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Bug #49314 cross compile fails to find dlopen, libdl, HAVE_DLOPEN, HAVE_LIBDL
Submitted: 2009-08-20 16:13 UTC Modified: 2009-08-21 11:37 UTC
Votes:5
Avg. Score:5.0 ± 0.0
Reproduced:5 of 5 (100.0%)
Same Version:2 (40.0%)
Same OS:2 (40.0%)
From: sbraun at emlix dot com Assigned:
Status: Wont fix Package: Dynamic loading
PHP Version: 5.3.0 OS: linux
Private report: No CVE-ID: None
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 [2009-08-20 16:13 UTC] sbraun at emlix dot com
Description:
------------
I cross compile libphp5.so in a i486-pc-linux-gnu chroot, the compiler is an i486-pc-linux-gnu-gcc that produces code for an i686-pc-linux-gnu target (the compile runs as part of an embedded systems build system).

When I load the libphp5.so into apache, it fails with:
httpd: Syntax error on line 54 of /etc/httpd/conf/httpd.conf: Cannot load /usr/lib/apache/libphp5.so into server: /usr/lib/apache/libphp5.so: undefined symbol: php_load_extension 

php_load_extension from dl.c is guarded by #ifdef HAVE_LIBDL

objdump -x libphp5.so:
00000000         *UND*  00000000              php_load_extension

In my cross_compile situtation, the #defines for dlopen and libdl are not set, thus HAVE_DLOPEN and HAVE_LIBDL are not in main/php_config.h, yet my system provides dlopen() via dl.so.

Naturally, dl.so is there in my chroot and provides dlopen(), and the configure script finds this fact when searching for dlopen() respectively __dlopen(), yet then it throws the findings away, the relevant lines in the configure script are:
------------------
  if test "$found" = "yes"; then
    ac_libs=$LIBS
    LIBS="$LIBS -ldl"
    if test "$cross_compiling" = yes; then
  found=no
else
------------------
Later, writing the #defines HAVE_DLOPEN and HAVE_LIBDL is guarded by: 
------------------
  if test "$found" = "yes"; then
------------------




Reproduce code:
---------------
autoconf configure.in > configure
build_platform=i486-pc-linux-gnu
target_platform=i486-pc-linux-gnu
PKG_CONFIG_PATH=${sysroot}/usr/lib/pkgconfig \
./configure \
        --prefix=${_prefix} \
        --build=${build_platform} \
        --host=${target_platform} \
        --target=${target_platform} \
        --mandir=${_mandir} \
        --with-apxs2="${sysroot}${_sbindir}/apxs" \
        --with-libxml-dir="${sysroot}${_prefix}" \
        --with-openssl \
        --without-iconv \
        --disable-cli \
        ;

start apache with a line in httpd.conf:
LoadModule php5_module /usr/lib/apache/libphp5.so

you get the error described above

Expected result:
----------------
well, it should load and stuff

Actual result:
--------------
Instead I will provide some bugfix suggestion:

I am not so much a friend of autoconf, so i think i am maybe not the right person to provide a patch directly. Maybe there is a reason for the behaviour. I am going to comment the problematic line out in my project, patch would be welcome.

# phps configure mysteriously refuses to use found libdl
#    if test "$cross_compiling" = yes; then
#  found=no

regards
Simon Braunschmidt


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 [2009-08-20 16:15 UTC] sbraun at emlix dot com
The compiler is an i686 compiler, which runs in an i486-pc-linux-gnu chroot. So the first lines should read:

I cross compile libphp5.so in a i486-pc-linux-gnu chroot, the compiler
is an i686-pc-linux-gnu-gcc that produces code for an i686-pc-linux-gnu
target (the compile runs as part of an embedded systems build system).
 [2009-08-21 11:37 UTC] jani@php.net
Unfortunately we don't support cross-compiling out-of-box. Best way to do this is to first generate rough template Makefile (which you bascally got already) and then manually fix the LIBS, and such.
 
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