cmake error (can't resolve pthread_create?)

[ilya-ratner]

-- Found LLVM 3.8.0
-- Added 14 tests to 'ebpf-bcc' (0 xfails)
-- Added 14 tests to 'ebpf' (0 xfails)
-- Added 5 tests to 'p4' (0 xfails)
-- Added 533 tests to 'p4' (5 xfails)
-- Added 5 tests to 'err' (0 xfails)
-- Added 160 tests to 'err' (0 xfails)
-- Added 207 tests to 'p14_to_16' (0 xfails)
-- CTest parallel: -j 4
-- Configuring incomplete, errors occurred!
See also "/home/ilya/p4/p4c/build/CMakeFiles/CMakeOutput.log".
See also "/home/ilya/p4/p4c/build/CMakeFiles/CMakeError.log".

...Below is the dump of the CMakeError.log; it appears that it can't resolve pthread_create, even though I can link with it just fine, if I use '-lpthread'

cat /home/ilya/p4/p4c/build/CMakeFiles/CMakeError.log
Determining if the pthread_create exist failed with the following output:
Change Dir: /home/ilya/p4/p4c/build/CMakeFiles/CMakeTmp

Run Build Command:"/usr/bin/make" "cmTC_30d9b/fast"
/usr/bin/make -f CMakeFiles/cmTC_30d9b.dir/build.make CMakeFiles/cmTC_30d9b.dir/build
make[1]: Entering directory '/home/ilya/p4/p4c/build/CMakeFiles/CMakeTmp'
Building C object CMakeFiles/cmTC_30d9b.dir/CheckSymbolExists.c.o
/usr/bin/cc -o CMakeFiles/cmTC_30d9b.dir/CheckSymbolExists.c.o -c /home/ilya/p4/p4c/build/CMakeFiles/CMakeTmp/CheckSymbolExists.c
Linking C executable cmTC_30d9b
/usr/bin/cmake -E cmake_link_script CMakeFiles/cmTC_30d9b.dir/link.txt --verbose=1
/usr/bin/cc CMakeFiles/cmTC_30d9b.dir/CheckSymbolExists.c.o -o cmTC_30d9b -rdynamic
CMakeFiles/cmTC_30d9b.dir/CheckSymbolExists.c.o: In function main': CheckSymbolExists.c:(.text+0x16): undefined reference to pthread_create'
collect2: error: ld returned 1 exit status
CMakeFiles/cmTC_30d9b.dir/build.make:97: recipe for target 'cmTC_30d9b' failed
make[1]: *** [cmTC_30d9b] Error 1
make[1]: Leaving directory '/home/ilya/p4/p4c/build/CMakeFiles/CMakeTmp'
Makefile:126: recipe for target 'cmTC_30d9b/fast' failed
make: *** [cmTC_30d9b/fast] Error 2

File /home/ilya/p4/p4c/build/CMakeFiles/CMakeTmp/CheckSymbolExists.c:
/* */
#include <pthread.h>

int main(int argc, char** argv)
{
(void)argv;
#ifndef pthread_create
return ((int*)(&pthread_create))[argc];
#else
(void)argc;
return 0;
#endif
}

Determining if the function pthread_create exists in the pthreads failed with the following output:
Change Dir: /home/ilya/p4/p4c/build/CMakeFiles/CMakeTmp

Run Build Command:"/usr/bin/make" "cmTC_15b4a/fast"
/usr/bin/make -f CMakeFiles/cmTC_15b4a.dir/build.make CMakeFiles/cmTC_15b4a.dir/build
make[1]: Entering directory '/home/ilya/p4/p4c/build/CMakeFiles/CMakeTmp'
Building C object CMakeFiles/cmTC_15b4a.dir/CheckFunctionExists.c.o
/usr/bin/cc -DCHECK_FUNCTION_EXISTS=pthread_create -o CMakeFiles/cmTC_15b4a.dir/CheckFunctionExists.c.o -c /usr/share/cmake-3.5/Modules/CheckFunctionExists.c
Linking C executable cmTC_15b4a
/usr/bin/cmake -E cmake_link_script CMakeFiles/cmTC_15b4a.dir/link.txt --verbose=1
/usr/bin/cc -DCHECK_FUNCTION_EXISTS=pthread_create CMakeFiles/cmTC_15b4a.dir/CheckFunctionExists.c.o -o cmTC_15b4a -rdynamic -lpthreads
/usr/bin/ld: cannot find -lpthreads
collect2: error: ld returned 1 exit status
CMakeFiles/cmTC_15b4a.dir/build.make:97: recipe for target 'cmTC_15b4a' failed
make[1]: *** [cmTC_15b4a] Error 1
make[1]: Leaving directory '/home/ilya/p4/p4c/build/CMakeFiles/CMakeTmp'
Makefile:126: recipe for target 'cmTC_15b4a/fast' failed
make: *** [cmTC_15b4a/fast] Error 2

[antoninbas]

This is not an error. See #1534 (comment)
The real error should be displayed in the cmake output. That fragment of CMakeError.log is not useful.

[ilya-ratner]

It's not a fragment; it's an entire CMakeError.log.
If it's not an error, then why doesn't subsequent 'make -j4' work? True, CMakeOutput.log doesn't show any errors. I am just following the instructions here. All dependencies have been installed successfully.

I can see why there's an issue: it looks for 'libpthreads' -- and there's no such library; it's 'libpthread'.

[antoninbas]

There should be some errors before the output you shared:

-- Found LLVM 3.8.0
-- Added 14 tests to 'ebpf-bcc' (0 xfails)
-- Added 14 tests to 'ebpf' (0 xfails)
-- Added 5 tests to 'p4' (0 xfails)
-- Added 533 tests to 'p4' (5 xfails)
-- Added 5 tests to 'err' (0 xfails)
-- Added 160 tests to 'err' (0 xfails)
-- Added 207 tests to 'p14_to_16' (0 xfails)
-- CTest parallel: -j 4
-- Configuring incomplete, errors occurred!

[jafingerhut]

I do not know why this message is appearing, but if you are willing to start from a freshly installed Ubuntu 16.04 or 18.04 Linux system, the script [1] can install p4c and its needed dependencies, and the script [2] installs those plus BMv2 plus open source P4Runtime API software. They do not do anything more than the README instructions say to do, but they can help the process be more reproducible across installs.

[1] https://github.com/jafingerhut/p4-guide/blob/master/bin/install-p4c-without-bmv2.sh
[2] https://github.com/jafingerhut/p4-guide/blob/master/bin/install-p4dev-p4runtime.sh

[ilya-ratner]

Yes, starting from fresh again is plan c :). This is a brand new install of Ubuntu 16.04. And, seemingly, everything was working fine -- got all the dependencies, built protobuf, etc.
Here's the entirety of cmake output:
(and I notice that there's an error; not sure what it means)
ilya@ilya-virtual-machine:~/p4/p4c/build$ cmake ..
-- Boost version: 1.58.0
-- Found the following Boost libraries:
-- iostreams
-- regex
-- Program 'simple_switch_CLI' (https://github.com/p4lang/behavioral-model.git) not found;
Searched .
Will not run BMv2 tests. (missing: SIMPLE_SWITCH SIMPLE_SWITCH_CLI)
-- Program 'psa_switch_CLI' (https://github.com/p4lang/behavioral-model.git) not found;
Searched .
Will not run PSA BMv2 tests. (missing: PSA_SWITCH PSA_SWITCH_CLI)
-- Using the GNU gold linker.
-- Available extensions
CMake Warning at backends/bmv2/CMakeLists.txt:189 (MESSAGE):
BMv2 simple switch is not available, not adding v1model BMv2 tests

CMake Warning at backends/bmv2/CMakeLists.txt:195 (MESSAGE):
BMv2 PSA switch is not available, not adding PSA BMv2 tests

CMake Warning at backends/ebpf/CMakeLists.txt:102 (MESSAGE):
Kernel version 4.10.0 too small, expected 4.15.0. Ignoring ebpf kernel
tests...

CMake Error at /usr/share/llvm-3.8/cmake/LLVMConfig.cmake:178 (include):
include could not find load file:

/usr/share/llvm/cmake/LLVMExports.cmake

Call Stack (most recent call first):
backends/ebpf/CMakeLists.txt:111 (find_package)

CMake Error at /usr/share/llvm-3.8/cmake/LLVMConfig.cmake:181 (include):
include could not find load file:

/usr/share/llvm/cmake/LLVM-Config.cmake

Call Stack (most recent call first):
backends/ebpf/CMakeLists.txt:111 (find_package)

-- Found LLVM 3.8.0
-- Added 14 tests to 'ebpf-bcc' (0 xfails)
-- Added 14 tests to 'ebpf' (0 xfails)
-- Added 5 tests to 'p4' (0 xfails)
-- Added 533 tests to 'p4' (5 xfails)
-- Added 5 tests to 'err' (0 xfails)
-- Added 160 tests to 'err' (0 xfails)
-- Added 207 tests to 'p14_to_16' (0 xfails)
-- CTest parallel: -j 4
-- Configuring incomplete, errors occurred!
See also "/home/ilya/p4/p4c/build/CMakeFiles/CMakeOutput.log".
See also "/home/ilya/p4/p4c/build/CMakeFiles/CMakeError.log".

[mihaibudiu]

It looks like you have hit this issue: #1376
There is no simple solution; the issue links to a solution which requires you to edit some llvm configuration files.

[ilya-ratner]

Yep, that's it looks like! Thanks for the link. I will plod along.

[ilya-ratner]

And thanks to antoninbas -- -DENABLE_EBPF=OFF seems to have done the trick.

[mihaibudiu]

Hopefully the LLVM issue has been solved, so I am closing this one.