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    SubjectRe: New -Werror=restrict error with incremental gcc
    Em Wed, Mar 14, 2018 at 02:19:41PM -0700, Laura Abbott escreveu:
    > 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?

    I couldn't reproduce it here:

    [perfbuilder@b34646cdb12b perf]$ gcc -v
    Using built-in specs.
    COLLECT_GCC=gcc
    COLLECT_LTO_WRAPPER=/usr/libexec/gcc/x86_64-redhat-linux/8/lto-wrapper
    OFFLOAD_TARGET_NAMES=nvptx-none
    OFFLOAD_TARGET_DEFAULT=1
    Target: x86_64-redhat-linux
    Configured with: ../configure --enable-bootstrap
    --enable-languages=c,c++,objc,obj-c++,fortran,ada,go,lto --prefix=/usr
    --mandir=/usr/share/man --infodir=/usr/share/info
    --with-bugurl=http://bugzilla.redhat.com/bugzilla --enable-shared
    --enable-threads=posix --enable-checking=release --enable-multilib
    --with-system-zlib --enable-__cxa_atexit --disable-libunwind-exceptions
    --enable-gnu-unique-object --enable-linker-build-id
    --with-gcc-major-version-only --with-linker-hash-style=gnu
    --enable-plugin --enable-initfini-array --with-isl --enable-libmpx
    --enable-offload-targets=nvptx-none --without-cuda-driver
    --enable-gnu-indirect-function --with-tune=generic --with-arch_32=i686
    --build=x86_64-redhat-linux
    Thread model: posix
    gcc version 8.0.1 20180310 (Red Hat 8.0.1-0.17) (GCC)
    [perfbuilder@b34646cdb12b perf]$ rpm -q gcc
    gcc-8.0.1-0.17.fc29.x86_64
    [perfbuilder@b34646cdb12b perf]$

    [perfbuilder@b34646cdb12b perf]$ make O=/tmp/build/kernel/
    make[1]: Entering directory '/tmp/build/kernel'
    CHK include/config/kernel.release
    Using /git/perf as source for kernel
    GEN ./Makefile
    CHK include/generated/uapi/linux/version.h
    CHK include/generated/utsrelease.h
    CHK include/generated/bounds.h
    CHK include/generated/timeconst.h
    CHK include/generated/asm-offsets.h
    CALL /git/perf/scripts/checksyscalls.sh
    DESCEND objtool
    CC /tmp/build/kernel/tools/objtool/str_error_r.o
    LD /tmp/build/kernel/tools/objtool/objtool-in.o
    LINK /tmp/build/kernel/tools/objtool/objtool
    CHK scripts/mod/devicetable-offsets.h
    HOSTCC scripts/asn1_compiler


    :-\

    But I noticed some of those warnings and started action on then for
    tools/perf, things like:

    "perf annotate: Use asprintf when formatting objdump command line"

    https://git.kernel.org/pub/scm/linux/kernel/git/acme/linux.git/commit/?id=f22ed8ad2ca0

    - Arnaldo

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