[SOLVED] What happens when shared library not available?

littlebigman · 01-24-2011, 06:23 PM

Hello

I'm trying to investigate why Lua fails loading a module on an appliance running uClinux:

Code:

appliance> ./lua -l luasql.sqlite3
./lua: can't resolve symbol '_luaL_ref'

When running ldd on a workstation...

Code:

workstation#/opt/uClinux-2010/bfin-linux-uclibc/bin/bfin-linux-uclibc-ldd
/var/tmp/lua-5.1.4/src/lua

ldd: can't map cache '/etc/ld.so.cache'
checking sub-depends for 'not found'
checking sub-depends for 'not found'
checking sub-depends for '/lib/libgcc_s.so.1'
checking sub-depends for 'not found'
checking sub-depends for '/lib/libc.so.6'
        libdl.so.0 => not found (0x00000000)
        libm.so.0 => not found (0x00000000)
        libgcc_s.so.1 => /lib/libgcc_s.so.1 (0x00000000)
        libc.so.0 => not found (0x00000000)
        libc.so.6 => /lib/libc.so.6 (0x00000000)
        /lib/ld-linux.so.2 => /lib/ld-linux.so.2 (0x00000000)

... and then checking which libraries are available on the appliance...

Code:

appliance> find / -name "libdl.so.0"
/lib/libdl.so.0
appliance> find / -name "libm.so.0"
/lib/libm.so.0
appliance> find / -name "libgcc_s.so.1"
/lib/libgcc_s.so.1
appliance> find / -name "libc.so.0"
/lib/libc.so.0
appliance> find / -name "libc.so.6"
appliance> find / -name "ld-linux*"
appliance>

... it appears that a couple of them are missing.

Could those two missing shared libraries explain the issue I'm having?

Incidenty, is the source code for "ldd" available, so I can try cross-compiling and running it on the appliance?

Thank you.

reed9 · 01-25-2011, 11:10 AM

ldd is provided by the GNU C library (glibc). Source code is available.

Oliv' · 01-25-2011, 08:11 PM

Hello,

From my point of view your problem is not directly "ldd" related. The problem is that it does not find a symbol which should belongs to your binary or maybe to a liblua.so... In any case it probably means that something weird happens during cross-compilation. So if you could provide us more info about your cross-compilation steps and also tell us if you did some source code change, it may help to understand why you get this error.

Kind regards,

Oliv'

littlebigman · 01-26-2011, 03:50 AM

Thanks guys. It does look like a compile/linking issue, although no error occurs.

Here's what I did to compile the Lua interpreter, SQLite3, and LuaSQL + SQLite3:

Code:

# cat /var/tmp/lua-5.1.4/src/Makefile
export PATH:=$(PATH):/usr/src/baps/opt/uClinux/bfin-linux-uclibc/bin

TARGET_CROSS=bfin-linux-uclibc-
export CC=$(TARGET_CROSS)gcc
export STRIP=$(TARGET_CROSS)strip
export AR=$(TARGET_CROSS)ar rcu
export RANLIB=$(TARGET_CROSS)ranlib
export STAGING_DIR=/usr/src/baps/uClinux-dist/staging
export UCLINUX_LIB=/usr/src/baps/uClinux-dist/lib
export UCLINUX_ROOT_LIB=/usr/src/baps/uClinux-dist/root/lib
export CFLAGS=-O2 -Wall -Wmissing-prototypes -Wmissing-declarations -I$(STAGING_DIR)/usr/include -DLUA_USE_POSIX -DLUA_USE_DLOPEN
export LDFLAGS= -L$(STAGING_DIR)/usr/lib -L$(UCLINUX_LIB) -L$(UCLINUX_ROOT_LIB) -ldl -lm

...
$(LUA_T): $(LUA_O) $(LUA_A)
        $(CC) -o $@ $(CFLAGS) $(LDFLAGS) $(LUA_O) $(LUA_A)

$(LUAC_T): $(LUAC_O) $(LUA_A)
        $(CC) -o $@ $(CFLAGS) $(LDFLAGS) $(LUAC_O) $(LUA_A)
...
generic:
        $(MAKE) all

# cat /var/tmp/sqlite-amalgamation-3070400/Makefile
export PATH:=$(PATH):/usr/src/baps/opt/uClinux/bfin-linux-uclibc/bin

TARGET_CROSS=bfin-linux-uclibc-
export CC=$(TARGET_CROSS)gcc
export STRIP=$(TARGET_CROSS)strip
export AR=$(TARGET_CROSS)ar rcu
export RANLIB=$(TARGET_CROSS)ranlib
export CFLAGS=-O2 -Wall

libsqlite3.o:
        $(CC) $(CFLAGS) -DSQLITE_THREADSAFE=0 -o $@ -c sqlite3.c

# cat /var/tmp/luasql-2.1.1/config
...
LUA_INC= /var/tmp/lua-5.1.4/src
LIB_OPTION= -shared #for Linux
...
DRIVER_LIBS= /var/tmp/sqlite-amalgamation-3070400/libsqlite3.o
DRIVER_INCS= -I/var/tmp/sqlite-amalgamation-3070400

WARN= -Wall
INCS= -I$(LUA_INC)
CFLAGS= -O2 $(WARN) -I$(COMPAT_DIR) $(DRIVER_INCS) $(INCS) $(DEFS)
CC=/usr/src/baps/opt/uClinux/bfin-linux-uclibc/bin/bfin-linux-uclibc-gcc
LDFLAGS = -Wl,--trace,--print-map,--cref

# cat /var/tmp/luasql-2.1.1/Makefile
...
src/$(LIBNAME): $(OBJS)
        $(CC) $(CFLAGS) $(LDFLAGS) -o $@ $(OBJS) $(DRIVER_LIBS) $(LIB_OPTION)

Based on the error message, it looks like it's due to faulty compiling of Lua or LuaSocket, but I don't know how else to compile those two parts.

Thanks for any help.

littlebigman · 01-26-2011, 05:35 AM

After being told that it was most likely a linking issue, and after more reading and trial/error, I finally found what it was: When building Lua, the following options are required: "-Wl,-E"