in my embedded program I have several "configuration objects" which alow user to configure its device. All of these objects are const (with pointer to memory which can ,c++,linker,attributes,sections"/>

时间戳

首页 > 解决方案 > GCC 链接器将变量与 causes a section type conflict with

in my embedded program I have several "configuration objects" which alow user to configure its device. All of these objects are const (with pointer to memory which can

c++ - GCC 链接器将变量与 causes a section type conflict with

in my embedded program I have several "configuration objects" which alow user to configure its device. All of these objects are const (with pointer to memory which can

问题描述

in my embedded program I have several "configuration objects" which alow user to configure its device. All of these objects are const (with pointer to memory which can be configured) and are put into specified section (to have objects from different compilation units in one place). The structure and example of such object is as follows:

class CObjectParams
{
public:
   OMB::ObjectId  ObjectID;
   TMODULE_ID     ModuleID;
   void*          pData;
   unsigned short u16Length;

   TAccessControl AccessControl;

   CConverter*    pConverter;


   int ReadObject(void* pDataDestination) const;
   int WriteObject(void* pDataSource) const;
};

Example:

const volatile TSoftwareDescriptor* const BootloaderSoftwareDescriptor = (const volatile TSoftwareDescriptor* const) (FLASH_BASE + DESCRIPTOR_OFFSET);

const CObjectParams __attribute__((used, section("_objects_section"))) BootloaderSoftwareVersionObjectParams =
{
   OMB::ObjectId::BOOTLOADER_SOFTWARE_VERSION,
   TMODULE_ID::MODULE_ID_FIRMWARE,
   (void*) &BootloaderSoftwareDescriptor->u32FirmwareVersion,
   sizeof(BootloaderSoftwareDescriptor->u32FirmwareVersion),
   {
      (ACCESS_READ),
      LOCATION_DIRECT,
      FIXED_LENGTH,
   },
   nullptr,
};

The problem, I think, is that linker cannot resolve &BootloaderSoftwareDescriptor->u32FirmwareVersion address at link time and therefore tries to put it into .data section to initialize during startup. After lifting section("_objects_section") restriction and analyzing .map file my concerns are confirmed. So why linker cannot resolve mentioned address at link time since BootloaderSoftwareDescriptor is constant pointer and known at compile time?

Here is example code which shows this error:

#include <stdio.h>

#define FIXED_LENGTH     0
#define LOCATION_DIRECT  0
#define ACCESS_READ      0b000010


enum ObjectId : unsigned short
{
    NO_OBJECT = 0x000,

    A,
    B,
    C,
    D
};

enum TMODULE_ID : unsigned short
{
   MODULE_ID_CONFIG                       = 0x00, 
   MODULE_ID_DIAGNOSTICS                  = 0x01,
   MODULE_ID_FIRMWARE                     = 0x04,
};

struct TAccessControl
{
   unsigned char b6Access     : 6;
   unsigned char b4Location   : 2;
   unsigned char b1LengthType : 1;

   unsigned char b7Unused     : 7;
};

class CConverter
{
public:
   virtual void ConvertTo(void* pDestination, void* pSource, int size) {};
   virtual void ConvertFrom(void* pDestination, void* pSource, int size) {};
};

class CObjectParams
{
public:
   ObjectId  ObjectID;
   TMODULE_ID     ModuleID;
   void*          pData;
   unsigned short u16Length;

   TAccessControl AccessControl;

   CConverter*    pConverter;


   int ReadObject(void* pDataDestination) const;
   int WriteObject(void* pDataSource) const;
};

struct TSoftwareDescriptor
{
   unsigned int u32FirmwareCrc;
   unsigned int u32FirmwareSize;
   unsigned int u32HardwareVersion;
   unsigned int u32FirmwareVersion;
   const char S8BuildDate[12];  // Mmm-dd-yyyy\0
   const char S8BuildTime[9];   // HH:mm:ss\0
   unsigned int U32RFU[10] =
   {
      0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
   };
};

#define FLASH_BASE            (0x08000000UL)
#define DESCRIPTOR_OFFSET     50

const volatile TSoftwareDescriptor* const BootloaderSoftwareDescriptor = (const volatile TSoftwareDescriptor* const) (FLASH_BASE + DESCRIPTOR_OFFSET);


const CObjectParams __attribute__((used, section("_objects_section"))) NullObjectParams =
{
   ObjectId::A,
   TMODULE_ID::MODULE_ID_FIRMWARE,
   nullptr,
   sizeof(int),
   {
      (ACCESS_READ),
      LOCATION_DIRECT,
      FIXED_LENGTH,
   },
   nullptr,
};

const CObjectParams __attribute__((used, section("_objects_section"))) BootloaderSoftwareVersionObjectParams =
{
   ObjectId::B,
   TMODULE_ID::MODULE_ID_FIRMWARE,
   (void*) &BootloaderSoftwareDescriptor->u32FirmwareVersion,
   sizeof(BootloaderSoftwareDescriptor),
   {
      (ACCESS_READ),
      LOCATION_DIRECT,
      FIXED_LENGTH,
   },
   nullptr,
};




int main()
{
    printf("%d\n%d\n", NullObjectParams.pData, BootloaderSoftwareVersionObjectParams.pData);
    return 0;
}

This can not be achieved without passing a parameter because it defies the definition/purpose of a Service.

The relationship between services is minimized to the level that they are only aware of their existence.

The consumer/caller/component/service only knows about the existence of the service whereas, the called service knows nothing about who the callee is?

Read detailed information about Services here - https://en.wikipedia.org/wiki/Service-oriented_architecture

标签： c++linkerattributessections

解决方案

推荐阅读