c++ - 编译包含结构的 h 文件时出现链接错误

Question

我有这个 ProcessStasts.h 文件，它包含在另外两个 .h 文件中。

#pragma once

#include <mpi.h>
#include <cstddef>

struct ProcessStats
{
    int rank,
    itLeft,
    crtIt,
    processFlag;
    float speed;
};

MPI_Datatype MPI_Cust_ProcessStats_create()
{
    // set data to create new MPI data type
    MPI_Datatype MPI_Cust_ProcessStats;
    MPI_Datatype dataTypes[5] = {MPI_INT, MPI_INT, MPI_INT, MPI_INT, MPI_FLOAT};
    int blockLengths[5] = {1, 1, 1, 1, 1};
    MPI_Aint offsets[5];

    offsets[0] = (MPI_Aint) offsetof(ProcessStats, rank);
    offsets[1] = (MPI_Aint) offsetof(ProcessStats, itLeft);
    offsets[2] = (MPI_Aint) offsetof(ProcessStats, crtIt);
    offsets[3] = (MPI_Aint) offsetof(ProcessStats, processFlag);
    offsets[4] = (MPI_Aint) offsetof(ProcessStats, speed);

    // create new MPI type based on data from above
    MPI_Type_create_struct(5, blockLengths, offsets, dataTypes, &MPI_Cust_ProcessStats);
    MPI_Type_commit(&MPI_Cust_ProcessStats);

    return MPI_Cust_ProcessStats;
}

当我尝试编译时出现此错误:error LNK2005: MPI_Cust_ProcessStats_create(void) already defined。如果我从其中一个文件注释 #include "ProcessStasts.h" 指令和使用 ProcessStats 结构的行，它会正确编译。我什至试图评论所有依赖于 ProcessStats 的行，只留下 #include "ProcessStasts.h" 语句，我得到了这个 lnk 错误。怎么了？

Answer 1

你可以这样写:首先是 ProcessStasts.h

#pragma once

#include <mpi.h>
#include <cstddef>

struct ProcessStats
{
    int rank,
    itLeft,
    crtIt,
    processFlag;
    float speed;
};

MPI_Datatype MPI_Cust_ProcessStats_create();

然后是ProcessStasts.c

#include "ProcessStats.h"
MPI_Datatype MPI_Cust_ProcessStats_create()
{
    // set data to create new MPI data type
    MPI_Datatype MPI_Cust_ProcessStats;
    MPI_Datatype dataTypes[6] = {MPI_INT, MPI_INT, MPI_INT, MPI_INT, MPI_FLOAT};
    int blockLengths[5] = {1, 1, 1, 1, 1};
    MPI_Aint offsets[5];

    offsets[0] = (MPI_Aint) offsetof(ProcessStats, rank);
    offsets[1] = (MPI_Aint) offsetof(ProcessStats, itLeft);
    offsets[2] = (MPI_Aint) offsetof(ProcessStats, crtIt);
    offsets[3] = (MPI_Aint) offsetof(ProcessStats, processFlag);
    offsets[4] = (MPI_Aint) offsetof(ProcessStats, speed);

    // create new MPI type based on data from above
    MPI_Type_create_struct(3, blockLengths, offsets, dataTypes, &MPI_Cust_ProcessStats);
    MPI_Type_commit(&MPI_Cust_ProcessStats);

    return MPI_Cust_ProcessStats;
}

然后您可以根据需要多次包含 ProcessStasts.h。建议不要在头文件中定义函数。