Re: [Qemu-devel] [PATCH for-2.12? 1/4] configure: Really use local libfdt if the system one is too old

[Thomas Huth]

On 16.04.2018 01:05, Philippe Mathieu-Daudé wrote:
> QEMU requires libfdt version >= 1.4.2.
> If the host has an older libfdt installed, the configure script will use
> a (git cloned) local version.
> 
> Example with Debian 8:
>     $ dpkg-query --showformat='${Version}\n' --show libfdt-dev
>     1.4.0+dfsg-1
>     $ ./configure
>     [...]
>     fdt support       yes          # from git submodule 'dtc'
> 
> If this case occurs, the linker will have 2 different libfdt available in
> the library search path. The default behavior is to search the system path
> first, then the local path.
> 
> Even if the configure script noticed the libfdt is too old and clone a more
> recent locally, when linking the system library is selected first, and the
> link process eventually fails:
> 
>       LINK    mips64el-softmmu/qemu-system-mips64el
>     ../hw/core/loader-fit.o: In function `load_fit':
>     /root/src/github.com/philmd/qemu/hw/core/loader-fit.c:278: undefined 
> reference to `fdt_first_subnode'
>     /root/src/github.com/philmd/qemu/hw/core/loader-fit.c:286: undefined 
> reference to `fdt_next_subnode'
>     /root/src/github.com/philmd/qemu/hw/core/loader-fit.c:277: undefined 
> reference to `fdt_first_subnode'
>     collect2: error: ld returned 1 exit status
>     Makefile:201: recipe for target 'qemu-system-mips64el' failed
>     make[1]: *** [qemu-system-mips64el] Error 1
> 
> QEMU already uses a kludge to enforce local CFLAGS before system ones for
> libpixman and libfdt, add a similar kludge for the LDFLAGS to enforce using
> the local libfdt.
> 
> Signed-off-by: Philippe Mathieu-Daudé <address@hidden>
> ---
>  configure | 6 +++++-
>  rules.mak | 2 +-
>  2 files changed, 6 insertions(+), 2 deletions(-)
> 
> diff --git a/configure b/configure
> index 0a19b033bc..162e804b49 100755
> --- a/configure
> +++ b/configure
> @@ -3773,7 +3773,8 @@ EOF
>                symlink "$source_path/dtc/scripts" "dtc/scripts"
>            fi
>            fdt_cflags="-I\$(SRC_PATH)/dtc/libfdt"
> -          fdt_libs="-L\$(BUILD_DIR)/dtc/libfdt $fdt_libs"
> +          fdt_ldflags="-L\$(BUILD_DIR)/dtc/libfdt"
> +          fdt_libs="$fdt_libs"
>        elif test "$fdt" = "yes" ; then
>            # Not a git build & no libfdt found, prompt for system install
>            error_exit "DTC (libfdt) version >= 1.4.2 not present." \
> @@ -5715,6 +5716,7 @@ echo_version() {
>  
>  # prepend pixman and ftd flags after all config tests are done
>  QEMU_CFLAGS="$pixman_cflags $fdt_cflags $QEMU_CFLAGS"
> +QEMU_LDFLAGS="$fdt_ldflags $QEMU_LDFLAGS"
>  libs_softmmu="$pixman_libs $libs_softmmu"

I think the pixman lines could be removed now that we do not have an
internal pixman version anymore (but that's something for a separate patch)

>  echo "Install prefix    $prefix"
> @@ -5745,6 +5747,7 @@ echo "ARFLAGS           $ARFLAGS"
>  echo "CFLAGS            $CFLAGS"
>  echo "QEMU_CFLAGS       $QEMU_CFLAGS"
>  echo "LDFLAGS           $LDFLAGS"
> +echo "QEMU_LDFLAGS      $QEMU_LDFLAGS"
>  echo "make              $make"
>  echo "install           $install"
>  echo "python            $python"
> @@ -6679,6 +6682,7 @@ else
>  fi
>  echo "LDFLAGS=$LDFLAGS" >> $config_host_mak
>  echo "LDFLAGS_NOPIE=$LDFLAGS_NOPIE" >> $config_host_mak
> +echo "QEMU_LDFLAGS=$QEMU_LDFLAGS" >> $config_host_mak
>  echo "LD_REL_FLAGS=$LD_REL_FLAGS" >> $config_host_mak
>  echo "LD_I386_EMULATION=$ld_i386_emulation" >> $config_host_mak
>  echo "LIBS+=$LIBS" >> $config_host_mak
> diff --git a/rules.mak b/rules.mak
> index 93a07027b0..04c7f74d07 100644
> --- a/rules.mak
> +++ b/rules.mak
> @@ -73,7 +73,7 @@ expand-objs = $(strip $(sort $(filter %.o,$1)) \
>  # must link with the C++ compiler, not the plain C compiler.
>  LINKPROG = $(or $(CXX),$(CC))
>  
> -LINK = $(call quiet-command, $(LINKPROG) $(QEMU_CFLAGS) $(CFLAGS) $(LDFLAGS) 
> -o $@ \
> +LINK = $(call quiet-command, $(LINKPROG) $(QEMU_LDFLAGS) $(QEMU_CFLAGS) 
> $(CFLAGS) $(LDFLAGS) -o $@ \
>         $(call process-archive-undefs, $1) \
>         $(version-obj-y) $(call extract-libs,$1) 
> $(LIBS),"LINK","$(TARGET_DIR)$@")

Looks reasonable.

Reviewed-by: Thomas Huth <address@hidden>