I'm Tryng to write a code that have to expand the memory of a malloc array of 1 for some cicles of a loop (i need to store the zeros of a function). but after compiling this error occurs:
realloc(): invalid next size
Aborted (core dumped)
have someone an idea of the reasons of this error?
here's the the code:
#include <stdio.h>
#include <stdlib.h>
#include <math.h>
#define ARGMAX 5
#define ARGUMENTS_ERROR -3
#define REALLOC_FAILURE -2
typedef struct{
double x;
double y;
}point;
point Func(point p,double dt);
double Tzero(double x1,double x2,double dt,int i);
//START
int main(int argc,char* argv[]){
int n,i,nzeri=0;
point p,pp;
double *tzeri, *temp;
tzeri=(double *)malloc(0*sizeof(double));
pp.x=atof(argv[1]);
pp.y=atof(argv[2]);
double dt=atof(argv[3]);
double tmax=atof(argv[4]);
n=(int)tmax/dt;
for(i=0;i<n;i++){
p=Func(pp,dt);
printf("%lf %lf\n",dt*(i+1),p.x);
if(pp.x*p.x<=0.){
nzeri++;
temp=(double *)realloc(tzeri,nzeri*sizeof(double));
if(temp==NULL){
printf("--------ERROR-------\nrealloc failed\n");
exit(REALLOC_FAILURE);
}
tzeri[nzeri-1]=Tzero(pp.x,p.x,dt,i);
printf("----------\n%d %lf\n----------\n",nzeri,tzeri[nzeri-1]);
}
pp.x=p.x;
pp.y=p.y;
}
}//END
point Func(point p,double dt){
point p2;
p2.x=p.x-0.1;
if(p2.x<-3)p2.x=3.;
return p2;
}
double Tzero(double x1,double x2,double dt,int i){
double d,t;
d=x1*dt/(x1-x2);
t=dt*i+d;
return t;
}
I expect the size of tzeri to grow by one 'cell' (one sizeof(double)) in a way like nzeri, but it seems to work just until the fifth reallocation, so it can't be a syntax error.
hope for news soon, thanks
----UPDATES----
i build the program with the debugging parameters -g -fsanitize=address and i got this:
==6465==ERROR: AddressSanitizer: heap-use-after-free on address 0x602000000010 at pc 0x55fe8cdcc642 bp 0x7fff53fd3280 sp 0x7fff53fd3270
WRITE of size 8 at 0x602000000010 thread T0
#0 0x55fe8cdcc641 in main /home/gerry/Desktop/FisComp/2088811/error.c:42
#1 0x7ff3aaa29d8f (/lib/x86_64-linux-gnu/libc.so.6+0x29d8f)
#2 0x7ff3aaa29e3f in __libc_start_main (/lib/x86_64-linux-gnu/libc.so.6+0x29e3f)
#3 0x55fe8cdcc244 in _start (/home/gerry/Desktop/FisComp/2088811/a.x+0x1244)
0x602000000011 is located 0 bytes to the right of 1-byte region [0x602000000010,0x602000000011)
freed by thread T0 here:
#0 0x7ff3aaeb4c38 in __interceptor_realloc ../../../../src/libsanitizer/asan/asan_malloc_linux.cpp:164
#1 0x55fe8cdcc5a6 in main /home/gerry/Desktop/FisComp/2088811/error.c:37
#2 0x7ff3aaa29d8f (/lib/x86_64-linux-gnu/libc.so.6+0x29d8f)
previously allocated by thread T0 here:
#0 0x7ff3aaeb4887 in __interceptor_malloc ../../../../src/libsanitizer/asan/asan_malloc_linux.cpp:145
#1 0x55fe8cdcc3b6 in main /home/gerry/Desktop/FisComp/2088811/error.c:25
#2 0x7ff3aaa29d8f (/lib/x86_64-linux-gnu/libc.so.6+0x29d8f)
SUMMARY: AddressSanitizer: heap-use-after-free /home/gerry/Desktop/FisComp/2088811/error.c:42 in main
Shadow bytes around the buggy address:
0x0c047fff7fb0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
0x0c047fff7fc0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
0x0c047fff7fd0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
0x0c047fff7fe0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
0x0c047fff7ff0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
=>0x0c047fff8000: fa fa[fd]fa fa fa 00 fa fa fa fa fa fa fa fa fa
0x0c047fff8010: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
0x0c047fff8020: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
0x0c047fff8030: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
0x0c047fff8040: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
0x0c047fff8050: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
Shadow byte legend (one shadow byte represents 8 application bytes):
Addressable: 00
Partially addressable: 01 02 03 04 05 06 07
Heap left redzone: fa
Freed heap region: fd
Stack left redzone: f1
Stack mid redzone: f2
Stack right redzone: f3
Stack after return: f5
Stack use after scope: f8
Global redzone: f9
Global init order: f6
Poisoned by user: f7
Container overflow: fc
Array cookie: ac
Intra object redzone: bb
ASan internal: fe
Left alloca redzone: ca
Right alloca redzone: cb
Shadow gap: cc
==6465==ABORTING
Someone can find the error?
Your code never assigns a new value to tzeri
. It first sets tzeri
with tzeri=(double *)malloc(0*sizeof(double));
. Later, it allocates new space with temp=(double *)realloc(tzeri,nzeri*sizeof(double));
, but it never assigns that value to tzeri
. After checking that temp
is not null, you need tzeri = temp;
.