[TEMP. FIX] undefined reference to `pthread_atfork'

[concatime]

Hi. I'm trying to build Nginx with this script, but I get this error.

objs/addon/src/ngx_http_brotli_filter_module.o \
objs/ngx_modules.o \
-ldl -lpthread -lpthread -lcrypt -lm ../pcre-8.41/.libs/libpcre.a ../openssl/.openssl/lib/libssl.a ../openssl/.openssl/lib/libcrypto.a -ldl ../libatomic_ops-7.6.0/src/libatomic_ops.a \
-Wl,-E
../openssl/.openssl/lib/libcrypto.a(threads_pthread.o): In function `openssl_init_fork_handlers':
threads_pthread.c:(.text+0x1ba): undefined reference to `pthread_atfork'
collect2: error: ld returned 1 exit status
make[1]: *** [objs/Makefile:309: objs/nginx] Error 1

I was able to build two weeks ago, so this issue must be new.

[EDIT] See the temporary fix.

[richsalz]

What platform? Pthread_atfork is a standard API in pthreads library.

[concatime]

Well, I tried on my server, which is Debian 9 from OVH, and on my desktop, OpenSUSE Tumbleweed. Both with the same result. I used gcc-7/g++-7, maybe because of this?

[concatime]

Well, this error happens also with gcc/g++ 6.

[richsalz]

It’s the pthreads library.

[t-j-h]

Note: pthread_atfork can be in libc rather than libpthreads.

[richsalz]

Yes, good point. Either way, is it reasonable for us to assume that pthread_atfork exists if posix threads is used on Linux? Or do we need another Compile flag?

[levitte]

It looks to me like this is an order problem:

objs/addon/src/ngx_http_brotli_filter_module.o \
objs/ngx_modules.o \
-ldl -lpthread -lpthread -lcrypt -lm ../pcre-8.41/.libs/libpcre.a ../openssl/.openssl/lib/libssl.a ../openssl/.openssl/lib/libcrypto.a -ldl ../libatomic_ops-7.6.0/src/libatomic_ops.a \
-Wl,-E

Shouldn't -lpthread appear last to make sure the symbol references in libcrypto.a get properly resolved?

[kroeckx]

You should use "-pthread", not "-lpthread".

…

-lpthread will probably also work if you move it to the end of the libraries. For some reason you're also using a static version of all the libraries. I suggest you use shared versions instead if you can. Your OS should already provide shared versions of those libraries.

[paulidale]

I'm with @levitte the -lpthread should be later in the command line. After the .a files.
You shouldn't need it twice. -ldl is there twice too.

That is more like:

objs/addon/src/ngx_http_brotli_filter_module.o \
objs/ngx_modules.o \
 ../pcre-8.41/.libs/libpcre.a ../openssl/.openssl/lib/libssl.a ../openssl/.openssl/lib/libcrypto.a ../libatomic_ops-7.6.0/src/libatomic_ops.a \
-ldl -lpthread -lpthread -lcrypt -lm -Wl,-E

[concatime]

So finally, It seems that the Nginx configuration file is quite odd. So the the temporary solution for now is a hack. After running the ./configure, in obj/Makefile, you should remove the first -lpthread and move the second to the end of the line, right before \. Since the github repo. of Nginx is just a mirror, I can't submit an issue about this.

Thanks to all of you who supported me through this whole issue.

[concatime]

We should leave this post open until Nginx patches this.

Ok, cool.

[richsalz]

We're glad you got it working. You can still open an issue with nginx. OpenSSL's GH repo is just a downstream clone and we take issues :) This will come up for anyone who is building from master and the next release. Their config file was wrong and they just got lucky until now.

[t0mtaylor]

this worked for me:

	-L ../openssl-dev/.openssl/lib/ -ldl -lcrypt -lm ../pcre-8.39/.libs/libpcre.a ../openssl-dev/.openssl/lib/libssl.a ../openssl-dev/.openssl/lib/libcrypto.a -ldl ../zlib-1.2.8/libz.a -lpthread \
	-Wl,-E

[levitte]

Hmm, there was another issue where someone complained that our libcrypto.pc didn't have the necessary options to have the pthread library be part of the final link. Does nginx us pkgconfig files to figure out compile and link options? Then that might be the issue, and that falls back on us.

[meilihao]

Today i get the same problem when use --with-openssl=../openssl-master --with-openssl-opt='enable-tls1_3':

../openssl-master/.openssl/lib/libcrypto.a(threads_pthread.o)：In function ‘fork_once_func’：
threads_pthread.c:(.text+0x16)：undefined reference to `pthread_atfork'

openssl : d2ef6e4
OS: CentOS Linux release 7.4.1708 (Core)
nginx: nginx-1.13.5
gcc : gcc (GCC) 4.8.5 20150623 (Red Hat 4.8.5-16)

[meilihao]

And i add -pthread to --with-cc-opt to build again, but get a same error:

...
-Wl,-z,relro -Wl,-z,now -pie -ldl -lpthread -lcrypt -lpcre ../openssl-master/.openssl/lib/libssl.a ../openssl-master/.openssl/lib/libcrypto.a -ldl -lz \
-Wl,-E
../openssl-master/.openssl/lib/libcrypto.a(threads_pthread.o)：In function ‘fork_once_func’：
threads_pthread.c:(.text+0x16)：undefined reference to 'pthread_atfork'

[meilihao]

I solved this by concatime's solution

[levitte]

Yeah, it's a solution, but kind of a hack. If we're at fault, I will gladly resolve it, but maybe not this week (out travelling)

[dsamarin]

For those who want a scripted temporary solution:

gawk -i inplace \
  '/pthread/ { sub(/-lpthread /, ""); sub(/-lpthread /, ""); sub(/\\/, "-lpthread \\"); print } ! /pthread/ { print }' \
  "objs/Makefile"

[mattcaswell]

@levitte - do we need to do something here?

[levitte]

Yes, we do, we need to make sure that -pthread is part of ex_libs in config targets where this is present in cflags. That way, it will end up in Libs.private in libcrypto.pc

[levitte]

Fixes in #5134 (master) and #5135 (1.1.0)

[khs1994]

nginx 1.13.11 fix

• nginx/nginx@90ca107

[r3k2]

Hello Im having this same issue under

Ubuntu 18.04.3 LTS

with:

  8%] Linking CXX executable test_cypher_suites
/usr/lib/x86_64-linux-gnu/libcrypto.a(threads_pthread.o): In function `fork_once_func':
(.text+0x16): undefined reference to `pthread_atfork'
clang: error: linker command failed with exit code 1 (use -v to see invocation)
libraries/fc/test/crypto/CMakeFiles/test_cypher_suites.dir/build.make:113: recipe for target 'libraries/fc/test/crypto/test_cypher_suites' failed
make[2]: *** [libraries/fc/test/crypto/test_cypher_suites] Error 1
CMakeFiles/Makefile2:789: recipe for target 'libraries/fc/test/crypto/CMakeFiles/test_cypher_suites.dir/all' failed
make[1]: *** [libraries/fc/test/crypto/CMakeFiles/test_cypher_suites.dir/all] Error 2
Makefile:162: recipe for target 'all' failed
make: *** [all] Error 2

none of the work around did work for me, because I can't downgrade to that version with apt

[levitte]

You should look into the order in which the linking command line gets the different libraries, which means you need to tell your make to be a bit more verbose

[SergeyJames]

In my case, building of openssl library with flag no-threads, was the solution:

./config  no-threads

[ccy234]

And i add -pthread to --with-cc-opt to build again, but get a same error:

...
-Wl,-z,relro -Wl,-z,now -pie -ldl -lpthread -lcrypt -lpcre ../openssl-master/.openssl/lib/libssl.a ../openssl-master/.openssl/lib/libcrypto.a -ldl -lz \
-Wl,-E
../openssl-master/.openssl/lib/libcrypto.a(threads_pthread.o)：In function ‘fork_once_func’：
threads_pthread.c:(.text+0x16)：undefined reference to 'pthread_atfork'

you should use "--with-ld-opt=-pthread"