Undefined Symbols for Architecture i386: "_CRC32", referenced FROM:--CRC link error

Sometimes with other people's framework, you will encounter the following errors, is very scary, what things, I can not understand!!!

Undefined Symbols for Architecture i386:
"_release", referenced from:
-[demoannotationview Dealloc] in DEMOANNOTATIONVIEW.O
"_crc32", referenced from:
-[ziparchive Addfiletozip:newname:] in ZIPARCHIVE.O
_unzreadcurrentfile in UNZIP.O
_zipwriteinfileinzip in ZIP.O
"_deflate", referenced from:
_zipwriteinfileinzip in ZIP.O
_zipclosefileinzipraw in ZIP.O
"_deflateend", referenced from:
_zipclosefileinzipraw in ZIP.O
"_deflateinit2_", referenced from:
_ZIPOPENNEWFILEINZIP3 in ZIP.O
"_get_crc_table", referenced from:
_unzopencurrentfile3 in UNZIP.O
_ZIPOPENNEWFILEINZIP3 in ZIP.O
"_iconv", referenced from:
_qr_code_data_list_extract_text in Libzbar.a (QRDECTXT.O)
"_iconv_close", referenced from:
_qr_code_data_list_extract_text in Libzbar.a (QRDECTXT.O)
"_iconv_open", referenced from:
_qr_code_data_list_extract_text in Libzbar.a (QRDECTXT.O)
"_inflate", referenced from:
_unzreadcurrentfile in UNZIP.O
"_inflateend", referenced from:
_unzclosecurrentfile in UNZIP.O
"_inflateinit2_", referenced from:
_unzopencurrentfile3 in UNZIP.O
......

iOS compile sometimes this error, to note that the error is not undefined for architecture i386, but the following underscore the beginning of the variable is not defined, you need to import LIBZ to the project.

Build phases--> Link Binary with Libraries to import the libz.1.2.5.dylib.

Reminder: Next time you encounter CRC link error, please add libz.dylib to the project.

Undefined Symbols for Architecture i386: "_CRC32", referenced FROM:--CRC link error