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sorush-r
Asked: 2012-09-29 01:39:04 +0800 CST

Strange problem with libc: undefined reference to `crypt'

  • 772

I moved from Archlinux to Kubuntu 12.04 yesterday.

I compiled buildroot 2012.08 on Archlinux without any problem. Though on Kubuntu libcrypt seems to be broken. sysvinit can't find it anywhere. glibc-dev and all dependencies are installed.

How do I link to libcrypt? Or, which package containts that library?

...
bc-gcc   sulogin.o    -o sulogin
sulogin.o: In function `main':
sulogin.c:(.text+0x49d): undefined reference to `crypt'
collect2: ld returned 1 exit status
compiling

3 Answers

  1. Try adding '-lcrypt' after any objects used in linking; I've had a couple of instances where gcc would complain about crypt if -lcrypt wasn't near the end of the link list.

    In other words, try something like:

    gcc -D FOO -D BAR -W -Wall -pedantic -O2 foo.o bar.o -lnsl -lcrypt -o baz

    as opposed to

    gcc -D FOO -D BAR -W -Wall -pedantic -O2 -lnsl -lcrypt foo.o baz.o -o baz
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  2. undefined reference to 'crypt' is a linker error.

    Try linking with -lcrypt : gcc ....-lcrypt

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  3. For those of you using super-auto-magical CMAKE like me, try to add

    target_link_libraries(your_binary_name PRIVATE libcrypt.so)

    to your CMakeLists.txt

    Alternatively, replace PRIVATE for PUBLIC as needed..

    If you have well established paths to libraries (e.g. all needed libs in /usr/lib), you may be fine with just stating in CMakeLists.txt:

    set(CMAKE_CXX_FLAGS "-lcrypt")

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