Libtool claims it does not support shared libraries during cross compilation

Question

I'm attempting to build the expat (2.0.0) XML parsing library for an ARM embedded machine running busybox 1.13, and during the ./configure, I get the error:

checking if libtool supports shared libraries... no

I've specified my gcc, g++, ar, ranlib, strip, etc and those all get found by the configure tool, and I've got the very latest libtool (2.4.2 at the time of this writing) running on Ubuntu 12.10, so why is it saying that libtool doesn't support shared libraries ? My configure command is :

./configure --host=arm --enable-shared CC=arm-none-linux-gnueabi-gcc CXX=arm-none-linux-gnueabi-g++ AR=arm-none-linux-gnueabi-ar RANLIB=arm-none-linux-gnueabi-ranlib STRIP=arm-none-linux-gnueabi-strip

... and the complete output of the call is :

    configure: WARNING: If you wanted to set the --build type, don't use --host.
    If a cross compiler is detected then cross compile mode will be used.
checking build system type... i686-pc-linux-gnu
checking host system type... arm-unknown-none
checking for arm-gcc... arm-none-linux-gnueabi-gcc
checking for C compiler default output file name... a.out
checking whether the C compiler works... yes
checking whether we are cross compiling... yes
checking for suffix of executables... 
checking for suffix of object files... o
checking whether we are using the GNU C compiler... yes
checking whether arm-none-linux-gnueabi-gcc accepts -g... yes
checking for arm-none-linux-gnueabi-gcc option to accept ANSI C... none needed
checking for a sed that does not truncate output... /bin/sed
checking for egrep... grep -E
checking for ld used by arm-none-linux-gnueabi-gcc... /usr/local/arm/arm-2007q1/arm-none-linux-gnueabi/bin/ld
checking if the linker (/usr/local/arm/arm-2007q1/arm-none-linux-gnueabi/bin/ld) is GNU ld... yes
checking for /usr/local/arm/arm-2007q1/arm-none-linux-gnueabi/bin/ld option to reload object files... -r
checking for BSD-compatible nm... nm
checking whether ln -s works... yes
checking how to recognise dependent libraries... unknown
checking how to run the C preprocessor... arm-none-linux-gnueabi-gcc -E
checking for ANSI C header files... yes
checking for sys/types.h... yes
checking for sys/stat.h... yes
checking for stdlib.h... yes
checking for string.h... yes
checking for memory.h... yes
checking for strings.h... yes
checking for inttypes.h... yes
checking for stdint.h... yes
checking for unistd.h... yes
checking dlfcn.h usability... yes
checking dlfcn.h presence... yes
checking for dlfcn.h... yes
checking for arm-g++... arm-none-linux-gnueabi-g++
checking whether we are using the GNU C++ compiler... yes
checking whether arm-none-linux-gnueabi-g++ accepts -g... yes
checking how to run the C++ preprocessor... arm-none-linux-gnueabi-g++ -E
checking for arm-g77... no
checking for arm-f77... no
checking for arm-xlf... no
checking for arm-frt... no
checking for arm-pgf77... no
checking for arm-fort77... no
checking for arm-fl32... no
checking for arm-af77... no
checking for arm-f90... no
checking for arm-xlf90... no
checking for arm-pgf90... no
checking for arm-epcf90... no
checking for arm-f95... no
checking for arm-fort... no
checking for arm-xlf95... no
checking for arm-ifc... no
checking for arm-efc... no
checking for arm-pgf95... no
checking for arm-lf95... no
checking for arm-gfortran... no
checking for g77... no
checking for f77... no
checking for xlf... no
checking for frt... no
checking for pgf77... no
checking for fort77... no
checking for fl32... no
checking for af77... no
checking for f90... no
checking for xlf90... no
checking for pgf90... no
checking for epcf90... no
checking for f95... no
checking for fort... no
checking for xlf95... no
checking for ifc... no
checking for efc... no
checking for pgf95... no
checking for lf95... no
checking for gfortran... no
checking whether we are using the GNU Fortran 77 compiler... no
checking whether  accepts -g... no
checking the maximum length of command line arguments... 32768
checking command to parse nm output from arm-none-linux-gnueabi-gcc object... ok
checking for objdir... .libs
checking for arm-ar... arm-none-linux-gnueabi-ar
checking for arm-ranlib... arm-none-linux-gnueabi-ranlib
checking for arm-strip... arm-none-linux-gnueabi-strip
checking if arm-none-linux-gnueabi-gcc supports -fno-rtti -fno-exceptions... no
checking for arm-none-linux-gnueabi-gcc option to produce PIC... -fPIC
checking if arm-none-linux-gnueabi-gcc PIC flag -fPIC works... yes
checking if arm-none-linux-gnueabi-gcc static flag -static works... yes
checking if arm-none-linux-gnueabi-gcc supports -c -o file.o... yes
checking whether the arm-none-linux-gnueabi-gcc linker (/usr/local/arm/arm-2007q1/arm-none-linux-gnueabi/bin/ld) supports shared libraries... yes
checking whether -lc should be explicitly linked in... no
checking dynamic linker characteristics... no
checking how to hardcode library paths into programs... immediate
checking whether stripping libraries is possible... yes
checking if libtool supports shared libraries... no
checking whether to build shared libraries... no
checking whether to build static libraries... yes
configure: creating libtool
appending configuration tag "CXX" to libtool
checking for ld used by arm-none-linux-gnueabi-g++... /usr/local/arm/arm-2007q1/arm-none-linux-gnueabi/bin/ld
checking if the linker (/usr/local/arm/arm-2007q1/arm-none-linux-gnueabi/bin/ld) is GNU ld... yes
checking whether the arm-none-linux-gnueabi-g++ linker (/usr/local/arm/arm-2007q1/arm-none-linux-gnueabi/bin/ld) supports shared libraries... no
checking for arm-none-linux-gnueabi-g++ option to produce PIC... -fPIC
checking if arm-none-linux-gnueabi-g++ PIC flag -fPIC works... yes
checking if arm-none-linux-gnueabi-g++ static flag -static works... yes
checking if arm-none-linux-gnueabi-g++ supports -c -o file.o... yes
checking whether the arm-none-linux-gnueabi-g++ linker (/usr/local/arm/arm-2007q1/arm-none-linux-gnueabi/bin/ld) supports shared libraries... no
checking dynamic linker characteristics... no
checking how to hardcode library paths into programs... immediate
appending configuration tag "F77" to libtool
checking for arm-gcc... (cached) arm-none-linux-gnueabi-gcc
checking whether we are using the GNU C compiler... (cached) yes
checking whether arm-none-linux-gnueabi-gcc accepts -g... (cached) yes
checking for arm-none-linux-gnueabi-gcc option to accept ANSI C... (cached) none needed
checking for a BSD-compatible install... /usr/bin/install -c
checking whether gcc accepts -fexceptions... yes
checking for ANSI C header files... (cached) yes
checking whether byte ordering is bigendian... no
checking for an ANSI C-conforming const... yes
checking for size_t... yes
checking for memmove... yes
checking for bcopy... yes
checking fcntl.h usability... yes
checking fcntl.h presence... yes
checking for fcntl.h... yes
checking for unistd.h... (cached) yes
checking for off_t... yes
checking for stdlib.h... (cached) yes
checking for unistd.h... (cached) yes
checking for getpagesize... yes
checking for working mmap... no
checking for an ANSI C99-conforming __func__... yes
configure: creating ./config.status
config.status: creating Makefile
config.status: creating expat_config.h
amarshall3@pg-oj-amarshall3:~/Sandbox/expat-2.0.0$ make
/bin/bash ./libtool --silent --mode=compile arm-none-linux-gnueabi-gcc -I./lib -I. -g -O2 -Wall -Wmissing-prototypes -Wstrict-prototypes -fexceptions -DHAVE_EXPAT_CONFIG_H   -o lib/xmlparse.lo -c lib/xmlparse.c
/bin/bash ./libtool --silent --mode=compile arm-none-linux-gnueabi-gcc -I./lib -I. -g -O2 -Wall -Wmissing-prototypes -Wstrict-prototypes -fexceptions -DHAVE_EXPAT_CONFIG_H   -o lib/xmltok.lo -c lib/xmltok.c
/bin/bash ./libtool --silent --mode=compile arm-none-linux-gnueabi-gcc -I./lib -I. -g -O2 -Wall -Wmissing-prototypes -Wstrict-prototypes -fexceptions -DHAVE_EXPAT_CONFIG_H   -o lib/xmlrole.lo -c lib/xmlrole.c
/bin/bash ./libtool --silent --mode=link arm-none-linux-gnueabi-gcc -I./lib -I. -g -O2 -Wall -Wmissing-prototypes -Wstrict-prototypes -fexceptions -DHAVE_EXPAT_CONFIG_H   -no-undefined -version-info 6:0:5 -rpath /usr/local/lib  -o libexpat.la lib/xmlparse.lo lib/xmltok.lo lib/xmlrole.lo
arm-none-linux-gnueabi-gcc -I./lib -I. -g -O2 -Wall -Wmissing-prototypes -Wstrict-prototypes -fexceptions -DHAVE_EXPAT_CONFIG_H   -o xmlwf/xmlwf.o -c xmlwf/xmlwf.c
arm-none-linux-gnueabi-gcc -I./lib -I. -g -O2 -Wall -Wmissing-prototypes -Wstrict-prototypes -fexceptions -DHAVE_EXPAT_CONFIG_H   -o xmlwf/xmlfile.o -c xmlwf/xmlfile.c
arm-none-linux-gnueabi-gcc -I./lib -I. -g -O2 -Wall -Wmissing-prototypes -Wstrict-prototypes -fexceptions -DHAVE_EXPAT_CONFIG_H   -o xmlwf/codepage.o -c xmlwf/codepage.c
arm-none-linux-gnueabi-gcc -I./lib -I. -g -O2 -Wall -Wmissing-prototypes -Wstrict-prototypes -fexceptions -DHAVE_EXPAT_CONFIG_H   -o xmlwf/readfilemap.o -c xmlwf/readfilemap.c
xmlwf/readfilemap.c: In function 'filemap':
xmlwf/readfilemap.c:65: warning: implicit declaration of function 'read'
xmlwf/readfilemap.c:69: warning: implicit declaration of function 'close'
/bin/bash ./libtool --silent --mode=link arm-none-linux-gnueabi-gcc -I./lib -I. -g -O2 -Wall -Wmissing-prototypes -Wstrict-prototypes -fexceptions -DHAVE_EXPAT_CONFIG_H    -o xmlwf/xmlwf xmlwf/xmlwf.o xmlwf/xmlfile.o xmlwf/codepage.o xmlwf/readfilemap.o libexpat.la

Could somebody please explain to me how configure determines whether libtool supports building shared libraries ?

Answer 1

From the output:

checking build system type... i686-pc-linux-gnu
checking host system type... arm-unknown-none
...
checking whether the arm-none-linux-gnueabi-gcc linker (/usr/local/arm/arm-2007q1/arm-none-linux-gnueabi/bin/ld) supports shared libraries... yes
...
checking if libtool supports shared libraries... no
checking whether to build shared libraries... no
checking whether to build static libraries... yes

Probably libtool is confused by your host flag: --host=arm, which to libtool is the same as --host=arm-unknown-none. Try --host=arm-none-linux instead. IIRC, arm-unknown-none is used by people who want to do non-RTOS (main loop) type stuff for MCUs and other embedded boards where there's no OS and everything is statically linked into an image. Your toolchain is built for Linux: arm-none-linux.