Gcc, static library, external assembly becomes undefined

Question

I have a problem with g ++ creating an application that references a static library, where the latter should contain some global functions written in external asm files compiled with yasm. So in the library I have

#ifdef __cplusplus
extern "C" {
#endif

extern void __attribute__((cdecl)) interp1( char *pSrc );
extern void __attribute__((cdecl)) interp2( char *pSrc );

#ifdef __cplusplus
}
#endif

which I mention elsewhere in the library. Then the implementation is performed in the asm file, for example:

section .data
; (some data)
section .text
; (some text)

global _interp1
_interp1:
    ; (code ...)
    ret

global _interp2
_interp2:
    ; (code ...)
    ret

Compiling and linking works fine for the library, I do

yasm -f elf32 -O2 -o interp.o interp.asm

and then

ar -rc libInterp.a objs1.o [...] objsN.o interp.o 
ranlib libInterp.a

Now, finally, to link the library to the main application, I do

g++ -O4 -ffast-math -DNDEBUG -fomit-frame-pointer -DARCH_X86 -fPIC -o ../bin/interp this.o that.o -lboost_thread -lpthread ./libInterp.a 

and i get errors

undefined reference to `interp1'
undefined reference to `interp2'

What am I doing wrong here? any help is appreciated.

Answer 1

gcc . , .

, , .

, , , , , - :

• from http://svn.xiph.org/trunk/oggdsf/src/lib/codecs/webm/libvpx/src/vpx_ports/x86_abi_support.asm

  ; sym()
  ; Return the proper symbol name for the target ABI.
  ;
  ; Certain ABIs, notably MS COFF and Darwin MACH-O, require that symbols
  ; with C linkage be prefixed with an underscore.
  ;
  %ifidn   __OUTPUT_FORMAT__,elf32
  %define sym(x) x
  %elifidn __OUTPUT_FORMAT__,elf64
  %define sym(x) x
  %elifidn __OUTPUT_FORMAT__,x64
  %define sym(x) x
  %else
  %define sym(x) _ %+ x
  %endif
  

• from http://www.dcs.warwick.ac.uk/~peter/otherstuff.html

  %macro public_c_symbol 1
  GLOBAL %1,_%1
  %1:
  _%1:
  %endmacro
  
  public_c_symbol my_external_proc:
      ; ...
      RET