Question

我在vs2010中创建了win32控制台应用程序（没有选择预编译头文件的选项）。我在下面插入了代码。但* .obj链接失败。你能否提供有关错误的更多信息。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 ==========

Answer 1

啊，请原谅我，但你是否实际链接了zlib的库或目标文件（如果你使用的是最新版本，可能是zlib1.dll）？

该错误通常是由于您错过了包含其中代码的实际库。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链接在一起，否则链接器将无法找到它们。

你的其他问题很小。忽略那些暗示你使用所谓的“安全”功能的人。这只是微软试图锁定供应商并对想要编写标准代码的程序员造成伤害。您可以通过添加

来关闭这些警告

#define _CRT_SECURE_NO_DEPRECATE

到源文件的顶部。

“并非所有控制路径”警告是因为您指定了两个函数来返回int，但实际上并未返回一个。现在只需更改那些以返回void，您可以稍后添加错误检查。

错误LNK2019用于ZLib示例代码编译

1 个答案: