After following the instructions in http://github.com/vlm/asn1c/blob/master/INSTALL
I do the following, in a new directory (i.e., Mac OS X folder):
# Terminal command line from: https://developer.apple.com/library/ios/releasenotes/General/ValidateAppStoreReceipt/Chapters/ValidateLocally.html#//apple_ref/doc/uid/TP40010573-CH1-SW3
asn1c -fnative-types receipt.ans1
# the file receipt.ans1 has contents from Listing 1-1 in the above URL
# converter-sample.c has a main. Don't want that!
rm converter-sample.c
rm Makefile.am.sample
Then, make sure to drag the resulting .c and .h files into an Xcode group, don't put the Mac folder directly into the project,or otherwise, the .c and .h files will not be added to the project. Thus, they won't build and you'll get linker errors