g++ --std=c++11 -fPIC -fvisibility=hidden -c fooapi/foo.cpp -o fooapi/foo.o
g++ -fPIC -fvisibility=hidden -shared -Wl,-soname,libfoo.so.1.0.0 -o lib/libfoo.so.1.0.0 fooapi/foo.o
ldd lib/libfoo.so.1.0.0
linux-vdso.so.1 => (0x00007ffe0e12c000)
libstdc++.so.6 => /lib64/libstdc++.so.6 (0x00007fcf7f9dc000)
libm.so.6 => /lib64/libm.so.6 (0x00007fcf7f6da000)
libgcc_s.so.1 => /lib64/libgcc_s.so.1 (0x00007fcf7f4c4000)
libc.so.6 => /lib64/libc.so.6 (0x00007fcf7f0f7000)
/lib64/ld-linux-x86-64.so.2 (0x00007fcf7fee7000)
g++ --std=c++11 -fPIC -fvisibility=hidden -c fooapir2/foo.cpp -o fooapir2/foo.o
g++ -fPIC -fvisibility=hidden -shared -Wl,-soname,libfoo.so.1.0.2 -o lib/libfoo.so.1.0.2 fooapir2/foo.o
ldd lib/libfoo.so.1.0.*
lib/libfoo.so.1.0.0:
linux-vdso.so.1 => (0x00007fffc7d5d000)
libstdc++.so.6 => /lib64/libstdc++.so.6 (0x00007f467a3fc000)
libm.so.6 => /lib64/libm.so.6 (0x00007f467a0fa000)
libgcc_s.so.1 => /lib64/libgcc_s.so.1 (0x00007f4679ee4000)
libc.so.6 => /lib64/libc.so.6 (0x00007f4679b17000)
/lib64/ld-linux-x86-64.so.2 (0x00007f467a907000)
lib/libfoo.so.1.0.2:
linux-vdso.so.1 => (0x00007ffcc05fd000)
libstdc++.so.6 => /lib64/libstdc++.so.6 (0x00007f7968bfe000)
libm.so.6 => /lib64/libm.so.6 (0x00007f79688fc000)
libgcc_s.so.1 => /lib64/libgcc_s.so.1 (0x00007f79686e6000)
libc.so.6 => /lib64/libc.so.6 (0x00007f7968319000)
/lib64/ld-linux-x86-64.so.2 (0x00007f7969109000)
cd lib; ln -s libfoo.so.1.0.0 libfoo.so.1; ln -s libfoo.so.1 libfoo.so; cd ..
total 40
lrwxrwxrwx. 1 amd amd 11 Sep 4 11:30 libfoo.so -> libfoo.so.1
lrwxrwxrwx. 1 amd amd 15 Sep 4 11:30 libfoo.so.1 -> libfoo.so.1.0.0
-rwxrwxr-x. 1 amd amd 20120 Sep 4 11:16 libfoo.so.1.0.0
-rwxrwxr-x. 1 amd amd 20120 Sep 4 11:23 libfoo.so.1.0.2
g++ --std=c++11 -Ifooapi -fPIC -fvisibility=hidden -c barapi/bar.cpp -o barapi/bar.o
g++ -fPIC -fvisibility=hidden -shared -Wl,-soname,libbar.so.1.0.0 -o lib/libbar.so.1.0.0 barapi/bar.o
cd lib; ln -s libbar.so.1.0.0 libbar.so.1; ln -s libbar.so.1 libbar.so; cd ..
total 60
lrwxrwxrwx. 1 amd amd 11 Sep 4 11:37 libbar.so -> libbar.so.1
lrwxrwxrwx. 1 amd amd 15 Sep 4 11:37 libbar.so.1 -> libbar.so.1.0.0
-rwxrwxr-x. 1 amd amd 20160 Sep 4 11:34 libbar.so.1.0.0
lrwxrwxrwx. 1 amd amd 11 Sep 4 11:30 libfoo.so -> libfoo.so.1
lrwxrwxrwx. 1 amd amd 15 Sep 4 11:30 libfoo.so.1 -> libfoo.so.1.0.0
-rwxrwxr-x. 1 amd amd 20120 Sep 4 11:16 libfoo.so.1.0.0
-rwxrwxr-x. 1 amd amd 20120 Sep 4 11:23 libfoo.so.1.0.2
g++ --std=c++11 -Ifooapi -Ibarapi main.cpp -o main -Llib -lfoo -lbar
LD_LIBRARY_PATH=lib ldd ./main
linux-vdso.so.1 => (0x00007ffca29e4000)
libfoo.so.1.0.0 => lib/libfoo.so.1.0.0 (0x00007f5a8572a000)
libbar.so.1.0.0 => lib/libbar.so.1.0.0 (0x00007f5a85526000)
libstdc++.so.6 => /lib64/libstdc++.so.6 (0x00007f5a8521f000)
libm.so.6 => /lib64/libm.so.6 (0x00007f5a84f1d000)
libgcc_s.so.1 => /lib64/libgcc_s.so.1 (0x00007f5a84d07000)
libc.so.6 => /lib64/libc.so.6 (0x00007f5a8493a000)
/lib64/ld-linux-x86-64.so.2 (0x00007f5a8592e000)
Make libbar depend on libfoo - recompile libbar and main app
g++ -fPIC -fvisibility=hidden -shared -Wl,-soname,libbar.so.1.0.0 -o lib/libbar.so.1.0.0 barapi/bar.o -Llib -lfoo
ldd lib/libbar.so
linux-vdso.so.1 => (0x00007ffc5db8e000)
libfoo.so.1.0.0 => not found
libstdc++.so.6 => /lib64/libstdc++.so.6 (0x00007f82064d2000)
libm.so.6 => /lib64/libm.so.6 (0x00007f82061d0000)
libgcc_s.so.1 => /lib64/libgcc_s.so.1 (0x00007f8205fba000)
libc.so.6 => /lib64/libc.so.6 (0x00007f8205bed000)
/lib64/ld-linux-x86-64.so.2 (0x00007f82069dd000)
LD_LIBRARY_PATH=lib ldd lib/libbar.so
linux-vdso.so.1 => (0x00007fff7f1f5000)
libfoo.so.1.0.0 => lib/libfoo.so.1.0.0 (0x00007f3566b82000)
libstdc++.so.6 => /lib64/libstdc++.so.6 (0x00007f356687b000)
libm.so.6 => /lib64/libm.so.6 (0x00007f3566579000)
libgcc_s.so.1 => /lib64/libgcc_s.so.1 (0x00007f3566363000)
libc.so.6 => /lib64/libc.so.6 (0x00007f3565f96000)
/lib64/ld-linux-x86-64.so.2 (0x00007f3566f8a000)
g++ --std=c++11 -Ifooapi -Ibarapi main.cpp -o main -Llib -lbar
/usr/bin/ld: warning: libfoo.so.1.0.0, needed by lib/libbar.so, not found (try using -rpath or -rpath-link)
/tmp/ccPtxeEW.o: In function `main':
main.cpp:(.text+0xa): undefined reference to `foo'
collect2: error: ld returned 1 exit status
Use rpath to the rescue - recompile libbar telling loader to look in for dep libs
g++ -fPIC -fvisibility=hidden -shared -Wl,-soname,libbar.so.1.0.0 -Wl,-rpath,$ORIGIN -o lib/libbar.so.1.0.0 barapi/bar.o -Llib -lfoo
Dynamic section at offset 0x2d98 contains 30 entries:
Tag Type Name/Value
0x0000000000000001 (NEEDED) Shared library: [libfoo.so.1.0.0]
0x0000000000000001 (NEEDED) Shared library: [libstdc++.so.6]
0x0000000000000001 (NEEDED) Shared library: [libm.so.6]
0x0000000000000001 (NEEDED) Shared library: [libgcc_s.so.1]
0x0000000000000001 (NEEDED) Shared library: [libc.so.6]
0x000000000000000e (SONAME) Library soname: [libbar.so.1.0.0]
0x000000000000000f (RPATH) Library rpath: [$ORIGIN]
0x000000000000000c (INIT) 0x1560
0x000000000000000d (FINI) 0x2010
0x0000000000000019 (INIT_ARRAY) 0x202d68
0x000000000000001b (INIT_ARRAYSZ) 16 (bytes)
0x000000000000001a (FINI_ARRAY) 0x202d78
0x000000000000001c (FINI_ARRAYSZ) 8 (bytes)
0x000000006ffffef5 (GNU_HASH) 0x1f0
0x0000000000000005 (STRTAB) 0x830
0x0000000000000006 (SYMTAB) 0x2a8
0x000000000000000a (STRSZ) 1790 (bytes)
0x000000000000000b (SYMENT) 24 (bytes)
0x0000000000000003 (PLTGOT) 0x203000
0x0000000000000002 (PLTRELSZ) 960 (bytes)
0x0000000000000014 (PLTREL) RELA
0x0000000000000017 (JMPREL) 0x11a0
0x0000000000000007 (RELA) 0x1038
0x0000000000000008 (RELASZ) 360 (bytes)
0x0000000000000009 (RELAENT) 24 (bytes)
0x000000006ffffffe (VERNEED) 0xfa8
0x000000006fffffff (VERNEEDNUM) 3
0x000000006ffffff0 (VERSYM) 0xf2e
0x000000006ffffff9 (RELACOUNT) 4
0x0000000000000000 (NULL) 0x0
readelf -d main
Dynamic section at offset 0xdd8 contains 29 entries:
Tag Type Name/Value
0x0000000000000001 (NEEDED) Shared library: [libbar.so.1.0.0]
0x0000000000000001 (NEEDED) Shared library: [libfoo.so.1.0.0]
0x0000000000000001 (NEEDED) Shared library: [libstdc++.so.6]
0x0000000000000001 (NEEDED) Shared library: [libm.so.6]
0x0000000000000001 (NEEDED) Shared library: [libgcc_s.so.1]
0x0000000000000001 (NEEDED) Shared library: [libc.so.6]
0x000000000000000c (INIT) 0x400500
0x000000000000000d (FINI) 0x4006f4
0x0000000000000019 (INIT_ARRAY) 0x600dc0
0x000000000000001b (INIT_ARRAYSZ) 8 (bytes)
0x000000000000001a (FINI_ARRAY) 0x600dc8
0x000000000000001c (FINI_ARRAYSZ) 8 (bytes)
0x000000006ffffef5 (GNU_HASH) 0x400298
0x0000000000000005 (STRTAB) 0x4003c0
0x0000000000000006 (SYMTAB) 0x4002d0
0x000000000000000a (STRSZ) 171 (bytes)
0x000000000000000b (SYMENT) 24 (bytes)
0x0000000000000015 (DEBUG) 0x0
0x0000000000000003 (PLTGOT) 0x601000
0x0000000000000002 (PLTRELSZ) 72 (bytes)
0x0000000000000014 (PLTREL) RELA
0x0000000000000017 (JMPREL) 0x4004b8
0x0000000000000007 (RELA) 0x4004a0
0x0000000000000008 (RELASZ) 24 (bytes)
0x0000000000000009 (RELAENT) 24 (bytes)
0x000000006ffffffe (VERNEED) 0x400480
0x000000006fffffff (VERNEEDNUM) 1
0x000000006ffffff0 (VERSYM) 0x40046c
0x0000000000000000 (NULL) 0x0
g++ --std=c++11 -Ifooapi -Ibarapi main.cpp -o main -Llib -lbar -lfoo
ldd main
linux-vdso.so.1 => (0x00007ffc4efc7000)
libbar.so.1.0.0 => not found
libfoo.so.1.0.0 => not found
libstdc++.so.6 => /lib64/libstdc++.so.6 (0x00007fb8a221f000)
libm.so.6 => /lib64/libm.so.6 (0x00007fb8a1f1d000)
libgcc_s.so.1 => /lib64/libgcc_s.so.1 (0x00007fb8a1d07000)
libc.so.6 => /lib64/libc.so.6 (0x00007fb8a193a000)
/lib64/ld-linux-x86-64.so.2 (0x00007fb8a2526000)
LD_LIBRARY_PATH=lib ./main
foo doimpl 10 version 1 foo
foo doimpl 20 version 1 foo
bar doimpl 20 version 1 bar
Upgrade libfoo
cd lib; rm libfoo.so.1; rm libfoo.so; ln -s libfoo.so.1.0.2 libfoo.so.1; ln -s libfoo.so.1 libfoo.so; cd ..
total 60
lrwxrwxrwx. 1 amd amd 11 Sep 4 11:37 libbar.so -> libbar.so.1
lrwxrwxrwx. 1 amd amd 15 Sep 4 11:37 libbar.so.1 -> libbar.so.1.0.0
-rwxrwxr-x. 1 amd amd 20160 Sep 4 11:47 libbar.so.1.0.0
lrwxrwxrwx. 1 amd amd 11 Sep 4 13:06 libfoo.so -> libfoo.so.1
lrwxrwxrwx. 1 amd amd 15 Sep 4 13:06 libfoo.so.1 -> libfoo.so.1.0.2
-rwxrwxr-x. 1 amd amd 20120 Sep 4 11:16 libfoo.so.1.0.0
-rwxrwxr-x. 1 amd amd 20120 Sep 4 11:23 libfoo.so.1.0.2
LD_LIBRARY_PATH=lib ./main
foo doimpl 10 version 1 foo
foo doimpl 20 version 1 foo
bar doimpl 20 version 1 bar
main app works as libfoo.so.1.0.0 - old version still exists
mv lib/libfoo.so.1.0.0 lib/hide_libfoo.so.1.0.0
total 60
-rwxrwxr-x. 1 amd amd 20120 Sep 4 11:16 hide_libfoo.so.1.0.0
lrwxrwxrwx. 1 amd amd 11 Sep 4 11:37 libbar.so -> libbar.so.1
lrwxrwxrwx. 1 amd amd 15 Sep 4 11:37 libbar.so.1 -> libbar.so.1.0.0
-rwxrwxr-x. 1 amd amd 20160 Sep 4 11:47 libbar.so.1.0.0
lrwxrwxrwx. 1 amd amd 11 Sep 4 13:06 libfoo.so -> libfoo.so.1
lrwxrwxrwx. 1 amd amd 15 Sep 4 13:06 libfoo.so.1 -> libfoo.so.1.0.2
-rwxrwxr-x. 1 amd amd 20120 Sep 4 11:23 libfoo.so.1.0.2
LD_LIBRARY_PATH=lib ./main
./main: error while loading shared libraries: libfoo.so.1.0.0: cannot open shared object file: No such file or directory
Recompile libbar to use upgraded libfoo
readelf -d lib/libbar.so | head -15
Dynamic section at offset 0x2d98 contains 30 entries:
Tag Type Name/Value
0x0000000000000001 (NEEDED) Shared library: [libfoo.so.1.0.0]
0x0000000000000001 (NEEDED) Shared library: [libstdc++.so.6]
0x0000000000000001 (NEEDED) Shared library: [libm.so.6]
0x0000000000000001 (NEEDED) Shared library: [libgcc_s.so.1]
0x0000000000000001 (NEEDED) Shared library: [libc.so.6]
0x000000000000000e (SONAME) Library soname: [libbar.so.1.0.0]
0x000000000000000f (RPATH) Library rpath: [$ORIGIN]
0x000000000000000c (INIT) 0x1560
0x000000000000000d (FINI) 0x2010
0x0000000000000019 (INIT_ARRAY) 0x202d68
0x000000000000001b (INIT_ARRAYSZ) 16 (bytes)
0x000000000000001a (FINI_ARRAY) 0x202d78
g++ -fPIC -fvisibility=hidden -shared -Wl,-soname,libbar.so.1.0.1 -Wl,-rpath,$ORIGIN -o lib/libbar.so.1.0.1 barapi/bar.o -Llib -lfoo
total 80
-rwxrwxr-x. 1 amd amd 20120 Sep 4 11:16 hide_libfoo.so.1.0.0
lrwxrwxrwx. 1 amd amd 11 Sep 4 11:37 libbar.so -> libbar.so.1
lrwxrwxrwx. 1 amd amd 15 Sep 4 11:37 libbar.so.1 -> libbar.so.1.0.0
-rwxrwxr-x. 1 amd amd 20160 Sep 4 11:47 libbar.so.1.0.0
-rwxrwxr-x. 1 amd amd 20160 Sep 4 13:15 libbar.so.1.0.1
lrwxrwxrwx. 1 amd amd 11 Sep 4 13:06 libfoo.so -> libfoo.so.1
lrwxrwxrwx. 1 amd amd 15 Sep 4 13:06 libfoo.so.1 -> libfoo.so.1.0.2
-rwxrwxr-x. 1 amd amd 20120 Sep 4 11:23 libfoo.so.1.0.2
libbar.so.1.0.1 is new
./main: error while loading shared libraries: libfoo.so.1.0.0: cannot open shared object file: No such file or directory
readelf -d main | head -10
Dynamic section at offset 0xdd8 contains 29 entries:
Tag Type Name/Value
0x0000000000000001 (NEEDED) Shared library: [libbar.so.1.0.0]
0x0000000000000001 (NEEDED) Shared library: [libfoo.so.1.0.0]
0x0000000000000001 (NEEDED) Shared library: [libstdc++.so.6]
0x0000000000000001 (NEEDED) Shared library: [libm.so.6]
0x0000000000000001 (NEEDED) Shared library: [libgcc_s.so.1]
0x0000000000000001 (NEEDED) Shared library: [libc.so.6]
0x000000000000000c (INIT) 0x400500
main app still linked with old libbar, fails
readelf -d lib/libbar.so.1.0.1 | head -10
Dynamic section at offset 0x2d98 contains 30 entries:
Tag Type Name/Value
0x0000000000000001 (NEEDED) Shared library: [libfoo.so.1.0.2]
0x0000000000000001 (NEEDED) Shared library: [libstdc++.so.6]
0x0000000000000001 (NEEDED) Shared library: [libm.so.6]
0x0000000000000001 (NEEDED) Shared library: [libgcc_s.so.1]
0x0000000000000001 (NEEDED) Shared library: [libc.so.6]
0x000000000000000e (SONAME) Library soname: [libbar.so.1.0.1]
0x000000000000000f (RPATH) Library rpath: [$ORIGIN]
new libbar.so.1.0.1 needs libfoo.so.1.0.2
rebuild main app
g++ --std=c++11 -Ifooapi -Ibarapi main.cpp -o main -Llib -lbar -lfoo
/usr/bin/ld: warning: libfoo.so.1.0.0, needed by lib/libbar.so, not found (try using -rpath or -rpath-link)
Update libbar so links
cd lib; rm libbar.so.1; rm libbar.so; ln -s libbar.so.1.0.1 libbar.so.1; ln -s libbar.so.1 libbar.so; cd ..
total 80
-rwxrwxr-x. 1 amd amd 20120 Sep 4 11:16 hide_libfoo.so.1.0.0
lrwxrwxrwx. 1 amd amd 11 Sep 4 13:20 libbar.so -> libbar.so.1
lrwxrwxrwx. 1 amd amd 15 Sep 4 13:20 libbar.so.1 -> libbar.so.1.0.1
-rwxrwxr-x. 1 amd amd 20160 Sep 4 11:47 libbar.so.1.0.0
-rwxrwxr-x. 1 amd amd 20160 Sep 4 13:15 libbar.so.1.0.1
lrwxrwxrwx. 1 amd amd 11 Sep 4 13:06 libfoo.so -> libfoo.so.1
lrwxrwxrwx. 1 amd amd 15 Sep 4 13:06 libfoo.so.1 -> libfoo.so.1.0.2
-rwxrwxr-x. 1 amd amd 20120 Sep 4 11:23 libfoo.so.1.0.2
libbar.so points to the latest, libfoo.so points to what libbar needs
rebuild main app
g++ --std=c++11 -Ifooapi -Ibarapi main.cpp -o main -Llib -lbar -lfoo
It worked
ldd main
linux-vdso.so.1 => (0x00007ffc04bfb000)
libbar.so.1.0.1 => not found
libfoo.so.1.0.2 => not found
libstdc++.so.6 => /lib64/libstdc++.so.6 (0x00007f7803266000)
libm.so.6 => /lib64/libm.so.6 (0x00007f7802f64000)
libgcc_s.so.1 => /lib64/libgcc_s.so.1 (0x00007f7802d4e000)
libc.so.6 => /lib64/libc.so.6 (0x00007f7802981000)
/lib64/ld-linux-x86-64.so.2 (0x00007f780356d000)
LD_LIBRARY_PATH=lib ldd main
linux-vdso.so.1 => (0x00007ffe838c8000)
libbar.so.1.0.1 => lib/libbar.so.1.0.1 (0x00007f9141780000)
libfoo.so.1.0.2 => lib/libfoo.so.1.0.2 (0x00007f914157c000)
libstdc++.so.6 => /lib64/libstdc++.so.6 (0x00007f9141275000)
libm.so.6 => /lib64/libm.so.6 (0x00007f9140f73000)
libgcc_s.so.1 => /lib64/libgcc_s.so.1 (0x00007f9140d5d000)
libc.so.6 => /lib64/libc.so.6 (0x00007f9140990000)
/lib64/ld-linux-x86-64.so.2 (0x00007f9141984000)
Shows main using correct versions of libs
LD_LIBRARY_PATH=lib ./main
foo 2 doimpl 10 version 2 foo
foo 2 doimpl 20 version 2 foo
bar doimpl 20 version 1 bar
Note libfoo version 2 got called by bar
How to make updates to foo so libbar doesn't need to be recompiled
use correct soname spec
build libfoo
change just libfile names
g++ -fPIC -fvisibility=hidden -shared -Wl,-soname,libfoo.so.1 -o lib.so/libfoo.so.1.0.0 fooapi/foo.o
cd lib.so; ln -s libfoo.so.1.0.0 libfoo.so.1; ln -s libfoo.so.1 libfoo.so; cd ..
g++ -fPIC -fvisibility=hidden -shared -Wl,-soname,libbar.so.1 -Wl,-rpath,$ORIGIN -o lib.so/libbar.so.1.0.0 barapi/bar.o -Llib.so -lfoo
ldd lib.so/libbar.so.1.0.0
linux-vdso.so.1 => (0x00007ffc2a17c000)
libfoo.so.1 => /datadisk/git-repos/sharedlib/lib.so/libfoo.so.1 (0x00007f46b803e000)
libstdc++.so.6 => /lib64/libstdc++.so.6 (0x00007f46b7d37000)
libm.so.6 => /lib64/libm.so.6 (0x00007f46b7a35000)
libgcc_s.so.1 => /lib64/libgcc_s.so.1 (0x00007f46b781f000)
libc.so.6 => /lib64/libc.so.6 (0x00007f46b7452000)
/lib64/ld-linux-x86-64.so.2 (0x00007f46b8446000)
Note libbar only depends on libfoo.so.1 not libfoo.so.1.0.0, last 2 digits dont care
Build main
/usr/bin/ld: cannot find -lbar
collect2: error: ld returned 1 exit status
cd lib.so; ln -s libbar.so.1.0.0 libbar.so.1; ln -s libbar.so.1 libbar.so; cd ..
g++ --std=c++11 -Ifooapi -Ibarapi main.cpp -o main -Llib.so -lbar -lfoo
ldd main
linux-vdso.so.1 => (0x00007ffec730a000)
libbar.so.1 => not found
libfoo.so.1 => not found
libstdc++.so.6 => /lib64/libstdc++.so.6 (0x00007f2547558000)
libm.so.6 => /lib64/libm.so.6 (0x00007f2547256000)
libgcc_s.so.1 => /lib64/libgcc_s.so.1 (0x00007f2547040000)
libc.so.6 => /lib64/libc.so.6 (0x00007f2546c73000)
/lib64/ld-linux-x86-64.so.2 (0x00007f254785f000)
note the lib versions conform to soname spec
LD_LIBRARY_PATH=lib.so ./main
foo doimpl 10 version 1 foo
foo doimpl 20 version 1 foo
bar doimpl 20 version 1 bar
Now update libfoo
g++ -fPIC -fvisibility=hidden -shared -Wl,-soname,libfoo.so.1 -o lib.so/libfoo.so.1.0.2 fooapir2/foo.o
keep soname_spec compatible but filename changed
ls -l lib.so
total 60
lrwxrwxrwx. 1 amd amd 11 Sep 4 13:34 libbar.so -> libbar.so.1
lrwxrwxrwx. 1 amd amd 15 Sep 4 13:34 libbar.so.1 -> libbar.so.1.0.0
-rwxrwxr-x. 1 amd amd 20160 Sep 4 13:31 libbar.so.1.0.0
lrwxrwxrwx. 1 amd amd 11 Sep 4 13:30 libfoo.so -> libfoo.so.1
lrwxrwxrwx. 1 amd amd 15 Sep 4 13:30 libfoo.so.1 -> libfoo.so.1.0.0
-rwxrwxr-x. 1 amd amd 20120 Sep 4 13:29 libfoo.so.1.0.0
-rwxrwxr-x. 1 amd amd 20120 Sep 4 13:37 libfoo.so.1.0.2
rerun main
foo doimpl 10 version 1 foo
foo doimpl 20 version 1 foo
bar doimpl 20 version 1 bar
it worked but did not use updated libfoo version 2
update libfoo.so.1 soname link to point to lated
cd lib.so; rm libfoo.so.1; ln -s libfoo.so.1.0.2 libfoo.so.1; cd ..
ls -l lib.so
total 60
lrwxrwxrwx. 1 amd amd 11 Sep 4 13:34 libbar.so -> libbar.so.1
lrwxrwxrwx. 1 amd amd 15 Sep 4 13:34 libbar.so.1 -> libbar.so.1.0.0
-rwxrwxr-x. 1 amd amd 20160 Sep 4 13:31 libbar.so.1.0.0
lrwxrwxrwx. 1 amd amd 11 Sep 4 13:30 libfoo.so -> libfoo.so.1
lrwxrwxrwx. 1 amd amd 15 Sep 4 13:39 libfoo.so.1 -> libfoo.so.1.0.2
-rwxrwxr-x. 1 amd amd 20120 Sep 4 13:29 libfoo.so.1.0.0
-rwxrwxr-x. 1 amd amd 20120 Sep 4 13:37 libfoo.so.1.0.2
rerun main - does it pick new libfoo
LD_LIBRARY_PATH=lib.so ./main
foo 2 doimpl 10 version 2 foo
foo 2 doimpl 20 version 2 foo
bar doimpl 20 version 1 bar
yes foo 2
no need to rebuild libbar or main with updated libfoo as it was compatible
