Make file Linking issue Undefined symbols for architecture x86_64 - c++

Question

I am working on getting a few files to link together using my make file and c++ and am getting the following error when running make.
g++ -bind_at_load `pkg-config --cflags opencv` -c -o compute_gist.o compute_gist.cpp
g++ -bind_at_load `pkg-config --cflags opencv` -c -o gist.o gist.cpp
g++ -bind_at_load `pkg-config --cflags opencv` -c -o standalone_image.o standalone_image.cpp
g++ -bind_at_load `pkg-config --cflags opencv` -c -o IplImageConverter.o IplImageConverter.cpp
g++ -bind_at_load `pkg-config --cflags opencv` -c -o GistCalculator.o GistCalculator.cpp
g++ -bind_at_load `pkg-config --cflags opencv` `pkg-config --libs opencv` compute_gist.o gist.o standalone_image.o IplImageConverter.o GistCalculator.o -o rungist
Undefined symbols for architecture x86_64:
"color_gist_scaletab(color_image_t*, int, int, int const*)", referenced from:
_main in compute_gist.o
ld: symbol(s) not found for architecture x86_64
collect2: ld returned 1 exit status
make: *** [rungist] Error 1
My makefile is as follows (Note, I don't need opencv bindings yet, but will be coding in opencv later.
CXX = g++
CXXFLAGS = -bind_at_load `pkg-config --cflags opencv`
LFLAGS = `pkg-config --libs opencv`
SRC = \
compute_gist.cpp \
gist.cpp \
standalone_image.cpp \
IplImageConverter.cpp \
GistCalculator.cpp
OBJS = $(SRC:.cpp=.o)
rungist: $(OBJS)
$(CXX) $(CXXFLAGS) $(LFLAGS) $(OBJS) -o $#
all: rungist
clean:
rm -rf $(OBJS) rungist
The method header is located in gist.h
float *color_gist_scaletab(color_image_t *src, int nblocks, int n_scale, const int *n_orientations);
And the method is defined in gist.cpp
float *color_gist_scaletab(color_image_t *src, int w, int n_scale, const int *n_orientation) {
And finally the compute_gist.cpp (main file)
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include "gist.h"
static color_image_t *load_ppm(const char *fname) {
FILE *f=fopen(fname,"r");
if(!f) {
perror("could not open infile");
exit(1);
}
int width,height,maxval;
if(fscanf(f,"P6 %d %d %d",&width,&height,&maxval)!=3 || maxval!=255) {
fprintf(stderr,"Error: input not a raw PPM with maxval 255\n");
exit(1);
}
fgetc(f); /* eat the newline */
color_image_t *im=color_image_new(width,height);
int i;
for(i=0;i<width*height;i++) {
im->c1[i]=fgetc(f);
im->c2[i]=fgetc(f);
im->c3[i]=fgetc(f);
}
fclose(f);
return im;
}
static void usage(void) {
fprintf(stderr,"compute_gist options... [infilename]\n"
"infile is a PPM raw file\n"
"options:\n"
"[-nblocks nb] use a grid of nb*nb cells (default 4)\n"
"[-orientationsPerScale o_1,..,o_n] use n scales and compute o_i orientations for scale i\n"
);
exit(1);
}
int main(int argc,char **args) {
const char *infilename="/dev/stdin";
int nblocks=4;
int n_scale=3;
int orientations_per_scale[50]={8,8,4};
while(*++args) {
const char *a=*args;
if(!strcmp(a,"-h")) usage();
else if(!strcmp(a,"-nblocks")) {
if(!sscanf(*++args,"%d",&nblocks)) {
fprintf(stderr,"could not parse %s argument",a);
usage();
}
} else if(!strcmp(a,"-orientationsPerScale")) {
char *c;
n_scale=0;
for(c=strtok(*++args,",");c;c=strtok(NULL,",")) {
if(!sscanf(c,"%d",&orientations_per_scale[n_scale++])) {
fprintf(stderr,"could not parse %s argument",a);
usage();
}
}
} else {
infilename=a;
}
}
color_image_t *im=load_ppm(infilename);
//Here's the method call -> :(
float *desc=color_gist_scaletab(im,nblocks,n_scale,orientations_per_scale);
int i;
int descsize=0;
//compute descriptor size
for(i=0;i<n_scale;i++)
descsize+=nblocks*nblocks*orientations_per_scale[i];
descsize*=3; // color
//print descriptor
for(i=0;i<descsize;i++)
printf("%.4f ",desc[i]);
printf("\n");
free(desc);
color_image_delete(im);
return 0;
}
Any help would be greatly appreciated. I hope this is enough info. Let me know if I need to add more.

Answer 1

I suspect that color_gist_scaletab should be declared as extern "C" in your header file:
extern "C" {
float *color_gist_scaletab(color_image_t *src, int nblocks, int n_scale, const int *n_orientations);
}

Answer 2

Your link command line is incorrect. See this answer.
However, that is likely not the problem you are seeing here.
What do the following commands print?
file gist.o
nm gist.o | grep color_gist_scaletab
I also see this very similar question. But there, color_gist_scaletab comes from gist.c, not gist.cpp. You didn't just rename gist.c to gist.cpp, did you? Don't do that.