C program runs in Cygwin but not Linux (Malloc)
- by Shawn
I have a heap allocation error that I cant spot in my code that is picked up on vanguard/gdb on Linux but runs perfectly on a Windows cygwin environment. I understand that Linux could be tighter with its heap allocation than Windows but I would really like to have a response that discovers the issue/possible fix. I'm also aware that I shouldn't typecast malloc in C but it's a force of habit and doesn't change my problem from happening. My program actually compiles without error on both Linux & Windows but when I run it in Linux I get a scary looking result:
malloc.c:3074: sYSMALLOc: Assertion `(old_top == (((mbinptr) (((char *) &((av)-bins[((1) - 1) * 2])) - __builtin_offsetof (struct malloc_chunk, fd)))) && old_size == 0) || ((unsigned long) (old_size) = (unsigned long)((((__builtin_offsetof (struct malloc_chunk, fd_nextsize))+((2 * (sizeof(size_t))) - 1)) & ~((2 * (sizeof(size_t))) - 1))) && ((old_top)-size & 0x1) && ((unsigned long)old_end & pagemask) == 0)' failed.
Aborted
Attached snippet from my code that is being pointed to as the error for review:
/* Main */
int main(int argc, char * argv[]) {
FILE *pFile;
unsigned char *buffer;
long int lSize;
pFile = fopen ( argv[1] , "r" );
if (pFile==NULL) {fputs ("File error on arg[1]",stderr); return 1;}
fseek (pFile , 0 , SEEK_END);
lSize = ftell (pFile);
rewind (pFile);
buffer = (char*) malloc(sizeof(char) * lSize+1);
if (buffer == NULL) {fputs ("Memory error",stderr); return 2;}
bitpair * ppairs = (bitpair *) malloc(sizeof(bitpair) * (lSize+1));
//line 51 below
calcpair(ppairs, (lSize+1));
/* irrelevant stuff */
fclose(pFile);
free(buffer);
free(ppairs);
}
typedef struct {
long unsigned int a; //not actual variable names... Yes I need them to be long unsigned
long unsigned int b;
long unsigned int c;
long unsigned int d;
long unsigned int e;
} bitpair;
void calcpair(bitpair * ppairs, long int bits);
void calcPairs(bitpair * ppairs, long int bits) {
long int i, top, bot, var_1, var_2;
int count = 0;
for(i = 0; i < cs; i++) {
top = 0;
ppairs[top].e = 1;
do {
bot = count;
count++;
} while(ppairs[bot].e != 0);
ppairs[bot].e = 1;
var_1 = bot;
var_2 = top;
calcpair * bp = &ppairs[var_2];
bp->a = var_2;
bp->b = var_1;
bp->c = i;
bp = &ppairs[var_1];
bp->a = var_2;
bp->b = var_1;
bp->c = i;
}
return;
}
gdb reports: free(): invalid pointer: 0x0000000000603290 *
valgrind reports the following message 5 times before exiting due to "VALGRIND INTERNAL ERROR" signal 11 (SIGSEGV):
Invalid read of size 8
==2727== at 0x401043: calcPairs (in /home/user/Documents/5-3/ubuntu test/main)
==2727== by 0x400C9A: main (main.c:51)
==2727== Address 0x5a607a0 is not stack'd, malloc'd or (recently) free'd
