Shared library broken on MinGW

[mmgen]

This stub compiles, links and runs on Linux

    #include <stdio.h>
    #include <secp256k1.h>
    
    int main()
    {
    	static secp256k1_context *ctx = NULL;
    	ctx = secp256k1_context_create(SECP256K1_CONTEXT_SIGN);
    	return 1;
    }

but produces the following linking error under MinGW:

    $ gcc my.c -lsecp256k1 -I/usr/local/include -L/usr/local/lib
    C:/msys/local/lib/libsecp256k1.a(libsecp256k1_la-secp256k1.o): In function `secp256k1_num_set_bin':
    c:\build\secp256k1/src/num_gmp_impl.h:49: undefined reference to `_imp____gmpn_set_str'
    C:/msys/local/lib/libsecp256k1.a(libsecp256k1_la-secp256k1.o): In function `secp256k1_num_mod_inverse':
    c:\build\secp256k1/src/num_gmp_impl.h:128: undefined reference to `_imp____gmpn_gcdext'
    C:/msys/local/lib/libsecp256k1.a(libsecp256k1_la-secp256k1.o): In function `secp256k1_num_get_bin':
    c:\build\secp256k1/src/num_gmp_impl.h:34: undefined reference to `_imp____gmpn_get_str'
    C:/msys/local/lib/libsecp256k1.a(libsecp256k1_la-secp256k1.o): In function `_gmpn_sub':
    c:/mingw/include/gmp.h:2097: undefined reference to `_imp____gmpn_sub_n'
    collect2.exe: error: ld returned 1 exit status

The undefined symbols:

    $ objdump.exe -t /usr/local/lib/libsecp256k1.a | grep imp_
    [116](sec  0)(fl 0x00)(ty   0)(scl   2) (nx 0) 0x00000000 __imp___iob
    [117](sec  0)(fl 0x00)(ty   0)(scl   2) (nx 0) 0x00000000 __imp____gmpn_set_str
    [118](sec  0)(fl 0x00)(ty   0)(scl   2) (nx 0) 0x00000000 __imp____gmpn_gcdext
    [119](sec  0)(fl 0x00)(ty   0)(scl   2) (nx 0) 0x00000000 __imp____gmpn_get_str
    [120](sec  0)(fl 0x00)(ty   0)(scl   2) (nx 0) 0x00000000 __imp____gmpn_sub_n

[sipa]

Does it work when you add -lgmp to the command line? I'm surprised it works in Linux without that.

[mmgen]

That did the trick! Thanks, Pieter! It does work in Linux without that, by the way.

[sipa]

Maybe you just compiled in linux without gmp dependency? (--without-bignum, or just no libgmp developer files available?)

[mmgen]

No extra options at all, just ./configure and make, and libgmp-dev is installed. But it compiles fine with just

    gcc my.c -lsecp256k1

[sipa]

Right, but your Linux build environment may just not have libgmp-dev, in which case configure will automatically build without libgmp support.

[mmgen]

I rebuilt and reinstalled the library; configure enables libgmp. Stub still compiles OK without -lgmp though. I think this is because Linux allows unresolved symbols in shared libraries.

    $ objdump -t /usr/local/lib/libsecp256k1.a | grep gmp
    0000000000000000         *UND*  0000000000000000 __gmpn_set_str
    0000000000000000         *UND*  0000000000000000 __gmpn_gcdext
    0000000000000000         *UND*  0000000000000000 __gmpn_get_str
    0000000000000000         *UND*  0000000000000000 __gmpn_sub_n

[thinkKundera]

@mmgen @sipa how to solve this in Mac OS X? thanks

[thinkKundera]

@mmgen @sipa and the using compiler is clang

[mmgen]

@Aparesse no idea, sorry