Bus Error (Core Dumped) with sscanf

I have a C program with the following structs and main function.

Code:

---


struct Block {
  int tag;
  int valid;
};


struct Set {
    struct Block *blocks;
    int mru;
};
 
struct Cache {
    int BlockSize, NumSets, NumWays; // block size, number of sets, associativity
    struct Set *sets;

};
 

struct Cache *cache_init(const char *name, const char *config)
{

    struct Cache *c = (struct cache_t *)malloc(sizeof(struct cache_t));

    if (sscanf(config, "%u:%u:%u", &c->bsize, &c->nsets, &c->nways) != 3) {
        fprintf(stderr, "%s configuration: none|<bsize>:<nsets>:<nways>\n", name);
        exit(-1);  }
    else if (c->BlockSize < 1 || !IS_POWEROF2(c->BlockSize)) {
        fprintf(stderr, "%s bsize (%u) must be positive and a power of 2\n",name,

c->BlockSize);        exit(-1);
    }
 
    else if (c->NumSets < 1 || !IS_POWEROF2(c->NumSets)) {
        fprintf(stderr, "%s sets (%u) must be positive and a power of 2\n", name,

c->NumSets);             
    exit(-1);
    }
 
    else if (c->NumWays < 1) {
        fprintf(stderr, "%s ways (%u) must be positive\n", c->Numways);
        exit(-1);
    }
 
    return c;

}

int main(int argc, char **argv) { 
  char buf[256];
  FILE *f = fopen("house.trace", "r");

  struct Cache *InstructionCache = NULL;
  struct Cache *DataCache = NULL;
 

  // check if program was called with the correct number of arguments
  // if not, print usage message and exit

  if (argc != 3) {
    fprintf(stderr, "usage: MyProgram none|<i-arg1>:<i-arg2>:<i-arg3>

none|i|<d-arg1>:<d-arg2>:<d-arg3>\n");
    exit(-1);
    }
 
  printf("argv[0] = %s\n", argv[0]) ;
  printf("argv[1] = %s\n", argv[1]) ;
  printf("argv[2] = %s\n", argv[2]) ;
 
  printf("strcmp(argv[1], none) = %d", strcmp(argv[1], "none")) ;

   
  if (strcmp(argv[1], "none") == 0) {
    icache = cache_init("icache", argv[1]);
  }
 
  else {

    InstructionCache = cache_init("icache", argv[1]) ;
    DataCache = cache_init("dcache", argv[2]) ;
     
  }

  /* More code */

}

---

The program gives a Bus error (core dumped) at the line:

if (sscanf(config, "%u:%u:%u", &c->bsize, &c->nsets, &c->nways) != 3)

Does anyone know how to fix this?

I thank the solver in advance.

But but but ... you don't have a bsize, nsets, or nways element in your struct. Also you have a lot of Cache's and some cache_t's. If somehow that's all fixed in your actual code (which I suppose it must be if it compiles?) then who knows.

Code:

---

struct Cache *c = (struct cache_t *)malloc(sizeof(struct cache_t));

---

do not cast malloc - read FAQ

use

Code:

---

struct Cache *c = malloc(sizeof(*c));

---

to avoid mix-up of types

You need to post the actual code which compiles, runs and crashes.

Not some cut-down code, or worse, something recited from memory.

Cut down code is fine, as long as it can be immediately tested and really demonstrates the problem.

Sorry, the correct code should be:

<code>


Sorry, the code should be:

Code:

---



struct Block {
  int tag;
  int valid;
};


struct Set {
    struct Block *blocks;
    int mru;
};
 
struct Cache {
    int BlockSize, NumSets, NumWays; // block size, number of sets, associativity
    struct Set *sets;

};
 

struct Cache *cache_init(const char *name, const char *config)
{

    struct Cache *c = (struct Cache*)malloc(sizeof(struct Cache));

    if (sscanf(config, "%u:%u:%u", &c->BlockSize, &c->NumSets, &c->NumWays) != 3) {
        fprintf(stderr, "%s configuration: none|<BlockSize>:<NumSets>:<NumWays>\n", name);
        exit(-1);  }
    else if (c->BlockSize < 1 || !IS_POWEROF2(c->BlockSize)) {
        fprintf(stderr, "%s BlockSize (%u) must be positive and a power of 2\n",name,

c->BlockSize);        exit(-1);
    }
 
    else if (c->NumSets < 1 || !IS_POWEROF2(c->NumSets)) {
        fprintf(stderr, "%s sets (%u) must be positive and a power of 2\n", name,

c->NumSets);             
    exit(-1);
    }
 
    else if (c->NumWays < 1) {
        fprintf(stderr, "%s ways (%u) must be positive\n", c->Numways);
        exit(-1);
    }
 
    return c;

}

int main(int argc, char **argv) { 
  char buf[256];
  FILE *f = fopen("house.trace", "r");

  struct Cache *InstructionCache = NULL;
  struct Cache *DataCache = NULL;
 

  // check if program was called with the correct number of arguments
  // if not, print usage message and exit

  if (argc != 3) {
    fprintf(stderr, "usage: MyProgram none|<i-arg1>:<i-arg2>:<i-arg3>

none|i|<d-arg1>:<d-arg2>:<d-arg3>\n");
    exit(-1);
    }
 
  printf("argv[0] = %s\n", argv[0]) ;
  printf("argv[1] = %s\n", argv[1]) ;
  printf("argv[2] = %s\n", argv[2]) ;
 
  printf("strcmp(argv[1], none) = %d", strcmp(argv[1], "none")) ;

   
  if (strcmp(argv[1], "none") == 0) {
    icache = cache_init("icache", argv[1]);
  }
 
  else {

    InstructionCache = cache_init("icache", argv[1]) ;
    DataCache = cache_init("dcache", argv[2]) ;
     
  }

  /* More code */

}

---

But still giving the afore-mentioned Bus-Error.

I have tried vart's suggestion to not cast malloc , but I still get the Bus-Error.

Here is the gdb output.


run 4:16:2 4:16:2
Starting program: cache 4:16:2 4:16:2
Here

After 3 arguments check.

argc = 3

argv[0] = cache
argv[1] = 4:16:2
argv[2] = 4:16:2

Program received signal SIGSEGV, Segmentation fault.
0xff311678 in number () from /usr/lib/libc.so.1

You need to run a backtrace (bt) to see where in your code you actually are/were to do the debugging.

you are using %u format for reading ints - use %d,
you should check return values of malloc before using it

add printfs traces to see where your program crashes... Do you use somewhere not initialized pointer Sets?

Apart from using %d instead of %u, it would probably help if you had an #include'd stdio.h, string.h, and stdlib.h in your source file. Without them, the compiler is making particular assumptions about the signatures of various functions which may or may not be valid.

On a quick look, the error is occurring just after printing out argv[0] - argv[2]. The output from this line

Code:

---

printf("strcmp(argv[1], none) = %d", strcmp(argv[1], "none")) ;

---

is not evident. That suggests (unless stdout is being buffered) the error is occurring earlier than the sccanf() call.

Methinks! grumpy is on the right track so post the command used to invoke the program.