.0; x86_64; ; )

Eli Zaretskii wrote:
> > > One other issue is that GCC 8 flags many uses of strncat in
> > > install-info.c as unsafe:
> > > 
> > >      install-info.c: In function 'split_entry':
> > >      install-info.c:1624:17: warning: 'strncat' specified bound 2 equals 
> > > source length [-Wstringop-overflow=]
> > >                       strncat (*description, "  ", 2);
> > >                       ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> > > 
> > 
> > The warnings are clearly pointless, because the amount of memory
> > allocated for *description is unknown to the compiler.
> > 
> > Which GCC options did you specify?
> 
> I didn't specify any options, the options in effect were those that
> the Texinfo build system specifies.

Strange. On a glibc system, I get different results:

* With gcc 8.3.0, no warnings in install-info.c.

* With gcc 9.2.0, just one warning:

In file included from /usr/include/string.h:630,
                 from ../gnulib/lib/string.h:41,
                 from ../../system.h:34,
                 from ../../install-info/install-info.c:18:
../../install-info/install-info.c: In function 'split_entry.constprop':
../../install-info/install-info.c:1634:11: warning: '__builtin_strncat' output 
truncated before terminating nul copying as many bytes from a string as its 
length [-Wstringop-truncation]
 1634 |           strncat (*description, ptr, length);
      |           ^~~~~~~
../../install-info/install-info.c:1633:27: note: length computed here
 1633 |           size_t length = strlen (ptr);
      |                           ^~~~~~~~~~~~

And it mentions -Wstringop-truncation, not -Wstringop-overflow, like you said.

Bruno




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