On 1/9/19 5:39 PM, Thomas Huth wrote:
> Different versions of GCC and Clang use different versions of the C standard.
> This repeatedly caused problems already, e.g. with duplicated typedefs:
>
> https://lists.gnu.org/archive/html/qemu-devel/2018-11/msg05829.html
>
> or with for-loop variable initializers:
>
> https://lists.gnu.org/archive/html/qemu-devel/2019-01/msg00237.html
>
> To avoid these problems, we should enforce the C language version to the
> same level for all compilers. Since our minimum compiler versions is
> GCC v4.8, our best option is "gnu99" for C code right now ("gnu17" is not
> available there yet, and "gnu11" is marked as "experimental"), and "gnu++98"
> for the few C++ code that we have in the repository.
>
> Signed-off-by: Thomas Huth <th...@redhat.com>
Raising from a 30 years old stantard to a 20 years old one is a great
improvement (I used to be a defender of the C89, but I evolved and now
admit C99 has helpful features).
Using '-std=gnu++98' for g++ v4.8 looks like a good compromise to the
issues Daniel mentioned (still 'experimental').
Reviewed-by: Philippe Mathieu-Daudé <phi...@redhat.com>
> ---
> v3: Compile C++ code with -std=gnu++98
>
> configure | 5 ++++-
> 1 file changed, 4 insertions(+), 1 deletion(-)
>
> diff --git a/configure b/configure
> index b9f34af..448dbc8 100755
> --- a/configure
> +++ b/configure
> @@ -107,6 +107,9 @@ update_cxxflags() {
> -Wstrict-prototypes|-Wmissing-prototypes|-Wnested-externs|\
> -Wold-style-declaration|-Wold-style-definition|-Wredundant-decls)
> ;;
> + -std=gnu99)
> + QEMU_CXXFLAGS=${QEMU_CXXFLAGS:+$QEMU_CXXFLAGS }"-std=gnu++98"
> + ;;
> *)
> QEMU_CXXFLAGS=${QEMU_CXXFLAGS:+$QEMU_CXXFLAGS }$arg
> ;;
> @@ -585,7 +588,7 @@ ARFLAGS="${ARFLAGS-rv}"
> # left shift of signed integers is well defined and has the expected
> # 2s-complement style results. (Both clang and gcc agree that it
> # provides these semantics.)
> -QEMU_CFLAGS="-fno-strict-aliasing -fno-common -fwrapv $QEMU_CFLAGS"
> +QEMU_CFLAGS="-fno-strict-aliasing -fno-common -fwrapv -std=gnu99
> $QEMU_CFLAGS"
> QEMU_CFLAGS="-Wall -Wundef -Wwrite-strings -Wmissing-prototypes $QEMU_CFLAGS"
> QEMU_CFLAGS="-Wstrict-prototypes -Wredundant-decls $QEMU_CFLAGS"
> QEMU_CFLAGS="-D_GNU_SOURCE -D_FILE_OFFSET_BITS=64 -D_LARGEFILE_SOURCE
> $QEMU_CFLAGS"
>
