configure: Really use local libfdt if the system one is too old

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 <f4bug@amsat.org>
Message-Id: <20180415230522.24404-2-f4bug@amsat.org>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Reviewed-by: Thomas Huth <thuth@redhat.com>

diff --git a/configure b/configure
index 83a6080bf864113f6cf9bfe08b14fe4545308390..e25e0d9494e298a9f73d18831af997a9a5d059a7 100755 (executable)
--- a/configure
+++ b/configure
@@ -3804,7 +3804,8 @@ 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." \
@@ -5746,6 +5747,7 @@ 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"
 
 echo "Install prefix    $prefix"
@@ -5776,6 +5778,7 @@ 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            $python"
@@ -6710,6 +6713,7 @@ else
 fi
 echo "LDFLAGS=$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 93a07027b0a9e4b998d43c410c577ba8dc466106..04c7f74d0786f5df332f8b2c38bc04d49ce6c2bd 100644 (file)
--- 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)$@")