Question

I have built a shared library (i.e libabc.so) and an executable (i.e myapp) which uses my shared library. I have placed both the shared library and my executable in my filesystem but when I run my executable it gives me the following error

error while loading shared libraries: <target_lib_path>/<mylib>.so cannot open shared object file: No such file or directory.

Now my dev environment is I have a different target filesystem which is placed at ~/targetfs after building my shared library I am installing it in ~/targetfs/usr/local/abc/lib. During linking my application I give it

LDFLAGS += -L~/targetfs/usr/local/abc/lib 

My application builds fine. But when I run my application in an environment where ~/targetfs is my filesystem, then my application complains
error while loading shared libraries:

/home/user/targetfs/usr/local/abc/lib/libabc.so: can not open shared object file. No such file or directory exist.

Now, of course the path my application is searching for the shared library that does not exist, but I want my application to be independent of this path, rather it should look for my shared library in /lib, /usr/lib, /usr/local/lib or LD_LIBRARY_PATH location.

How can I make my application to link libraries independent of its location?

Makefiles for my shared library & application is given below.

————– Shared library makefile. (Omitting un-necessary info)

CC              = $(CROSS_COMPILE)gcc
CFLAGS          = -Wall -shared -fpic
LDFLAGS         = -Xlinker --gc-sections --allow-shlib-undefined
LIBRARY         = libabc.so
OBJ_DIR         = obj
SRC_DIR         = src
CHK_DIR_EXISTS  = test -d
MKDIR           = mkdir -p

# Project Source Files
C_SOURCES += $(SRC_DIR)/abc.c
OBJECTS   += $(OBJ_DIR)/abc.o
INCLUDES  += -Iinc                               
$(LIBRARY): $(OBJECTS)
    @echo ""
    @echo "Linking..." $(LIBRARY)
    @$(CC) $(CFLAGS) $(LDFLAGS) $(OBJECTS) -o $(OBJ_DIR)/$(LIBRARY) 

———- Application Makefile (Omitting un-necessary info)

LDFLAGS += $(TARGETFS)/usr/local/abc/lib/libabc.so           \
       -lpthread -lrt

Any thoughts what’s missing in my Makefiles.

Answer 1

You can ask the linker to put multiple search paths into the binary. You introduce those search paths with the -Wl,rpath=… option.

gcc -o abc abc.c 
-L~/targetfs/usr/local/abc/lib 
-labc 
-Wl,-rpath=/usr/local/abc/lib 
-Wl,-rpath=...
-Wl,-rpath=...