Message-ID: <CALECgPbe1fNZ=XYA8A6Pypg1R8Uc7aVFcbA8uhqHLBRV09E8bA@mail.gmail.com>
Date: 2024-12-13T18:08:27Z
From: Brad Eck
Subject: [R-pkg-devel] truncating strings on purpose
In-Reply-To: <20241211162930.38eb4ba3@arachnoid>
Hi Ivan, List,
Thanks for the suggestion, and for the pointer on duplicating the error.
The good news is that I am able to trigger the warning locally now. The bad
news is that following the gcc docs on avoid the warning did not seem to
work:
gcc -std=gnu99 -fsanitize=undefined -fno-omit-frame-pointer -std=gnu11
-I"/usr/local/lib/R/include" -DNDEBUG -I/usr/local/include
-fsanitize=address
-O2 -Wstringop-truncation -fPIC -g -O2 -c input2.c -o input2.o
input2.c: In function ?inperrmsg?:
input2.c:863:5: warning: ?strncpy? output may be truncated copying 225
bytes from a string of length 255 [-Wstringop-truncation]
863 | strncpy(trunc_tok, tok, sizeof trunc_tok - 1);
| ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
I could also try memcpy, but i don't so much like the idea of going away
from string functions for string handling.
Other suggestions are also welcome.
Brad
On Wed, Dec 11, 2024 at 1:29?PM Ivan Krylov <ikrylov at disroot.org> wrote:
> ? Wed, 11 Dec 2024 12:12:11 +0000
> Brad Eck <bradleyjeck at gmail.com> ?????:
>
> > Found the following significant warnings:
> > input2.c:863:5: warning: ?__builtin_strncpy? output may be
> > truncated copying 225 bytes from a string of length 255
> > [-Wstringop-truncation]
>
> > Where the truncation warnings appear, I am truncating on purpose
> > using `strncpy` to avoid overflows later. I believe this works fine
> > from an application point of view but the warnings remain.
>
> GCC documentation suggests setting the length argument to _one less_
> than sizeof destination buffer in addition to terminating the string:
>
> https://gcc.gnu.org/onlinedocs/gcc-14.2.0/gcc/Warning-Options.html#index-Wstringop-truncation
>
> strncpy(trunc_s1, s1, sizeof trunc_s1 - 1);
> trunc_s1[sizeof trunc_s1 - 1] = '\0';
>
> --
> Best regards,
> Ivan
>
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