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I have a small C++ test project which should result in a .so-library on Windows Subsystem for Linux (WSL, more or less = Ubuntu 14.x). In order to get a PHP extension the current version of the PHP-CPP library is linked to the project. The compiler is g++ 4.8 on Linux and remotely operated from Visual Studio. In the properties I add -fpic for compiling and -lphpcpp to link libphpcpp.so. Using the old version of Visual Studio 2017 (until 02/2018) everything behaved well and the build was fine.

After updating to the current version of Visual Studio 2017 (15.5.6, 02/2018) the build ends in numerous linking errors of the same type: /usr/bin/ld : error : relocation x has invalid symbol index y, where the numbers x and y vary. I have no idea what happens here.

The small project consists uses the ideas from here:

DLL in Visual Studio ... and ... PHP-CPP first extension

The linking options recorded in Visual Studio:

-o"C:\Users\Robert\Documents\Lightning Talk\MathFuncs\MathFuncs\bin\x64\Release\MathFuncs.out" "3600000" 
-Wl,-z,relro -Wl,--print-map -Wl,-z,noexecstack -Wl,--trace -Wl,
--verbose -Wl,--no-undefined "g++" -l"phpcpp" -Wl,-z,now

The last lines of the ld/g++ error messages:

1>/usr/bin/ld : error : relocation 15 has invalid symbol index 13
1>/usr/bin/ld : error : relocation 16 has invalid symbol index 13
1>/usr/bin/ld : error : relocation 17 has invalid symbol index 13
1>/usr/bin/ld : error : relocation 18 has invalid symbol index 13
1>/usr/bin/ld : error : relocation 19 has invalid symbol index 21
1>/usr/bin/ld : error : relocation 0 has invalid symbol index 2
1>/usr/lib/gcc/x86_64-linux-gnu/4.8/../../../x86_64-linux-gnu/crt1.o : error :
1>collect2 : error : ld returned 1 exit status
1>Die Erstellung des Projekts "MathFuncs.vcxproj" ist abgeschlossen -- FEHLER.

My code is here: MathFuncs.h:

#pragma once
#include <stdexcept>

using namespace std;

// This class is exported from the MathFuncsDll.dll
class MathFuncs
{
public:
    // Returns a + b
    static double Add(double a, double b);

    // Returns a - b
    static double Subtract(double a, double b);

    // Returns a * b
    static double Multiply(double a, double b);

    // Returns a / b
    // Throws const std::invalid_argument& if b is 0
    static double Divide(double a, double b);
};





double MathFuncs::Add(double a, double b)
{
    return a + b;
}

double MathFuncs::Subtract(double a, double b)
{
    return a - b;
}

double MathFuncs::Multiply(double a, double b)
{
    return a * b;
}

double MathFuncs::Divide(double a, double b)
{
    if (b == 0)
    {
        throw invalid_argument("b cannot be zero!");
    }

    return a / b;
}

... and main.cpp:

#include <iostream>
#include <phpcpp.h>
#include "MathFuncs.h"

Php::Value  phpAdd(Php::Parameters &params)
{

    auto a(0.0);
    a = params[0];

    auto b(0.0);
    b = params[1];

    return MathFuncs::Add(a, b);
}

Php::Value phpSubtract(Php::Parameters &params)
{
    auto a(0.0);
    a = params[0];

    auto b(0.0);
    b = params[1];

    return MathFuncs::Subtract(a, b);
}

Php::Value phpMultiply(Php::Parameters &params)
{
    auto a(0.0);
    a = params[0];

    auto b(0.0);
    b = params[1];

    return MathFuncs::Multiply(a, b);
}

Php::Value phpDivide(Php::Parameters &params)
{
    auto a(0.0);
    a = params[0];

    auto b(0.0);
    b = params[1];

    return MathFuncs::Divide(a, b);
}

extern "C" {

    /**
    *  Function that is called by PHP right after the PHP process
    *  has started, and that returns an address of an internal PHP
    *  strucure with all the details and features of your extension
    *
    *  @return void*   a pointer to an address that is understood by PHP
    */
    PHPCPP_EXPORT void *get_module()
    {
        // static(!) Php::Extension object that should stay in memory
        // for the entire duration of the process (that's why it's static)
        static Php::Extension extension("phpMathFuncs", "1.0"); // To be         humble, we can change the version number to 0.0.1

        extension.add<phpAdd>("Add", {
            Php::ByVal("a", Php::Type::Float),
            Php::ByVal("b", Php::Type::Float)
            });

        extension.add<phpSubtract>("Subtract", {
            Php::ByVal("a", Php::Type::Float),
            Php::ByVal("b", Php::Type::Float)
            });

        extension.add<phpMultiply>("Multiply", {
            Php::ByVal("a", Php::Type::Float),
            Php::ByVal("b", Php::Type::Float)
            });

        extension.add<phpDivide>("Divide", {
            Php::ByVal("a", Php::Type::Float),
            Php::ByVal("b", Php::Type::Float)
            });

        // return the extension
        return extension;
    }
}
Robert
  • 97
  • 6

1 Answers1

0

In the project properties/general the had been "application (.out)". Changing it to "dynamic library (.so)" solved the problem.

Robert
  • 97
  • 6