CODEWITHSUNDEEP
cmallocrealloc
cclilshy
cclilshy

Reputation: 49

Why realloc error Thread 1: signal SIGABRT

#include<stdio.h>
#include<stdlib.h>
#include<string.h>
#include<sys/uio.h>
#include<unistd.h>
#include<fcntl.h>
#include<stdarg.h>


void debug(void);
char * string(const char * );
char * strcats(const char * ,const char * );
char * strspe(const char *, ...);
int isDir(const char *);

int main(void){
    debug();
    return 0;
}

void debug(void){
    char * str = "ssssss";
    str = string("abcdef");
    
    char * hello;
    hello = strspe(str,"hello","world","world","world","world","world","world","world","world","world","world","world","world","world","world","world","world","world","world","world","world","world","world","world","world","world","world","world","world","world","world","world","world","world","world","world","world","world","world","world","world","world","world","world","world","world",NULL);
    
    printf("hello: %s   ,Address: %p\n",hello,(char *)hello);
}

char * string(const char * str){
    return strcpy(malloc(strlen(str) * sizeof(char) + sizeof(char)),str);
}

char * strcats(const char * str1,const char * str2){
    int realSize = (int)strlen(str2) * sizeof(char) + (int)strlen(str1) * sizeof(char) + sizeof(char);
    str1 = realloc((char *)str1,realSize);
    strcat((char *)str1,str2);
    return (char *)str1;
}

char * strspe(const char * format, ...)
{
    va_list args;
    const char * argv;
    char * result = string(format);
    //free((char*)format);
    va_start(args, format);
    while((argv = va_arg(args,const char *)) && argv != NULL){
        strcats((char *)result,argv);
    }
    va_end(args);
    return result;
}

int isDir(const char *filename){
    return (access(filename, 0) == 0);
}

Here is a piece of C code ，that sometimes runs, sometimes doesn't run and gives an error Thread 1: signal SIGABRT.

Debug (23028,0x1000ebe00) malloc: *** error for object 0x1007af200: pointer being realloc's d was not allocated Debug (23028,0x1000ebe00) malloc: *** set a breakpoint in malloc_error_break to debug(23028,0x1000ebe00) malloc: *** set a breakpoint in malloc_error_break to debug(23028,0x1000ebe00 (lldb)

And focus the cursor on line 37：

str1 = realloc((char *)str1,realSize);

I can't solve the problem

Upvotes: 1

Views: 130

Answers (1)

Jean-Baptiste Yun&#232;s
Jean-Baptiste Yun&#232;s

Reputation: 36441

Problem is within this loop:

while((argv = va_arg(args,const char *)) && argv != NULL) {
        strcats((char *)result,argv);
}

strcats reallocates the memory associated to result (parameter named str1) but realloc may change the address. You correctly return the new address but never use it, so result never change. Then at a given time, when realloc moves the data to another place, the former is no more valid, at the next loop the bad address is then sent again.

Change to :

while((argv = va_arg(args,const char *)) && argv != NULL){
        result = strcats(result,argv);
}

Upvotes: 0

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