How do I link PCL library properly for use within an objective-C app compiled in Xcode?

Question

Question: How do I use PCL in the context of an Objective-C Cocoa (OSX, not iOS) app?

Tearing my hair out over this one.I can't get libpcl to link properly with my Objective C project in Xcode. I have checked and re-checked everything I can possibly think of. Probably doing something dumb, but I'm stumped.

Actual error is linker:

Undefined symbols for architecture x86_64:
"pcl::PassThrough<pcl::PointXYZ>::applyFilterIndices(std::__1::vector<int, std::__1::allocator<int> >&)", referenced from:
 pcl::PassThrough<pcl::PointXYZ>::applyFilter(std::__1::vector<int, std::__1::allocator<int> >&) in PCLProcess.o
 ld: symbol(s) not found for architecture x86_64

• The code I'm trying to compile is the standard tutorial code available here: http://pointclouds.org/documentation/tutorials/passthrough.php#passthrough

• I CAN get it to work without Xcode (using Cmake and command line compiling exactly as in the tutorial)

• I CAN create a "command line" project and compile and link a one-off CPP file using Xcode

• The issue is the same no matter what version of PCL I've tried. Macports, binary distro, self-compiled 1.6 and trunk. All the same result.

• I've tried several different machines, OSX 10.7 and 10.8, same issue on both.

• I've even run nm against the dylib to verify the missing symbols are in the library I'm linking (filters in this case)

Any thoughts much appreciated, I've lost half a week to this.

See this screenshot for a detailed error message.

Here is the code in question:

//PCLProcess.h
#import <Foundation/Foundation.h>
@interface PCLProcess : NSObject
@end

//PCLProcess.mm
#import "PCLProcess.h"
#include <pcl/point_types.h>
#include <pcl/filters/passthrough.h>

@implementation PCLProcess

-(void)tryThis{
   // Code cut and pasted from tutoral (see link above)
}

@end

Update

Here is one more clue. I am in over my head with respect to compilers/linkers and how they work, but now I think I know what is happening but not why (or how to fix it).

• I ran the linker tool manually, and out of desperation I started plugging in obsolete flags just to see what the results were. The previous error (above) identifies the missing symbols as ""pcl::PassThrough::applyFilterIndices(std::__1::vector >&)" but ld -y gave me this:

  ld: warning: option -y is obsolete and being ignored Undefined symbols for architecture x86_64:"__ZN3pcl11PassThroughINS_8PointXYZEE18applyFilterIndicesERNSt3__16vectorIiNS3_9allocatorIiEEEE", referenced from:__ZN3pcl11PassThroughINS_8PointXYZEE11applyFilterERNSt3__16vectorIiNS3_9allocatorIiEEEE in PCLProcess.o ld: symbol(s) not found for architecture x86_64

So then I went looking for that symbol and, sure enough, it's missing (or different):

nm /opt/local/lib/libpcl_filters.dylib | grep __ZN3pcl11PassThroughINS_8PointXYZEE18applyFilterIndices
00000000000a0fa0 
T  __ZN3pcl11PassThroughINS_8PointXYZEE18applyFilterIndicesERSt6vectorIiSaIiEE

I suspect name mangling? But again, I'm not really sure what I'm talking about at this point or (more importantly) how to fix it.

Answer 1

Short answer:

Two Build settings under "Build Options":

C++ Language Dialect: GNU++98[-std=gnu++98]

C++ Standard Library: libstdc++ (GNU C++ standard library)

This second setting (C++ Standard Library) is the crucial one; Using libc++ will produce the "undefined symbols" linker errors shown in the question above.

Details for anyone trying this:

This works with Xcode 4.62, llvm4.2, libpcl 1.7 (currently dev, I compiled from trunk) and boost 1.53. Along the way I ran into a known issue with Boost and Cocoa involving the use of nil (see this link:https://svn.boost.org/trac/boost/ticket/5010) and also some strangeness with boost traits (see this:c++: Boost 1.48 type traits and Cocoa inclusion weirdness) Consequently I ended up including PCL headers as follows:

#define nil Boost_nil
#define Nil Boost_Nil
#ifdef check
#undef check
#endif

#include <pcl/pcl_base.h>
#include <pcl/point_types.h>
#include <pcl/filters/passthrough.h>

#undef Nil
#undef nil