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I used the same code for both but I get a segmentation fault in Debian. Why is the reason for this error?

Note: I know code does not make sense, it is school homework. Error images are added below. I investigate similar topics but I did not find an error solution.

Error image in Debian

Works fine for windows

Here is the code:

#include <stdio.h>
#include <string.h>

struct record {
    char name[64]; //utf16
    char surname[32]; //utf8
    char gender[1];
    char email[32];
    char phone_number[16];
    char address[32];
    char level_of_education[8];
    unsigned int income_level; // given little-endian
    unsigned int expenditure; // given big-endian
    char currency_unit[16];
    char currentMood[32];
    float height;
    unsigned int weight;

};

struct tag {
    char name[5];
    char surname[8];
    char gender[7];
    char email[10];
    char phone_number[13];
    char address[8];
    char level_of_education[19];
    char income_level[13];
    char expenditure[12];
    char currency_unit[14];
    char currentMood[12];
    char height[7];
    char weight[7];

};

/*
 * Converts big endian to little or little endian to big endian
 */
unsigned int endian_swap(unsigned int x)
{
    x = (x>>24) | 
        ((x<<8) & 0x00FF0000) |
        ((x>>8) & 0x0000FF00) |
        (x<<24);
        
    return x;
}

/*
 * Find uncorrect tag headers and fixed 
 */
struct tag rearrange_tag_names(struct tag t){
    struct tag *tagPtr;
    tagPtr = &t;
    // Check name header
    if(strcmp(t.name,"name") != 0) {
        strncpy(tagPtr->name,"name",5);
    }
     // Check surname header
    if(strcmp(t.surname,"surname") != 0) {
        strncpy(tagPtr->surname,"surname",8);
        
    }
     // Check gender header
    if(strcmp(t.gender,"gender") != 0) {
        strncpy(tagPtr->gender,"gender",7);
    }
    // Check email header
    if(strcmp(t.email,"email") != 0) {
        strncpy(tagPtr->email,"email",10);
    }
    // Check phone_number header
    if(strcmp(t.phone_number,"phone_number") != 0) {
        strncpy(tagPtr->phone_number,"phone_number",13);        
    }
    // Check address header
    if(strcmp(t.address,"address") != 0) {
        strncpy(tagPtr->address,"address",8);
    }
    // Check level_of_education header
    if(strcmp(t.level_of_education,"level_of_education") != 0) {
        strncpy(tagPtr->level_of_education,"level_of_education",20);
    }
    // Check income_level header
    if(strcmp(t.income_level,"income_level") != 0) {
        strncpy(tagPtr->income_level,"income_level",14);        
    }
    // Check expenditure header
    if(strcmp(t.expenditure,"expenditure") != 0) {
        strncpy(tagPtr->expenditure,"expenditure",12);
    }
    // Check currency_unit header
    if(strcmp(t.currency_unit,"currency_unit") != 0) {
        strncpy(tagPtr->currency_unit,"currency_unit",14);
    }
    // Check currentMood header
    if(strcmp(t.currentMood,"currentMood") != 0) {
        strncpy(tagPtr->currentMood,"currentMood",12);
    }
    // Check height header
    if(strcmp(t.height,"height") != 0) {
        strncpy(tagPtr->height,"height",7);
    }
    // Check weight header
    if(strcmp(t.weight,"weight") != 0) {
        strncpy(tagPtr->weight,"weight",7);
    }


    // print to test
    //printf("%s \t %s \t %s \t %s \t %s \t %s \t %s \t %s \t %s \t %s \t %s \t %s",t.name,t.surname,t.gender,t.email,t.phone_number,t.address,t.level_of_education,t.income_level,t.expenditure,t.currency_unit,t.currentMood,t.height,t.weight);
    return t;
}

/*
 * Creates XML from given records
 */
void createXML(struct record* arr,struct tag tag,char *xml_name)
{
    // Create file pointer
    FILE  *fxml;
    //Check if error is occured
    if ((fxml = fopen(xml_name,"wt")) == NULL) {    
        printf("%s","Some error is occured.");
                                          
    }


    fprintf (fxml,"<?xml version=\"1.0\" encoding=\"utf-8\"?>\n");
    fprintf(fxml,"<records>\n");
    int i;

    // Print tag to test
    //printf("%s",tag.email);
    //printf("%s",tag.level_of_education);
    // printf("%s",tag.level_of_education);
    // printf("%s",tag.income_level);
    // printf("%s",tag.expenditure);
    // printf("%s",tag.height);
    // printf("%s",tag.weight);
    
    // Crate xml rows
    for (i = 1; i < 51; i++) {
        
        fprintf(fxml,"   <row id='%d'>\n",i);
        fprintf(fxml,"       <%s>%s</%s>\n",tag.name,arr[i].name,tag.name);
        fprintf(fxml,"       <%s>%s</%s>\n",tag.surname,arr[i].surname,tag.surname);
        fprintf(fxml,"       <%s>%s</%s>\n",tag.gender,arr[i].gender,tag.gender);
        fprintf(fxml,"       <%s>%s</%s>\n",tag.email,arr[i].email,tag.email);
        fprintf(fxml,"       <%s>%s</%s>\n",tag.phone_number,arr[i].phone_number,tag.phone_number);
        fprintf(fxml,"       <%s>%s</%s>\n",tag.address,arr[i].address,tag.address);
        fprintf(fxml,"       <%s>%s</%s>\n",tag.level_of_education,arr[i].level_of_education,tag.level_of_education);
        fprintf(fxml,"       <%s>%d</%s>\n",tag.income_level,arr[i].income_level,tag.income_level);
        fprintf(fxml,"       <%s>%d</%s>\n",tag.expenditure,arr[i].expenditure,tag.expenditure);
        fprintf(fxml,"       <%s>%s</%s>\n",tag.currency_unit,arr[i].currency_unit,tag.currency_unit);
        fprintf(fxml,"       <%s>%s</%s>\n",tag.currentMood,arr[i].currentMood,tag.currentMood);
        fprintf(fxml,"       <%s>%.2f</%s>\n",tag.height,arr[i].height,tag.height);
        fprintf(fxml,"       <%s>%d</%s>\n",tag.weight,arr[i].weight,tag.weight);
        fprintf(fxml,"   </row>\n");
        
    }
    fprintf(fxml,"</records>\n");

    fclose(fxml); //Close file
}


/*
 * Converts bin file to XML
 */
int Bin2XML(char* rafname,char* xml_name)      
{
    // Create necessary variables
    FILE *fraf;
    struct record rec;
    struct tag tag;
    
    struct record arr_rec[50];
    int number_of_record = 51;


    // Encode file in utf-8 format
    if ((fraf = fopen(rafname,"rb, ccs=UTF-8")) == NULL)
        return 0;                                   // failure

    

    fread(&arr_rec, sizeof(struct record), number_of_record, fraf);

    // Read first line into tag and 
    // make necessary convertion and arrangement
    strcpy(tag.name,arr_rec[0].name);
    strcpy(tag.surname,arr_rec[0].surname);
    strcpy(tag.email,arr_rec[0].email);
    strcpy(tag.phone_number,arr_rec[0].phone_number);
    strcpy(tag.address,arr_rec[0].address);
    strcpy(tag.level_of_education,arr_rec[0].level_of_education);
    // convert int income level to string format
    char converted_income_level[10];
    sprintf(converted_income_level,"%d",arr_rec[0].income_level);
    strcpy(tag.income_level,converted_income_level);
    // convert int expenditure  to string format
    char converted_expenditure[10];
    sprintf(converted_expenditure,"%d",arr_rec[0].expenditure);
    strcpy(tag.expenditure,converted_expenditure);
    strcpy(tag.currency_unit,arr_rec[0].currency_unit);
    strcpy(tag.currentMood,arr_rec[0].currentMood);
    // convert float height  to string format
    char buf[10];
    snprintf(buf,5,"%s",arr_rec[0].height);
    
    strcpy(tag.height,buf);
    // convert unsigned weight to string format
    char converted_weight[10];
    sprintf(converted_weight,"%d",arr_rec[0].weight);
    strcpy(tag.weight,converted_weight);
    
    
    tag = rearrange_tag_names(tag);
   
    // Rearrange formats
    int i;
    for(i=1;i<number_of_record;i++){
        arr_rec[i].expenditure = endian_swap(arr_rec[i].expenditure); // Convert big endian to little endian
        // Income level is already little endian but if it was not little endian we can read as little endian
        // with endian_swap function.
        //arr_rec[i].income_level =endian_swap(arr_rec[i].income_level);    
        
        }

    // Create an XML file with readed records
    // First record readed into tag,so we can decrease number of record by one
    createXML(arr_rec,tag,xml_name);

    // close file
    fclose(fraf);
    
    return 1;                                       // success
}



int main(void)
{
  
    if( Bin2XML("records.dat","test.xml") == 1 ){
        printf("Bin file is readed and XML file is created successfully.");
    } else{
        printf("(!) An error occured please check your input file name. (!)");
    }

    return 0;
}

Can someone help me ?

volkanulker
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  • A debugger like gdb can easily show you exactly where the segfault happened without us going through a couple hundred lines of code to try to find the problem. – Kevin May 12 '21 at 21:53
  • I will look at it – volkanulker May 12 '21 at 21:59
  • 1
    *I used the same code for both but I get a segmentation fault in Debian. Why is the reason for this error?* This is typical behavior for code that invokes [undefined behavior](https://en.wikipedia.org/wiki/Undefined_behavior) - it works sometimes or somewhere, but fails under other conditions or when run on another system. I see quite a few `strcpy()` calls that could result in a buffer overflow, and quite a few [`strncpy()` calls that could result in a non-terminated string](https://stackoverflow.com/questions/1453876/why-does-strncpy-not-null-terminate). – Andrew Henle May 12 '21 at 22:00
  • I'll try to get rid of these strcpy() and strncpy(). – volkanulker May 12 '21 at 22:18
  • You have massive code replication. You also have UB: `strncpy(tagPtr->income_level,"income_level",14)` --> `strncpy(tagPtr->income_level,"income_level",13)` (because of: `char income_level[13];`). Your record fields aren't sure whether space for EOS is needed (e.g.) `char hello[5] = "hello";` has no space for `'\0'` but `char hello[6] = "hello";` does. But, your printing code _assumes_ space for EOS because of the `%s` format. Does your file/ondisk data (from `fread`) have space for EOS for _all_ fields? – Craig Estey May 12 '21 at 22:20
  • Please provide your question as a minimum reproducible example... The trick I use is commenting out lines and generalizing code until the problem disappears, then posting the code you had just before the error vanished. – GooseDeveloper May 13 '21 at 00:53

1 Answers1

1

The line

snprintf(buf, 5, "%s", arr_rec[0].height);

is wrong: arr_rec[0].height is a float while the format "%s" specifies a string.

This means that snprintf() access memory in the wild. This cause undefined behavior which can be segmentation fault or access violation under windows depending on what the address is.

By the way, I just compiled your code and the compiler (MSVC) immediately gave the error:

warning C4477: 'snprintf' : format string '%s' requires an argument of type 'char *', but variadic argument 1 has type 'double'
fpiette
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