Segmentation Fault with fopen

[macaco]

Hi, I'm getting a segmentation fault on this code when it gets to fopen:

tac.h:

typedef struct
{
    char* ventanaInspeccion;
    char* ventanaMemoria;
    FILE* archivo; 
} TAC;
 
int TAC_Abrir(TAC* tac, char* archMensaje);
 

main.c

TAC tac;
TAC_Abrir(&tac, argv[2]);

tac.c:

int TAC_Abrir(TAC* tac, char* archMensaje){
tac->archivo=fopen(archMensaje,"rt");

This not all the code, but the part with the problem..
As I said, when it gets to fopen(), a segmentation fault occurs. archMensaje's content is fine and file exists.

Why could this be happening?

Many Thanks

[pootle]

Did you check the tac pointer? When you dereference it to put the result of fopen into archivo is it valid? How is it allocated?

Regards

[arnaudk]

The only potential error I can see is the mode of fopen. I'm not familiar with "t" perhaps you mean "r+"? If "t" is valid for the library you're using then the error is elsewhere in your code.

[macaco]

Did you check the tac pointer? When you dereference it to put the result of fopen into archivo is it valid? How is it allocated?

Regards

It is allocated when program starts. As I am declaring tac as struct, not as a pointer to struct.

The only potential error I can see is the mode of fopen. I'm not familiar with "t" perhaps you mean "r+"? If "t" is valid for the library you're using then the error is elsewhere in your code.

't' is used to make it clear that it'll be a text file and not a binary 'b'. However, I did try with r, without success.
Debugger breaks on that line, how could the problem be elsewhere?

Many Thanks both!

[donbock]

Hi, I'm getting a segmentation fault on this code when it gets to fopen:

tac->archivo=fopen(archMensaje,"rt");

Do you know if the fault occurs during the execution of fopen() or when you write into the structure? You might introduce a temporary variable just while debugging this in order to clarify where the problem is. This also gives you chance to see if fopen() is returning NULL.

FILE *theFile;
theFile = fopen(archMensaje,"rt");
tac->archivo = theFile;

Cheers,
donbock

[pootle]

Do you know if the fault occurs during the execution of fopen() or when you write into the structure? You might introduce a temporary variable just while debugging this in order to clarify where the problem is. This also gives you chance to see if fopen() is returning NULL.

FILE *theFile;
theFile = fopen(archMensaje,"rt");
tac->archivo = theFile;

Cheers,
donbock

And also...
You said that archMensaje is correct - but are you sure it is properly alllocated/null terminated? Passing a rubbish filename pointer would cause a segfault... Just for testing, try replacing it with a literal string...

[pootle]

For fun (I've nothing better to do...)
I tried taking your code and running it on my Linux box...

#include <stdio.h>
 
typedef struct
{
    char* ventanaInspeccion;
    char* ventanaMemoria;
    FILE* archivo; 
} TAC;
 
int TAC_Abrir(TAC* tac, char* archMensaje) {
    tac->archivo=fopen(archMensaje,"rt");
    if (tac->archivo == NULL) {
       printf("NULL\n");
    }
    else {
       printf("not NULL\n");
    }
}
 
int main(int argc, char** argv) {
   TAC tac;
   TAC_Abrir(&tac, argv[2]);
 
   return 0;
}

This code, when runs without any segmentation fault...
I just passed two arguments on the command line and if the file exists, it prints "not NULL", if it does not, it prints "NULL".

Could you try compiling and running this code to see if you still get a segfault?

[bgross]

I have the same issue. It seems the problem is that MinGW's fopen function does not work properly. I've seen this time and time again in my own code.

I got the same results as pootle, my code would run perfectly fine (or at least fopen ;) ) using any other compiler.