在标题中使用 if 指令

Question

我有一个可用的通用图表。顶点的类型当前定义为：

typedef struct vertex {
  void *data;
  char *label;
  bool inGraph;
} vertex;

然后可以为任何算法自定义 void 指针，例如 BFS、DFS 等。这是可行的，但我想通过为顶点使用单独的头文件来简化代码，该顶点根据需要指定其类型，并包含在图中。H。像这样的东西：

#ifndef VERTEX_H_INCLUDED
#define VERTEX_H_INCLUDED

#include <stdlib.h>
#include <stdbool.h>

#if defined (GRAPH_VERTEX1)
typedef struct vertex {
  struct vertex *parent;      
  char *label;        
  bool inGraph;       
} vertex;

#elif defined (GRAPH_VERTEX2)
typedef struct vertex {
  size_t dist;    
  char *label;        
  bool inGraph;       
} vertex;

#else  // default
typedef struct vertex {   
  char *label;        
  bool inGraph;       
} vertex;

#endif

#endif

然而，这不起作用。未选择和分配正确的顶点类型。

我做了一个例子来重现这个问题。

main.c

#include <stdio.h>

#define GRAPH_VERTEX1

#include "graph.h"

int main() {
  vertex *v = createVertex("test");
  v->inGraph = true;
  vertex *parent = createVertex("parent");

  printf("Vertex: %s\n", v->label);
  printf("Parent: %s\n", parent->label);
  printf("In graph: %d\n", parent->inGraph);

  freeVertex(v);
  freeVertex(parent);
  return 0;
}

图.h

#ifndef GRAPH_H_INCLUDED
#define GRAPH_H_INCLUDED

#include <stdlib.h>

#include "vertex.h"


vertex *createVertex(char *label);

void freeVertex(vertex *v);


#endif

图.c

#include "graph.h"
#include <string.h>

vertex *createVertex(char *label) {
  vertex *v = calloc(1, sizeof(vertex));
  v->label = calloc(strlen(label) + 1, sizeof(char));
  v->inGraph = false;
  strcpy(v->label, label);
  return v;
}

void freeVertex(vertex *v) {
  free(v->label);
  free(v);
}

如果我在 vertex.h 中放置单个定义，则该示例可以正常工作。但是，如果我尝试使用 if 指令，我会收到以下错误：

==986== Memcheck, a memory error detector
==986== Copyright (C) 2002-2017, and GNU GPL'd, by Julian Seward et al.
==986== Using Valgrind-3.18.1 and LibVEX; rerun with -h for copyright info
==986== Command: ./a.out
==986==
==986== Invalid write of size 1
==986==    at 0x1090FD: main (in /mnt/d/Dropbox/Programs/pubgithub/CLRS/datastructures/graphs/dgraph/a.out)
==986==  Address 0x4a8e050 is 0 bytes after a block of size 16 alloc'd
==986==    at 0x484DA83: calloc (in /usr/libexec/valgrind/vgpreload_memcheck-amd64-linux.so)
==986==    by 0x109279: createVertex (in /mnt/d/Dropbox/Programs/pubgithub/CLRS/datastructures/graphs/dgraph/a.out)       
==986==    by 0x1090F5: main (in /mnt/d/Dropbox/Programs/pubgithub/CLRS/datastructures/graphs/dgraph/a.out)
==986==
==986== Invalid read of size 1
==986==    at 0x10913A: main (in /mnt/d/Dropbox/Programs/pubgithub/CLRS/datastructures/graphs/dgraph/a.out)
==986==  Address 0x4a8e0f0 is 0 bytes after a block of size 16 alloc'd
==986==    at 0x484DA83: calloc (in /usr/libexec/valgrind/vgpreload_memcheck-amd64-linux.so)
==986==    by 0x109279: createVertex (in /mnt/d/Dropbox/Programs/pubgithub/CLRS/datastructures/graphs/dgraph/a.out)       
==986==    by 0x109108: main (in /mnt/d/Dropbox/Programs/pubgithub/CLRS/datastructures/graphs/dgraph/a.out)
==986==
Vertex: (null)
Parent: (null)
In graph: 0
==986== 
==986== HEAP SUMMARY:
==986==     in use at exit: 0 bytes in 0 blocks
==986==   total heap usage: 5 allocs, 5 frees, 4,140 bytes allocated
==986==
==986== All heap blocks were freed -- no leaks are possible
==986==
==986== ERROR SUMMARY: 2 errors from 2 contexts (suppressed: 0 from 0)
==986==
==986== 1 errors in context 1 of 2:
==986== Invalid read of size 1
==986==    at 0x10913A: main (in /mnt/d/Dropbox/Programs/pubgithub/CLRS/datastructures/graphs/dgraph/a.out)
==986==  Address 0x4a8e0f0 is 0 bytes after a block of size 16 alloc'd
==986==    at 0x484DA83: calloc (in /usr/libexec/valgrind/vgpreload_memcheck-amd64-linux.so)
==986==    by 0x109279: createVertex (in /mnt/d/Dropbox/Programs/pubgithub/CLRS/datastructures/graphs/dgraph/a.out)       
==986==    by 0x109108: main (in /mnt/d/Dropbox/Programs/pubgithub/CLRS/datastructures/graphs/dgraph/a.out)
==986==
==986==
==986== 1 errors in context 2 of 2:
==986== Invalid write of size 1
==986==    at 0x1090FD: main (in /mnt/d/Dropbox/Programs/pubgithub/CLRS/datastructures/graphs/dgraph/a.out)
==986==  Address 0x4a8e050 is 0 bytes after a block of size 16 alloc'd
==986==    at 0x484DA83: calloc (in /usr/libexec/valgrind/vgpreload_memcheck-amd64-linux.so)
==986==    by 0x109279: createVertex (in /mnt/d/Dropbox/Programs/pubgithub/CLRS/datastructures/graphs/dgraph/a.out)       
==986==    by 0x1090F5: main (in /mnt/d/Dropbox/Programs/pubgithub/CLRS/datastructures/graphs/dgraph/a.out)
==986==
==986== ERROR SUMMARY: 2 errors from 2 contexts (suppressed: 0 from 0)

Answer 1

graph.c

 需要具有与 

#define GRAPH_VERTEX1

 中相同的 

main.c

 - 否则使用的翻译将获得默认的 

vertex

 定义（因为 

GRAPH_VERTEX1

 和 

GRAPH_VERTEX2

 都不会被定义）。

您可以将

#define GRAPH_VERTEX1

 放入单独的头文件中，并从 

main.c

 和 

graph.c

 中包含该头文件：

#ifndef SOMENAME_H
#define SOMENAME_H

#define GRAPH_VERTEX1
#include "graph.h"

#endif

...或者只是将其放在

graph.h

的顶部。