Fixing the gcc linker order

[jpereira]

Hi,

I got the below errors during the build.

# make
(cd src; make all)
make[1]: Entering directory '/home/jpereira/Devel/github-jpereira/lua-ffi-yara.git/src'
gcc -shared -o libyawrap.so yawrap.o -Wl,-Bstatic -lyara -Wl,-Bdynamic -lpthread -lcrypto
/usr/bin/ld: /usr/lib/gcc/x86_64-linux-gnu/6/../../../x86_64-linux-gnu/libyara.a(object.o): relocation R_X86_64_PC32 against symbol `stderr@@GLIBC_2.2.5' can not be used when making a shared object; recompile with -fPIC
/usr/bin/ld: final link failed: Bad value
collect2: error: ld returned 1 exit status
Makefile:19: recipe for target 'libyawrap' failed
make[1]: *** [libyawrap] Error 1
make[1]: Leaving directory '/home/jpereira/Devel/github-jpereira/lua-ffi-yara.git/src'
Makefile:2: recipe for target 'all' failed
make: *** [all] Error 2
#

My setup is:

# lsb_release -a
No LSB modules are available.
Distributor ID:	Ubuntu
Description:	Ubuntu 16.10
Release:	16.10
Codename:	yakkety
# dpkg -s gcc | grep Version
Version: 4:6.1.1-1ubuntu2
#

you can see the fix into this PR.

[robert-zenedge]

Looks like your libyara needs to be rebuilt with --with-pic, based on the output of ld:

/usr/bin/ld: /usr/lib/gcc/x86_64-linux-gnu/6/../../../x86_64-linux-gnu/libyara.a(object.o): relocation R_X86_64_PC32 against symbol `stderr@@GLIBC_2.2.5' can not be used when making a shared object; recompile with -fPIC

[jpereira]

But, if the problem is the -fPIC, the linker order shouldn't work. do you agree?

[robert-zenedge]

I'm not exactly sure how changing the linker order here affects things, but there are a few effects that seem undesirable. As a test, I installed the system libyara-dev package and built with your diff. The resulting ldd:

[poprocks@soter]─[~/code/C/yara] $ ldd ./libyawrap.so 
	linux-vdso.so.1 =>  (0x00007fff92faf000)
	libc.so.6 => /lib/x86_64-linux-gnu/libc.so.6 (0x00007fe09a248000)
	/lib64/ld-linux-x86-64.so.2 (0x00007fe09a831000)

So we're not linked to pthread or crypto libs, yet those libs are not statically compiled in, so we would run into runtime issues here. Also, older versions of yara had struct element name changes, so yara lib version 3.5 is a requirement. I'll add that note to the Readme as well.