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我在 vs2010 中创建了 win32 控制台应用程序（没有选择预编译头选项）。我在下面插入了代码。但 *.obj 链接失败。您能否向我提供有关该错误的更多信息。我搜索了MSDN，但仍然无法理解。

#include <stdio.h>
#include "zlib.h"

// Demonstration of zlib utility functions

unsigned long file_size(char *filename)
{
   FILE *pFile = fopen(filename, "rb");
    fseek (pFile, 0, SEEK_END);
    unsigned long size = ftell(pFile);
    fclose (pFile);
    return size;
 }

 int decompress_one_file(char *infilename, char *outfilename)
 {
    gzFile infile = gzopen(infilename, "rb");
    FILE *outfile = fopen(outfilename, "wb");
    if (!infile || !outfile) return -1;

    char buffer[128];
    int num_read = 0;
    while ((num_read = gzread(infile, buffer, sizeof(buffer))) > 0) {
       fwrite(buffer, 1, num_read, outfile);
       }

    gzclose(infile);
    fclose(outfile);
 }

 int compress_one_file(char *infilename, char *outfilename)
 {
    FILE *infile = fopen(infilename, "rb");
    gzFile outfile = gzopen(outfilename, "wb");
    if (!infile || !outfile) return -1;

    char inbuffer[128];
   int num_read = 0;
    unsigned long total_read = 0, total_wrote = 0;
    while ((num_read = fread(inbuffer, 1, sizeof(inbuffer), infile)) > 0) {
       total_read += num_read;
       gzwrite(outfile, inbuffer, num_read);
    }
    fclose(infile);
    gzclose(outfile);

    printf("Read %ld bytes, Wrote %ld bytes, Compression factor %4.2f%%\n",
       total_read, file_size(outfilename),
       (1.0-file_size(outfilename)*1.0/total_read)*100.0);
 }        
 int main(int argc, char **argv)
 {
    compress_one_file(argv[1],argv[2]);
    decompress_one_file(argv[2],argv[3]);}

输出：

1>------ Build started: Project: zlibApp, Configuration: Debug Win32 ------
1>  zlibApp.cpp
1>d:\learning\cpp\cppvs2010\zlibapp\zlibapp\zlibapp.cpp(15): warning C4996: 'fopen': This function or variable may be unsafe. Consider using fopen_s instead. To disable deprecation, use _CRT_SECURE_NO_WARNINGS. See online help for details.
1>          c:\program files\microsoft visual studio 10.0\vc\include\stdio.h(234) : see declaration of 'fopen'
1>d:\learning\cpp\cppvs2010\zlibapp\zlibapp\zlibapp.cpp(25): warning C4996: 'fopen': This function or variable may be unsafe. Consider using fopen_s instead. To disable deprecation, use _CRT_SECURE_NO_WARNINGS. See online help for details.
1>          c:\program files\microsoft visual studio 10.0\vc\include\stdio.h(234) : see declaration of 'fopen'
1>d:\learning\cpp\cppvs2010\zlibapp\zlibapp\zlibapp.cpp(40): warning C4996: 'fopen': This function or variable may be unsafe. Consider using fopen_s instead. To disable deprecation, use _CRT_SECURE_NO_WARNINGS. See online help for details.
1>          c:\program files\microsoft visual studio 10.0\vc\include\stdio.h(234) : see declaration of 'fopen'
1>d:\learning\cpp\cppvs2010\zlibapp\zlibapp\zlibapp.cpp(36): warning C4715: 'decompress_one_file' : not all control paths return a value
1>d:\learning\cpp\cppvs2010\zlibapp\zlibapp\zlibapp.cpp(57): warning C4715: 'compress_one_file' : not all control paths return a value
1>zlibApp.obj : error LNK2019: unresolved external symbol _gzclose referenced in function "int __cdecl decompress_one_file(char *,char *)" (?decompress_one_file@@YAHPAD0@Z)
1>zlibApp.obj : error LNK2019: unresolved external symbol _gzread referenced in function "int __cdecl decompress_one_file(char *,char *)" (?decompress_one_file@@YAHPAD0@Z)
1>zlibApp.obj : error LNK2019: unresolved external symbol _gzopen referenced in function "int __cdecl decompress_one_file(char *,char *)" (?decompress_one_file@@YAHPAD0@Z)
1>zlibApp.obj : error LNK2019: unresolved external symbol _gzwrite referenced in function "int __cdecl compress_one_file(char *,char *)" (?compress_one_file@@YAHPAD0@Z)
1>D:\learning\cpp\cppVS2010\zlibApp\Debug\zlibApp.exe : fatal error LNK1120: 4 unresolved externals
========== Build: 0 succeeded, 1 failed, 0 up-to-date, 0 skipped ==========
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1 回答 1

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啊，请原谅我的提问，但您实际上是在为 zlib 链接库或目标文件吗（可能zlib1.dll如果您使用的是最新版本）？

该错误通常是由于您缺少包含代码的实际库这一事实引起的。包含头文件的事实让编译器知道这些函数存在，但是除非您将库与主代码一起链接，否则链接器将无法找到它们。

你的其他问题是次要的。忽略那些建议您使用所谓的“安全”功能的人。这只是微软试图锁定一些供应商，对想要按照标准编写代码的程序员造成伤害。您可以通过添加关闭这些警告

#define _CRT_SECURE_NO_DEPRECATE

到源文件的顶部。

“并非所有控制路径”警告是因为您指定两个函数返回一个，int但实际上并没有返回一个。现在只需将它们更改为返回 a void，您可以稍后添加错误检查。

于 2010-05-12T07:31:14.557 回答