| Message ID | 1398687662-27080-1-git-send-email-mst@redhat.com |
|---|---|
| State | New |
| Headers | show |
On 04/28/2014 06:21 AM, Michael S. Tsirkin wrote: > When source directory can be arrived at by two paths, > configure might misdetect an out of tree build. > The simplest way to trigger the problem is running > configure using a full path. E.g. (<firstpath> refers to qemu source > tree): > ln -s <firstpath> <secondpath> > cd <firstpath> > <secondpath>/configure > > A more practical way is when make runs configure automatically: > +# running configure in the source tree? create a temporary file > +# under pwd, check for it in source tree. Use .o suffix so that > +# make clean will blow it away if > +canary_path=`pwd` > +canary_fullpath=`mktemp "$canary_path/canary.XXXXXXXXXX.o"` mktemp is non-POSIX, and not necessarily portable. In particular, on FreeBSD, 'mktemp a.XXXX.b' generates the file 'a.XXXX.b', with no randomness introduced, which therefore makes it a predictable file name and defeats the purpose of using mktemp. Paolo's suggestion of using ./configure as the canary seems more reliable.
Eric Blake <eblake@redhat.com> writes: > On 04/28/2014 06:21 AM, Michael S. Tsirkin wrote: >> When source directory can be arrived at by two paths, >> configure might misdetect an out of tree build. >> The simplest way to trigger the problem is running >> configure using a full path. E.g. (<firstpath> refers to qemu source >> tree): >> ln -s <firstpath> <secondpath> >> cd <firstpath> >> <secondpath>/configure >> >> A more practical way is when make runs configure automatically: > >> +# running configure in the source tree? create a temporary file >> +# under pwd, check for it in source tree. Use .o suffix so that >> +# make clean will blow it away if >> +canary_path=`pwd` >> +canary_fullpath=`mktemp "$canary_path/canary.XXXXXXXXXX.o"` > > mktemp is non-POSIX, and not necessarily portable. In particular, on > FreeBSD, 'mktemp a.XXXX.b' generates the file 'a.XXXX.b', with no > randomness introduced, which therefore makes it a predictable file name > and defeats the purpose of using mktemp. > > Paolo's suggestion of using ./configure as the canary seems more reliable. For what it's worth, recommended autoconf practice is to use a source file that's probably unique to the package: -- Macro: AC_CONFIG_SRCDIR (UNIQUE-FILE-IN-SOURCE-DIR) UNIQUE-FILE-IN-SOURCE-DIR is some file that is in the package's source directory; `configure' checks for this file's existence to make sure that the directory that it is told contains the source code in fact does. Occasionally people accidentally specify the wrong directory with `--srcdir'; this is a safety check. *Note configure Invocation::, for more information. We got a bunch starting with qemu-; suggest to pick one you like.
diff --git a/configure b/configure index b08afc3..4a59cb7 100755 --- a/configure +++ b/configure @@ -404,6 +404,22 @@ fi # make source path absolute source_path=`cd "$source_path"; pwd` +# running configure in the source tree? create a temporary file +# under pwd, check for it in source tree. Use .o suffix so that +# make clean will blow it away if +canary_path=`pwd` +canary_fullpath=`mktemp "$canary_path/canary.XXXXXXXXXX.o"` +if test -z "$canary_fullpath"; then + error_exit "Current directory $canary_path/ does not appear to be writeable" +fi +canary_basename=`basename "$canary_fullpath"` +if test -e "$source_path/$canary_basename"; then + pwd_is_source_path="y" +else + pwd_is_source_path="n" +fi +rm -f -- "$canary_fullpath" + check_define() { cat > $TMPC <<EOF #if !defined($1) @@ -2940,7 +2956,7 @@ EOF fdt=yes dtc_internal="yes" mkdir -p dtc - if [ "$source_path" != `pwd` ] ; then + if [ "$pwd_is_source_path" != "y" ] ; then symlink "$source_path/dtc/Makefile" "dtc/Makefile" symlink "$source_path/dtc/scripts" "dtc/scripts" fi @@ -5178,7 +5194,7 @@ do done mkdir -p $DIRS for f in $FILES ; do - if [ -e "$source_path/$f" ] && [ "$source_path" != `pwd` ]; then + if [ -e "$source_path/$f" ] && [ "$pwd_is_source_path" != "y" ]; then symlink "$source_path/$f" "$f" fi done
When source directory can be arrived at by two paths, configure might misdetect an out of tree build. The simplest way to trigger the problem is running configure using a full path. E.g. (<firstpath> refers to qemu source tree): ln -s <firstpath> <secondpath> cd <firstpath> <secondpath>/configure A more practical way is when make runs configure automatically: 1. cd <firstpath>/; ./configure SRC_PATH=<firstpath>/ is written into config_host.mak 2. cd <secondpath>/; touch configure; make make now runs <firstpath>/configure, so configure assumes it's an out of tree build When this happens configure overwrites parts of the current tree with symlinks. Make the test more robust: create a canary file under the build tree, then look for it in the source tree. If there - we know it's a source build! Signed-off-by: Michael S. Tsirkin <mst@redhat.com> --- configure | 20 ++++++++++++++++++-- 1 file changed, 18 insertions(+), 2 deletions(-)