[LLVMdev] Problem executing code with lli...

[Frits van Bommel]

Karhu, Abhinav R wrote:
> Hi all,
> I am facing new problem with lli now. I am having a sample code in which I am doing malloc for two variables. If I compile the code with normal gcc the program runs without any warning of any sorts. If I compile the program to convert it into a bytecode file and then run it through lli it segfaults and the program aborts. This is the stack trace after execution.
> lli((anonymous namespace)::PrintStackTrace()+0x1f)[0x67cc7f]
> lli((anonymous namespace)::SignalHandler(int)+0x172)[0x67cf72]
> /lib64/tls/libc.so.6[0x2a95e4b300]
> lli(llvm::ExecutionEngine::LoadValueFromMemory(llvm::GenericValue*, llvm::Type const*)+0x182)[0x4be4f2]
> lli(llvm::InstVisitor<llvm::Interpreter, void>::visit(llvm::Instruction&)+0x1fe)[0x4b648e]
> lli(llvm::Interpreter::run()+0x2b)[0x4b179b]
> lli(llvm::Interpreter::runFunction(llvm::Function*, std::vector<llvm::GenericValue, std::allocator<llvm::GenericValue> > const&)+0xac)[0x4b490c]
> lli(llvm::ExecutionEngine::runFunctionAsMain(llvm::Function*, std::vector<std::basic_string<char, std::char_traits<char>, std::allocator<char> >, std::allocator<std::basic_string<char, std::char_traits<char>, std::allocator<char> > > > const&, char const* const*)+0xa5)[0x4bf295]
> lli(main+0x170)[0x4aaac0]
> /lib64/tls/libc.so.6(__libc_start_main+0xdb)[0x2a95e3940b]
> lli(__gxx_personality_v0+0xda)[0x4aa87a]
> Segmentation fault
> 
> I am also testing to see if the malloc was successful or not and it shows that malloc was successful. 
> 
> The part where is static memory is allocated runs fine(I am putting a print for that value). Why is the program failing in LoadValueFromMemory?
> 
> Please some light on this issue.

First of all, you also sent this to me personally. Rest assured I'm 
(obviously) on this list and if I see a problem I think I can help with 
I will reply here. No need to mail me personally.

Now then, I think a problem like this is probably not easy to solve from 
just a stack trace. Try reducing your program to the minimum that will 
still produce the crash[1] and (assuming you still can't see any obvious 
problems in it by yourself at that point) then putting it (in .ll or .bc 
form) in a problem report[2] (through http://llvm.org/bugs/) or (if it's 
small) pasting it (in .ll form) into a post to LLVM-Dev.


[1]: I gather "bugpoint" may be of use in these situations.
[2]: If you go the problem report route, try using the search 
functionality first to see if there's already a report by someone else 
on the same issue.