的malloc分配內存的列表

Question

我有一個自定義結構

typedef struct node 
{ 

    struct node *next; 
    int vertex; 
}node; 

typedef struct { 

    int numberOfNodes; 
    int *visited; 
    int numberOfEdges ; 

    node **ppLists; 
} adjacencyList; 

我想對鄰接表與numberOfNodes下面的代碼爲1000。

adjacencyList *createAdjList(int numberOfNodes) 
{ 
    int i; 
    adjacencyList *newList; 

    //Allocate memory for list and the array of nodes 

    newList=(adjacencyList *)malloc(sizeof(adjacencyList)); 
    newList->numberOfNodes=numberOfNodes; 
    newList->ppLists=(node**)malloc(numberOfNodes*sizeof(node)); 


    for (i = 0; i < newList->numberOfNodes; i++) { 
     newList->ppLists[i] = (node*)malloc(sizeof(node)*newList->numberOfNodes); 
    } 

    return newList; 
} 

的代碼分配內存順利地順從，但是我在運行時遇到了分段錯誤。我使用了gdb，這是後面的跟蹤。

#0 0x00007ffff7a51425 in __GI_raise (sig=<optimized out>) at ../nptl/sysdeps/unix/sysv/linux/raise.c:64 
#1 0x00007ffff7a54b8b in __GI_abort() at abort.c:91 
#2 0x00007ffff7a9915d in __malloc_assert (assertion=<optimized out>, file=<optimized out>, line=<optimized out>, function=<optimized out>) at malloc.c:300 
#3 0x00007ffff7a9c674 in sYSMALLOc (av=0x7ffff7dd3720, nb=16016) at malloc.c:2448 
#4 _int_malloc (av=0x7ffff7dd3720, bytes=16000) at malloc.c:3903 
#5 0x00007ffff7a9dfc5 in __GI___libc_malloc (bytes=16000) at malloc.c:2924 
#6 0x0000000000401c08 in createAdjList (numberOfNodes=1000) at /home/merlyn/projects/soft/AdjacencyList.c:25 
#7 0x0000000000401155 in createAdjListFromMatrix (pAdjMatrix=0x605010) at /home/merlyn/projects/soft/tools.c:86 
#8 0x0000000000401017 in main (argc=2, argv=0x7fffffffdf18) at /home/merlyn/projects/soft/main.c:22 

的valgrind

==6328== Memcheck, a memory error detector 
==6328== Copyright (C) 2002-2011, and GNU GPL'd, by Julian Seward et al. 
==6328== Using Valgrind-3.7.0 and LibVEX; rerun with -h for copyright info 
==6328== Command: ./exercise 
==6328== 
==6328== Invalid write of size 4 
==6328== at 0x4E8892D: _IO_vfscanf (vfscanf.c:1857) 
==6328== by 0x4E903EA: __isoc99_fscanf (isoc99_fscanf.c:35) 
==6328== by 0x401A15: readAdjMatrixFromFile (AdjacencyMatrix.c:138) 
==6328== by 0x400FF5: main (main.c:14) 
==6328== Address 0x51f3675 is 997 bytes inside a block of size 1,000 alloc'd 
==6328== at 0x4C2B6CD: malloc (in /usr/lib/valgrind/vgpreload_memcheck-amd64-linux.so) 
==6328== by 0x4019AA: readAdjMatrixFromFile (AdjacencyMatrix.c:126) 
==6328== by 0x400FF5: main (main.c:14) 
==6328== 
1000 
==6328== Conditional jump or move depends on uninitialised value(s) 
==6328== at 0x401D68: addEdgeToAdjList (AdjacencyList.c:75) 
==6328== by 0x4011A5: createAdjListFromMatrix (tools.c:77) 
==6328== by 0x401016: main (main.c:22) 
==6328== 
==6328== 
==6328== HEAP SUMMARY: 
==6328==  in use at exit: 17,098,448 bytes in 7,154 blocks 
==6328== total heap usage: 7,156 allocs, 2 frees, 17,099,584 bytes allocated 
==6328== 
==6328== LEAK SUMMARY: 
==6328== definitely lost: 48 bytes in 2 blocks 
==6328== indirectly lost: 17,098,400 bytes in 7,152 blocks 
==6328==  possibly lost: 0 bytes in 0 blocks 
==6328== still reachable: 0 bytes in 0 blocks 
==6328==   suppressed: 0 bytes in 0 blocks 
==6328== Rerun with --leak-check=full to see details of leaked memory 
==6328== 
==6328== For counts of detected and suppressed errors, rerun with: -v 
==6328== Use --track-origins=yes to see where uninitialised values come from 
==6328== ERROR SUMMARY: 3994 errors from 2 contexts (suppressed: 2 from 2 

主要.C

#include "AdjacencyList.h" 
#include "AdjacencyMatrix.h" 
#include "tools.h" 

#include <stdio.h> 
#include <stdlib.h> 


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

    // load the matrix 

    adjacencyMatrix *newAdjMatrix=readAdjMatrixFromFile(argv[1]) ; 

    // A test to check if the matrix has actually been loaded 

    writeAdjMatrixToFile(newAdjMatrix, "123.txt"); 

    // covert matrix to list 

    adjacencyList *newAdjList = createAdjListFromMatrix(newAdjMatrix); 

    // perform reachablity for matrix 

    //checkReachabilityMatrix(newAdjMatrix,0) ; 

    // perform reachability for list 

    return 0; 
} 

adjacencyMatrix *readAdjMatrixFromFile(char *pFilename) 
{ 

    adjacencyMatrix *newAdjMatrix; 
    newAdjMatrix = (adjacencyMatrix *) malloc(sizeof(adjacencyMatrix)); 
    FILE *pFile; 
    pFile = fopen("/home/merlyn/projects/soft/Graph.txt", "r"); 
    char ch; 

    if(pFile==NULL) 
    { 
     printf("Cannot open File"); 

    } 
    //First Character will have number of nodes 
    int i,j; 
    //fgetc(
    fscanf(pFile, "%d",&i); 

    //newAdjMatrix->numberOfNodes=((int)fgetc(pFile)); 

    newAdjMatrix->numberOfNodes = i; 
    newAdjMatrix->ppMatrix = (bool**) malloc(sizeof(bool*)*newAdjMatrix->numberOfNodes); 

    int idx; 
    for (idx = 0; idx < newAdjMatrix->numberOfNodes; idx++) 
     newAdjMatrix->ppMatrix[idx] = (bool*) malloc(sizeof(bool)*newAdjMatrix->numberOfNodes); 

    i=0;//rows 
    j=0;//columns 
    //iterate over entire file 
    for(i=0;i<newAdjMatrix->numberOfNodes;i++) 
    { 
     for(j=0;j<newAdjMatrix->numberOfNodes;j++) 

     //keep adding elements to the column for ith row 
      fscanf(pFile, "%d",&newAdjMatrix->ppMatrix[i][j]); 

    } 

    fclose(pFile); 
    return newAdjMatrix; 
} 

typedef struct 
{ 

    int numberOfNodes; 

    bool **ppMatrix; 
} adjacencyMatrix; 

tools.c

adjacencyList *createAdjListFromMatrix(adjacencyMatrix *pAdjMatrix) 
{ 
    //create a adjacencyList with the same number of nodes as adjacencyMatrix 

    adjacencyList *pNewadjacencyList=createAdjList(pAdjMatrix->numberOfNodes); 

    // now we move from row to row and create a list for every 1 
    int i,j; 

    for(i=0;i<pAdjMatrix->numberOfNodes;i++) 
    { 
     for(j=0;j<pAdjMatrix->numberOfNodes;j++) 
     { 
      //If an edge is found then create a node 
      if(pAdjMatrix->ppMatrix[i][j]==1) 
      { 
       addEdgeToAdjList(pNewadjacencyList, i, j); 

      } 

     } 
    } 
    return pNewadjacencyList; 
} 

Answer 1

這條線的位置：

newList->ppLists=(node**)malloc(numberOfNodes*sizeof(node)); 

應改爲：

newList->ppLists = malloc(numberOfNodes*sizeof(node*)); 

的原因是，你有一個指針數組節點。所以這個數組的實際類型是一個指向節點的指針（node*）。這是你想要分配內存的類型。之後，malloc已分配的內存會返回一個指向該類型的，所以你會得到一個指向指針= node**

在C你沒有投用malloc不像C++

Answer 2

這裏返回void *：

newList->ppLists=(node**)malloc(numberOfNodes*sizeof(node));

你問到的malloc返回一個指向某些節點。但是，因爲你有一個聲明是指針爲ppLists指針要在下列方式的malloc（考慮到H2CO3的建議不投結果）：

newList->ppLists = malloc(numberOfNodes * sizeof *newList->ppLists);

這是問的malloc給你返回指向node類型的結構的指針數組，而不是所述結構體的數組。