Question

I’m having trouble getting a sample program to link correctly (in this case against the ICU library). When I do ‘make’, everything builds fine. But when I run it, it says it can’t find one of the .so’s. I double checked they’re all installed in /usr/local/lib. What I discovered was it was looking in /usr/lib. If I symlink from there to there actual location, it works.

Why is my LIBPATHS being ignored or not used?

Here is the Makefile

CC = g++

INCPATHS = -I/usr/local/include

CFLAGS = -c -Wall $(INCPATHS)

LIBPATHS = -L/usr/local/lib/
LIBS = $(LIBPATHS) -licuio -licui18n -licuuc -licuio -licudata

EXECUTABLE = prog

print_linking = echo -e "\033[32m" "Linking: $<" "\033[39m"
print_compiling = echo -e "\033[33m" "Compiling: $<" "\033[39m"
print_cleaning = echo -e "\033[31m" "Cleaning: `pwd`" "\033[39m"


all: main

# [target]: [dependencies]
# <tab> system command
main: main.o
    @$(print_linking)
    @$(CC) -o $(EXECUTABLE) main.o $(LIBS) >> /dev/null

main.o: main.cpp
    @$(print_compiling)
    @$(CC) $(CFLAGS) main.cpp 

clean:
    @$(print_cleaning)
    @rm -rf *.o *~ $(EXECUTABLE)

Answer 1

Your LIBPATHS tells the linker where to find the library when linking to resolve symbols.

At runtime, you need to tell the loader where to find the library. It doesn’t know about what happened at compile time. You can use the LD_LIBRARY_PATH variable as mentioned above, or check into /etc/ld.so.conf and it’s friends.