linux-kernel - New -Werror=restrict error with incremental gcc

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Message-ID: <34478c69-e238-90db-bf1e-9622a060c778@redhat.com>
Date:   Wed, 14 Mar 2018 14:19:41 -0700
From:   Laura Abbott <labbott@...hat.com>
To:     Arnaldo Carvalho de Melo <acme@...hat.com>,
        Adrian Hunter <adrian.hunter@...el.com>,
        Jiri Olsa <jolsa@...nel.org>,
        Namhyung Kim <namhyung@...nel.org>,
        Wang Nan <wangnan0@...wei.com>,
        Josh Poimboeuf <jpoimboe@...hat.com>
Cc:     Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: New -Werror=restrict error with incremental gcc

Hi,

Fedora picked up a new gcc (8.0.1-0.18.fc29) and it seems to have introduced a new error:

   gcc -Wp,-MD,/home/labbott/linux/tools/objtool/.str_error_r.o.d -Wp,-MT,/home/labbott/linux/tools/objtool/str_error_r.o -Wall -Werror -Wbad-function-cast -Wdeclaration-after-statement -Wformat-security -Wformat-y2k -Winit-self -Wmissing-declarations -Wmissing-prototypes -Wnested-externs -Wno-system-headers -Wold-style-definition -Wpacked -Wredundant-decls -Wshadow -Wstrict-prototypes -Wswitch-default -Wswitch-enum -Wundef -Wwrite-strings -Wformat -Wstrict-aliasing=3 -Wno-switch-default -Wno-switch-enum -Wno-packed -fomit-frame-pointer -O2 -g -I/home/labbott/linux/tools/include -I/home/labbott/linux/tools/arch/x86/include/uapi -I/home/labbott/linux/tools/objtool/arch/x86/include -I/home/labbott/linux/tools/lib -D"BUILD_STR(s)=#s" -c -o /home/labbott/linux/tools/objtool/str_error_r.o ../lib/str_error_r.c
../lib/str_error_r.c: In function ‘str_error_r’:
../lib/str_error_r.c:25:3: error: passing argument 1 to restrict-qualified parameter aliases with argument 5 [-Werror=restrict]
    snprintf(buf, buflen, "INTERNAL ERROR: strerror_r(%d, %p, %zd)=%d", errnum, buf, buflen, err);
    ^~

This looks like gcc is now warning about the aliasing from printing out buf
while printing to the buffer. I can work around this pretty easily but I
know people have strong opinions about gcc warnings. Any thoughts?

Thanks,
Laura