Clang error while creating shared library

Question

I want to compile a shared library on MBP and based on the advise given here, I have switched to clang (from gcc) to create the shared library. My makefile is:

CC = clang
CFLAGS = -c -fPIC -Wall -O3 -lpthread -g
BaseDir = /Users/admin/Prog/
Include = -I$(BaseDir)UMFPACK/Include -I$(BaseDir)AMD/Include -I$(BaseDir)SuiteSparse_config
Lib = -L$(BaseDir)UMFPACK/Lib -L$(BaseDir)AMD/Lib -L$(BaseDir)GotoBLAS2 -L$(BaseDir)SuiteSparse_config
AddFiles = -lumfpack -lamd -lgoto2 -lsuitesparseconfig
StaticLibs = $(BaseDir)GotoBLAS2/libgoto2.a $(BaseDir)UMFPACK/Lib/libumfpack.a $(BaseDir)AMD/Lib/libamd.a $(BaseDir)SuiteSparse_config/libsuitesparseconfig.a

all: TDS.o TDSJac.o ExtraRoutines.o CalcVFC.o TDS.h
        $(CC) $(Include) $(Lib) $(AddFiles) -dynamiclib -lpthread -o libTDS.so $^ -lm -g $(StaticLibs)

TDS.o: TDS.c TDS.h
        $(CC) $(Include) $(CFLAGS) $^

TDSJac.o: TDSJac.c TDS.h
        $(CC) $(CFLAGS) $^

ExtraRoutines.o: ExtraRoutines.c TDS.h
        $(CC) $(CFLAGS) $^

CalcVFC.o: CalcVFC.c TDS.h
        $(CC) $(CFLAGS) $^

MexFile: TDSGateway.c
        mex -g -largeArrayDims -ldl TDSGateway.c

Move:
        mv libTDS.so ../../
        mv TDSGateway.mexmaci64 ../../

What I do here is: 1) Only compile TDS.c, TDSJac.c, ExtraRoutines.c, and CalcVFC.c to create four corresponding object files. 2) Merging object files and creating a shared library using following command:

clang -I(Some folders) -L(Some folders) -l(Some libraries) -shared -lpthread -o libTDS.so TDS.o TDSJac.o ExtraRoutines.o CalcVFC.o TDS.h -lm -g
clang: error: cannot specify -o when generating multiple output files

As I am absolutely new to clang, I do not know what is wrong with Makefile. (If I replace CC=clang with CC=gcc, everything works good.) I searched the internet with no success. Manual page of clang says nothing about shared library. I could not even get anything out of clang homepage. It is appreciated if help me to work around this problem.

Thanks for your help in advance.

dhein · Accepted Answer · 2013-08-06 07:52:40Z

1

I had yesterday almost the same problem. But i never used cmake. I'm using an own makefile system of my company, so I just can tell you, what fixed the problem for me so far.

Clang has still some trouble with giving you the right hints on errorcase. The linking error was:

/usr/bin/ld: /usr/lib/crt1.o: relocation R_X86_64_32 against `_DYNAMIC' can not be used when making a shared object; recompile with -fPIC

I solved the problem as I figgered out, that the -shared Parameter has to be behind the -o X.o parameters. As I see this is not made in your case, too. You should try that first.

In our case I also had to parse the LFlags with -WL, or -L, (afaik it doesn't matter which one you take but I read about a clang bug in relation to -Wl,). But idk in how far you have to parse LFlags or not, when using cmake.

answered Aug 6, 2013 at 7:52

dhein

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cdunn2001 · Accepted Answer · 2015-05-28 17:55:39Z

1

You've listed headers (TDS.h) as dependencies, which is fine, but you've then used $^ as inputs, which includes all dependencies. You should not list a header as an input. It should not be on the command-line at all, and in clang this is actually an error.

The error message is obscure but easy to resolve. You have 2 choices:

Be explicit instead of using $^. You could use a variable for inputs and another for dependencies, e.g.; or
Use intermediate .o files instead of .c files as inputs to a .so. The *.o files can depend on any .h they include.

edited May 28, 2015 at 17:55

answered May 28, 2015 at 3:02

cdunn2001

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