[LLVMdev] Problems accessing structs

[John Criswell]

Anders Alexandersson wrote:
> Hello!
> 
> I get some odd behaviour using my structs:
> 
> "myKernelMap" = type {int (sbyte*)*, int ()*}
> "Kernel" = type {"myKernelMap"*}
> 
> The second member (  int()*  ) is a pointer to the %getchar() function.
> 
> I want to call getchar using this function:
> 
> int "callmyKernelgetchar_kernel"("Kernel"* "myKernel")
> {
>         "PTRMAP" = getelementptr "Kernel"* "myKernel", long 0, ubyte 0
> "MAP" = load "myKernelMap"** "PTRMAP"
> "getchar_kernelPTR" = getelementptr "myKernelMap"* "MAP", long 0, ubyte 1
> %tmp = load int ()** "getchar_kernelPTR"
> "tmp_result" = call int ()* %tmp()
> ret int "tmp_result"
> }
> 
> I call it from main():
> 
> int %main() {
> ;Malloc's a Kernel and returns a pointer to it
> "myKernel" = call "Kernel"* "createKernel"()
> 
> call int "callmyKernelgetchar_kernel"("Kernel"* "myKernel")
> ret int 0
> }
> 
> 
> I get this output error message:
> 
> Hello Kernel
> lli[0x844dd24]
> lli[0x844df30]
> /lib/tls/libc.so.6[0x420275c8]
> 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*)+0x25b)[0x8305ca5]
> lli(main+0x23c)[0x82aa058]
> /lib/tls/libc.so.6(__libc_start_main+0xe4)[0x42015574]
> lli(dlopen+0x41)[0x82a9d8d]
> Segmentation fault
> 
> I have tried to have different function pointers, but ONLY pointers in position 0 in the map-struct works. If I try to access any other posistion, e.g. long 0, ubyte 1, this error comes.
> 
> What is wrong? Getelementptr again? :)
> 
> The detailed complete source code is below.
> 
> Regards
> Anders
> 
> -----
> 
> "Hello KernelConst" = internal constant  [14 x sbyte ] c"Hello Kernel\0A\00"
> 
> "myKernelMap" = type {int (sbyte*)*, int ()*}
> "Kernel" = type {"myKernelMap"*}
> 
> declare int %printf(sbyte*, ...)
> declare int %getchar(...)
> 
> int %puts_kernel(sbyte* %string)
> {
> %tmp0 = call int (sbyte*, ...)* %printf(sbyte* %string)
> ret int 0
> }
> 
> int %getchar_kernel()
> {
> %tmp0 = call int (...)* %getchar()
> ret int 0
> }
> 
> "Kernel"* "createKernel"()
> {
> "myKernelMapInstance" = malloc "myKernelMap"
> "myKernel" = malloc "Kernel"
> "myKernelMapPTR" = getelementptr "Kernel"* "myKernel", long 0, ubyte 0
> store "myKernelMap"* "myKernelMapInstance", "myKernelMap"** "myKernelMapPTR"
> "puts_kernelPTRPTRMAP" = getelementptr "Kernel"* "myKernel", long 0, ubyte 0
> "puts_kernelPTRMAP" = load "myKernelMap"** "puts_kernelPTRPTRMAP"
> "puts_kernelPTR" = getelementptr "myKernelMap"* "puts_kernelPTRMAP", long 0, ubyte 0
> store int (sbyte*)* %puts_kernel, int (sbyte*)** "puts_kernelPTR"
> ret "Kernel"* "myKernel"
    ^---------------
    + I'm guessing this line might be the problem.
    :)


The initialization code below is never getting reached, so the getchar() 
function pointer is never initialized.

> "getchar_kernelPTRPTRMAP" = getelementptr "Kernel"* "myKernel", long 0, ubyte 0
> "getchar_kernelPTRMAP" = load "myKernelMap"** "getchar_kernelPTRPTRMAP"
> "getchar_kernelPTR" = getelementptr "myKernelMap"* "getchar_kernelPTRMAP", long 0, ubyte 1
> store int ()* %getchar_kernel, int ()** "getchar_kernelPTR"
> ret "Kernel"* "myKernel"
> }
> 
> int "callmyKernelputs_kernel"("Kernel"* "myKernel")
> {
>         "PTRMAP" = getelementptr "Kernel"* "myKernel", long 0, ubyte 0
> "MAP" = load "myKernelMap"** "PTRMAP"
> "puts_kernelPTR" = getelementptr "myKernelMap"* "MAP", long 0, ubyte 0
> %tmp = load int (sbyte*)** "puts_kernelPTR"
> "Hello Kernel" = getelementptr [14 x sbyte]* "Hello KernelConst", long 0, long 0
> "tmp_result" = call int (sbyte*)* %tmp(sbyte* "Hello Kernel")
> ret int "tmp_result"
> }
> 
> int "callmyKernelgetchar_kernel"("Kernel"* "myKernel")
> {
>         "PTRMAP" = getelementptr "Kernel"* "myKernel", long 0, ubyte 0
> "MAP" = load "myKernelMap"** "PTRMAP"
> "getchar_kernelPTR" = getelementptr "myKernelMap"* "MAP", long 0, ubyte 1
> %tmp = load int ()** "getchar_kernelPTR"
> "tmp_result" = call int ()* %tmp()
> ret int "tmp_result"
> }
> 
> int %main() {
> "myKernel" = call "Kernel"* "createKernel"()
> call int "callmyKernelputs_kernel"("Kernel"* "myKernel")
> call int "callmyKernelgetchar_kernel"("Kernel"* "myKernel")
> "myKernel_MapPTRPTR" = getelementptr "Kernel"* "myKernel", long 0, ubyte 0
> "myKernel_MapPTR" = load "myKernelMap"** "myKernel_MapPTRPTR"
> free "myKernelMap"* "myKernel_MapPTR"
> free "Kernel"* "myKernel"
> ret int 0
> }
> 
> 
> ----------------------------------------------------------------
> Anders Alexandersson
> Masters student at the special year of Software Engineering, HTU Trollhättan
> E-mail: anders.alexandersson at student.htu.se
> 
> _______________________________________________
> LLVM Developers mailing list
> LLVMdev at cs.uiuc.edu         http://llvm.cs.uiuc.edu
> http://mail.cs.uiuc.edu/mailman/listinfo/llvmdev


-- John T.

-- 
*********************************************************************
* John T. Criswell                         Email: criswell at uiuc.edu *
* Research Programmer                                               *
* University of Illinois at Urbana-Champaign                        *
*                                                                   *
* "It's today!" said Piglet. "My favorite day," said Pooh.          *
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