从“char *”赋值给“char”可以从指针生成整数，而不会在 C 中出现转换错误

Question

我正在构建一个 C 工具，它将搜索 XML 文件中的所有属性，并使用curl 来抓取它们并检查它们是否返回 404 错误或者它们是否正在工作。

到目前为止，我的代码的所有模块都运行良好，除了当我尝试将获取的 URL 列表存储在 urlStack 变量中时，我收到此警告：

crawler.c: In function ‘locXMl’:
crawler.c:119:34: warning: assignment to ‘char’ from ‘char *’ makes integer from pointer without a cast [-Wint-conversion]
  119 |             urlStack[stackIndex] = regSearch("<loc>[^<]*<\\/loc>",fileData);

当我运行编译的文件时，出现分段错误错误。

这是代码：

#include <stdio.h>
#include <curl/curl.h>
#include <string.h>
#include <regex.h>


int statusCode(char *addr);
char* regSearch(char* regPattern, char* hayStack);
char locXMl(char* fileName, char* urlStack );

int main(int argc, char *argv[]) {
    char* urlStack[] = {};
    
    //checking if the file name is specified
    if(argc < 2){
        printf("\nMissing file name.\n");
        return 1;
    } //else continue


    //checking if the file exsits
    FILE *file;
    if((file = fopen(argv[1],"r")) == NULL )
        {
            printf("\nSpecified file does not exist\n");
            printf("\n%s\n",argv[1]);
            return 1;
        }

    //build the list of URLs in urlStack
    locXMl(argv[1],*urlStack);


}



int statusCode(char *addr){

    CURL *curl;
    CURLcode res;
    long response_code;

    // Initialize curl
    curl_global_init(CURL_GLOBAL_DEFAULT);

    // Create a curl handle
    curl = curl_easy_init();
    if (curl) {
        curl_easy_setopt(curl, CURLOPT_URL, addr);
        curl_easy_setopt(curl, CURLOPT_NOBODY, 1);

        res = curl_easy_perform(curl);
        if(res == CURLE_OK) {

            curl_easy_getinfo(curl, CURLINFO_RESPONSE_CODE, &response_code);
        }
        curl_easy_cleanup(curl);
    }

    // Cleanup global curl resources
    curl_global_cleanup();
    return  response_code;

}



/* Use regex to get matching url from the XML */

char* regSearch(char* regPattern, char* hayStack) {
    regex_t regex;
    int reti;
    char *string = hayStack;
    char *pattern = regPattern;
    regmatch_t match;

    // Compile the regular expression
    reti = regcomp(&regex, pattern, 0);
    if (reti) {
        fprintf(stderr, "Could not compile regex\n");
     
    }

    // Execute the regular expression
    reti = regexec(&regex, string, 1, &match, 0);
    //print the found match
    if (!reti) {

        return string;

    } else if (reti == REG_NOMATCH) {
            // do something if the match is not found
    } else {
        fprintf(stderr, "Regex execution failed\n");
        
    }

    // Free the compiled regular expression
    regfree(&regex);

   
}


/* get all the URLs from within the loc element in XML */
char locXMl(char* fileName, char* urlStack ){

    FILE *fptr;
    fptr = fopen(fileName,"r");  
    char fileData[100];

    int stackIndex = 0;

    while(fgets(fileData, 100, fptr)) {

        if(regSearch("<loc>[^<]*<\\/loc>",fileData)){

            urlStack[stackIndex] = regSearch("<loc>[^<]*<\\/loc>",fileData);
            stackIndex++;
           //printf("%s\n",  regSearch("<loc>[^<]*<\\/loc>",fileData));
        }

    }
   
}

我尝试更改 urlStack 变量的声明方式，但问题仍然存在。期望将所有 URL 作为数组放入该变量中。

Answer 1

您需要在声明中添加一个额外的星号：

    char locXMl(char* fileName, char** urlStack );

并且调用时没有星号：

    locXMl(argv[1],urlStack);

当然，你必须为

urlStack

中的所有指针分配空间。

您还会收到有关不返回值的非 void 函数以及将字符串常量作为非常量 char* 传递的警告。但你没有问过他们。

Answer 2

我根据@SupportUkraine提供的答案修改了代码如下，这解决了我在这里提到的具体问题：

#include <stdio.h>
#include <curl/curl.h>
#include <string.h>
#include <regex.h>
#include <stdlib.h>


int statusCode(char *addr);
char* regSearch(char* regPattern, char* hayStack);
char** locXMl(char* fileName, char** urlStack );

int main(int argc, char *argv[]) {
    char* urlStack[1000];
    
    //checking if the file name is specified
    if(argc < 2){
        printf("\nMissing file name.\n");
        return 1;
    } //else continue


    //checking if the file exsits
    FILE *file;
    if((file = fopen(argv[1],"r")) == NULL )
        {
            printf("\nSpecified file does not exist\n");
            printf("\n%s\n",argv[1]);
            return 1;
        }
    fclose(file);    

    //build the list of URLs in urlStack
   char** data =  locXMl(argv[1],urlStack);
    
    printf("%s",urlStack[10]);
    


}



int statusCode(char *addr){

    CURL *curl;
    CURLcode res;
    long response_code;

    // Initialize curl
    curl_global_init(CURL_GLOBAL_DEFAULT);

    // Create a curl handle
    curl = curl_easy_init();
    if (curl) {
        curl_easy_setopt(curl, CURLOPT_URL, addr);
        curl_easy_setopt(curl, CURLOPT_NOBODY, 1);

        res = curl_easy_perform(curl);
        if(res == CURLE_OK) {

            curl_easy_getinfo(curl, CURLINFO_RESPONSE_CODE, &response_code);
        }
        curl_easy_cleanup(curl);
    }

    // Cleanup global curl resources
    curl_global_cleanup();
    return  response_code;

}



/* Use regex to get matching url from the XML */

char* regSearch(char* regPattern, char* hayStack) {
    regex_t regex;
    int reti;
    char *string = hayStack;
    char *pattern = regPattern;
    regmatch_t match;

    // Compile the regular expression
    reti = regcomp(&regex, pattern, 0);
    if (reti) {
        fprintf(stderr, "Could not compile regex\n");
     
    }

    // Execute the regular expression
    reti = regexec(&regex, string, 1, &match, 0);
    //print the found match
    if (!reti) {

        regfree(&regex);
        return string;

    } else if (reti == REG_NOMATCH) {
            // do something if the match is not found
    } else {
        fprintf(stderr, "Regex execution failed\n");
        
    }

    // Free the compiled regular expression
    regfree(&regex);

   
}


/* get all the URLs from within the loc element in XML */
char** locXMl(char* fileName, char** urlStack ){

    FILE *fptr;
    fptr = fopen(fileName,"r");  
    char fileData[100];

    int stackIndex = 0;

    while(fgets(fileData, 100, fptr)) {

        if(regSearch("<loc>[^<]*<\\/loc>",fileData)){

            urlStack[stackIndex] = strcat(regSearch("<loc>[^<]*<\\/loc>",fileData), "");
            //printf("%s\n",urlStack[stackIndex]);
            stackIndex++;
         
        }

    }

    fclose(fptr);
    return urlStack;
   
}