c++ Pin shared library undefined symbol

Question

I am using the Intel Pin tool to generate a shared object file from a C source file and a C++ pintool. I have used the following g++ commands to generate my shared object file. Apologies in advance as the commands are very big due to the Pin libraries and options.

g++ -DBIGARRAY_MULTIPLIER=1 -Wall -Werror -Wno-unknown-pragmas -D__PIN__=1 -DPIN_CRT=1  -fno-stack-protector -fno-exceptions -funwind-tables -fasynchronous-unwind-tables -fno-rtti -DTARGET_IA32E -DHOST_IA32E -fPIC -DTARGET_LINUX -fabi-version=2  -I/home/rohit/github_repos/uli/src/pin/pin-3.2-81205-gcc-linux/source/include/pin -I/home/rohit/github_repos/uli/src/pin/pin-3.2-81205-gcc-linux/source/include/pin/gen -isystem /home/rohit/github_repos/uli/src/pin/pin-3.2-81205-gcc-linux/extras/stlport/include -isystem /home/rohit/github_repos/uli/src/pin/pin-3.2-81205-gcc-linux/extras/libstdc++/include -isystem /home/rohit/github_repos/uli/src/pin/pin-3.2-81205-gcc-linux/extras/crt/include -isystem /home/rohit/github_repos/uli/src/pin/pin-3.2-81205-gcc-linux/extras/crt/include/arch-x86_64 -isystem /home/rohit/github_repos/uli/src/pin/pin-3.2-81205-gcc-linux/extras/crt/include/kernel/uapi -isystem /home/rohit/github_repos/uli/src/pin/pin-3.2-81205-gcc-linux/extras/crt/include/kernel/uapi/asm-x86 -I/home/rohit/github_repos/uli/src/pin/pin-3.2-81205-gcc-linux/extras/components/include -I/home/rohit/github_repos/uli/src/pin/pin-3.2-81205-gcc-linux/extras/xed-intel64/include/xed -Iinc -I/home/rohit/github_repos/uli/src/pin/pin-3.2-81205-gcc-linux/source/tools/InstLib -O0   -c -o obj-intel64/testcpp.o testcpp.cpp

g++ -DBIGARRAY_MULTIPLIER=1 -Wall -Werror -Wno-unknown-pragmas -D__PIN__=1 -DPIN_CRT=1  -fno-stack-protector -fno-exceptions -funwind-tables -fasynchronous-unwind-tables -fno-rtti -DTARGET_IA32E -DHOST_IA32E -fPIC -DTARGET_LINUX -fabi-version=2  -I/home/rohit/github_repos/uli/src/pin/pin-3.2-81205-gcc-linux/source/include/pin -I/home/rohit/github_repos/uli/src/pin/pin-3.2-81205-gcc-linux/source/include/pin/gen -isystem /home/rohit/github_repos/uli/src/pin/pin-3.2-81205-gcc-linux/extras/stlport/include -isystem /home/rohit/github_repos/uli/src/pin/pin-3.2-81205-gcc-linux/extras/libstdc++/include -isystem /home/rohit/github_repos/uli/src/pin/pin-3.2-81205-gcc-linux/extras/crt/include -isystem /home/rohit/github_repos/uli/src/pin/pin-3.2-81205-gcc-linux/extras/crt/include/arch-x86_64 -isystem /home/rohit/github_repos/uli/src/pin/pin-3.2-81205-gcc-linux/extras/crt/include/kernel/uapi -isystem /home/rohit/github_repos/uli/src/pin/pin-3.2-81205-gcc-linux/extras/crt/include/kernel/uapi/asm-x86 -I/home/rohit/github_repos/uli/src/pin/pin-3.2-81205-gcc-linux/extras/components/include -I/home/rohit/github_repos/uli/src/pin/pin-3.2-81205-gcc-linux/extras/xed-intel64/include/xed -Iinc -I/home/rohit/github_repos/uli/src/pin/pin-3.2-81205-gcc-linux/source/tools/InstLib -O0   -c -o obj-intel64/test.o test.c

g++ -shared -Wl,-z,defs -Wl,--hash-style=sysv /home/rohit/github_repos/uli/src/pin/pin-3.2-81205-gcc-linux/intel64/runtime/pincrt/crtbeginS.o -Wl,-Bsymbolic -Wl,--version-script=/home/rohit/github_repos/uli/src/pin/pin-3.2-81205-gcc-linux/source/include/pin/pintool.ver -fabi-version=2   obj-intel64/testcpp.so -o obj-intel64/testcpp.o obj-intel64/test.o  -L/home/rohit/github_repos/uli/src/pin/pin-3.2-81205-gcc-linux/intel64/runtime/pincrt -L/home/rohit/github_repos/uli/src/pin/pin-3.2-81205-gcc-linux/intel64/lib -L/home/rohit/github_repos/uli/src/pin/pin-3.2-81205-gcc-linux/intel64/lib-ext -L/home/rohit/github_repos/uli/src/pin/pin-3.2-81205-gcc-linux/extras/xed-intel64/lib -lpin -lxed /home/rohit/github_repos/uli/src/pin/pin-3.2-81205-gcc-linux/intel64/runtime/pincrt/crtendS.o -lpin3dwarf  -ldl-dynamic -nostdlib -lstlport-dynamic -lm-dynamic -lc-dynamic -lunwind-dynamic

testcpp.cpp is my C++ pintool and test.c is my C source file. The folder inc contains the header file test.h which is included in both of them.

This is my C++ file -

#include "pin.H"
#include <iostream>
#include <fstream>

extern "C" {
#include <test.h>
}

using namespace std;

KNOB<string> KnobOutputFile(KNOB_MODE_WRITEONCE, "pintool", "o", "test.out","This pin tool simulates ULI");

FILE * op;

VOID Instruction(INS ins, void *v) {
}

VOID Fini(INT32 code, VOID *v) {
    fprintf(op,"Ended from c++\n");
    fprintf(op,"%d\n",cfunc(11,2));
    fclose(op);
}

INT32 Usage() {
    PIN_ERROR("This Pintool failed\n" + KNOB_BASE::StringKnobSummary() + "\n");
    return -1;
}

int main(int argc, char *argv[]) {

    if (PIN_Init(argc, argv)) 
        return Usage();

    op = fopen("test.out", "w");

    PIN_InitSymbols();
    INS_AddInstrumentFunction(Instruction, 0);
    PIN_AddFiniFunction(Fini, 0);
    PIN_StartProgram();

    return 0;
}

This is my C file-

#include <stdio.h>
#include <test.h>

int cfunc(int a, int b)
{
    return(a+b);
}

void cfunc2()
{
    printf("Hello from C %d\n",cfunc(3,5));
}

This is my test.h file-

int cfunc(int, int);
void cfunc2(void);

The rest of the options are pin specific and I simply used them from the sample programs and feel that they don't need modifications (I hope so!)

However when I generate my shared object file I get this error-

obj-intel64/testcpp.o: In function `Fini(int, void*)':
testcpp.cpp:(.text+0x41): undefined reference to `cfunc2'
collect2: error: ld returned 1 exit status

cfunc2 is the function I am trying to call. I do not understand where I am going wrong. I am including the right options and arguments, but somehow this symbol is undefined. Any suggestions?

Answer 1

You use g++ to compile the test.c file. The g++ compiler driver invokes the C++ compiler for .c files, so your functions will have C++ linkage, not C linkage. There are several ways to address thos:

• Compile test.c with gcc instead of g++ .
• Drop the extern "C" from the C++ source file, so that C++ linkage is used everywhere.
• Put the extern "C" into the header file, so that applies to the definition in test.c , too.