can't load liblagent.so - undefined symbol

[nevgeniev]

hi,

i've tried to compile and load profiler with jdk 1.8.121 got this upon load: Could not find agent library honest-profiler/honest-profiler/build/liblagent.so in absolute path, with error: honest-profiler/honest-profiler/build/liblagent.so: undefined symbol: _ZNVSt6atomicIPN3map9HashTableEE5storeES2_St12memory_order

[daodennis-zz]

What's your -agentpath look like and can you run stat (if this is a linux system) on the location of where liblagent.so is as the user your java program is running?

This is the How to Run for quick reference

[nevgeniev]

I can ldd & stat the library as I built it from source... the thing is I built it with old gcc (4.4.7) /libc... not sure to what degree it could affect the run.. I'm using absolute path.. the problem is not with the library but rather with unknown symbol referenced by library

[ikavalio]

Hey @nevgeniev, I don't think you can compile libagent with gcc's younger than 4.5. I personally used 4.6+ for the development.

[nevgeniev]

this is true unless you define 'nullptr'... once you do you can compile in with gcc older than 4.6

[ikavalio]

@nevgeniev, I believe it's more complicated than just nullptr. Since you're using gcc-4.4 which doesn't have standard c++ atomic's library, cstdatomic will be used instead.

#if __GNUC__ == 4 && __GNUC_MINOR__ < 6 && !defined(__APPLE__) && !defined(__FreeBSD__) && !defined(__clang__)
#   include <cstdatomic>
#else
#   include <atomic>
#endif

Unfortunately it doesn't work well with std::atomic<X> where X is not primitive type, even a pointer to it. Code within concurrent_map.h unfortunately contains:

std::atomic<Job*> job;  
std::atomic<HashTable*> current;

That's why runtime linker is complaining about undefined symbols. It's easy to find them all BTW:

?> ~/w/honest-profiler on master ? nm build/liblagent.so | grep memory_order | grep -e '\bU\b'                    19:20:04
                 U _ZNVSt6atomicIPN3map3JobEE5storeES2_St12memory_order
                 U _ZNVSt6atomicIPN3map9HashTableEE5storeES2_St12memory_order

The only simple solution that can fix this issue is to replace this two variables' type to std::atomic_address (std::atomic<void*>) which is defined in cstdatomic - cstdatomic and cast it to appropriate type like Job* when needed.

I can try to implement this, but don't know how long will it take.

[nitsanw]

Given the fixing PR has been merged I'm closing. Please re-open if the problem persists.