I'm trying to interpose system's open() function with my own using
the dyld, I had no problem with that on Tiger, but the same code on
Leopard doesn't work any longer. I compile my library this way:
gcc -arch ppc -dynamiclib -fno-common -o open_interposer.dylib
open_interposer.c
and then I run my app this way:
DYLD_INSERT_LIBRARIES=open_interposer.dylib
DYLD_FORCE_FLAT_NAMESPACE=1 ./my_app
and the application is still using system's open() function instead
of mine :(. DYLD_PRINT_LIBRARIES=1 shows that pen_interposer.dylib
is loaded before other libs.
open() is more than meets the eye in Leopard. You may need to
interpose more than one entry point.
When you type `open(...)` in your C code, one of those symbol names
is chosen depending on your compile options (specifically UNIX
compliance, in this case). You can use `nm -m` on your app to see
which version it's linking to. For example, a trivial 32-bit i386
test program built on Leopard with `cc` and no other options uses
_open$UNIX2003.
Good point. Be sure to include the appropriate header files so that
you get the $UNIX2003 magic. Relying on implicit function
declarations will not work.
(I don't know whether function interposing still works the way you
want even after working around this change.)
Yes, it will.
- Kevin
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