How to set the runtime path (-rpath) of an executable with gcc under Mac OSX?

I want to set under Mac OSX the runtime path of an executable (for the linker) at compile time, such that shared libraries at non-standard locations are found by the dynamic linker at program start.

Under Linux this is possible with -Xlinker -rpath -Xlinker /path/to (or using -Wl,-rpath,/path/to) and under Solaris you can add -R/path/to to the compiler command line.

I found some information that Mac OS X gcc has -rpath support since 10.5, i.e. since ~ 2008.

I tried to get it working with a minimal example - without success:

$ cat blah.c 
int blah(int b)
{
  return b+1;
}

And:

$ cat main.c 

#include <stdio.h>

int blah(int);

int main ()
{
  printf("%d\n", blah(22));
  return 0;
}

Compiled it like this:

$ gcc -c  blah.c
$ gcc -dynamiclib blah.o -o libblah.dylib
$ gcc main.c -lblah -L`pwd`  -Xlinker -rpath -Xlinker `pwd`/t

Now the test:

$ mkdir t
$ mv libblah.dylib t
$ ./a.out
dyld: Library not loaded: li开发者_JAVA百科bblah.dylib
  Referenced from: /Users/max/test/./a.out
  Reason: image not found
Trace/BPT trap

Thus the question: How to I set the runtime path for the linker under Mac OSX?

Btw, setting DYLD_LIBRARY_PATH works - but I don't want to use this hack.

Edit: Regarding otool -L:

$ otool -L a.out 
a.out:
        libblah.dylib (compatibility version 0.0.0, current version 0.0.0)
        /usr/lib/libSystem.B.dylib (compatibility version 1.0.0, current version 125.2.1)

It seems that otool -L only prints the library names (and probable the locations at link time) the executable was linked against and no runtime path information.

Found by experimentation, and inspecting the command lines generated by Xcode for a reference rpath demo project by Dave Driblin:

otool -L shows you the install name of the linked libraries. To get @rpath to work, you need to change the install name of the library:

$ gcc -dynamiclib blah.o -install_name @rpath/t/libblah.dylib -o libblah.dylib
$ mkdir t ; mv libblah.dylib t/
$ gcc main.c -lblah -L`pwd`/t -Xlinker -rpath -Xlinker `pwd`