Programming help : STUPID C! HELP! :)

[trilobyte]

*Got it working! Thanks everyone!

 

[bsobel]

Is this your actual code, as I don't see how it can compile. In main you reference input and input2 and then go and use input and input1.
Bill

 

[trilobyte]

Sorry, typo when I was putting it in

I just found out something odd

in my main i have this:
printf("%s\n", books[0]->author.last);
printf("%s\n", books[1]->author.last);

which gives me a segmentation error on the second statement
BUT, if I only have this:
printf("%s\n", books[1]->author.last);

I'm able to acess the last name correctly.

Any ideas as to what causes it to crash when I access books[0] then access books[1]?

 

[singh]

For God's sake, PLEASE host the code somewhere and give us a link! I refuse to look at unformatted code

 

[trilobyte]

Ug, now it seems to give me segmentation errors whenever it wan'ts to (when I try to access the last name)

here's the links:

book.c
bookMain.c

 

[singh]

Originally posted by: trilobyte
Ug, now it seems to give me segmentation errors whenever it wan'ts to (when I try to access the last name)

here's the links:

book.c
bookMain.c

Missing book.h?

 

[trilobyte]

oops sorry

book.h

 

[singh]

Is the code as-given (including the main procedure) supposed to give Segmentation Errors? The code runs fine for me. Maybe your data file is different (post it too )?

By the way, is this for an assignment, or some other reason why you're writing it in C?

 

[trilobyte]

here are the data files:

test.dat
test2.dat

It worked for you? Lemme see what you were using for data. What are you running it in?

Yeah, it's for my C class. I'm not cheating I'm just debugging.

 

[singh]

Originally posted by: trilobyte
here are the data files:

test.dat
test2.dat

It worked for you? Lemme see what you were using for data. What are you running it in?

Yeah, it's for my C class. I'm not cheating I'm just debugging.

I just tested the program with your files. Works fine. I am testing with MSVC++ on Windows 2000. Let me try to test on a Linux machine.

 

[singh]

Just tested on a Linux machine with gcc. No problems. Are you sure the program doesn't work?

 

[trilobyte]

Ug?? HOW THE HELL! I get segmentation errors :/

can you paste your makefile?

 

[singh]

Originally posted by: trilobyte
Ug?? HOW THE HELL! I get segmentation errors :/

can you paste your makefile?

No makefile. Here's the run output:

student% gcc book.c bookmain.c
student% a.out*
Enter a file name: x.txt
Enter 'r' for input or 'w' for output : r
Enter a file name: y.txt
Enter 'r' for input or 'w' for output : r
TWAIN
Bayler

 

[trilobyte]

What's that a.out*?

 

[singh]

Originally posted by: trilobyte
What's that a.out*?

Executable output by gcc.

 

[trilobyte]

Hrm, my linux box doesn't seem to output any a.out from gcc, nor does the unix system at school. lemme try cygwin

 

[trilobyte]

NM the post just above, was typing it in wrong.

anyway, i'm still getting "Segmentation Fault (core dumped)" :/ that's too weird how yours works though

 

[singh]

Originally posted by: trilobyte
Hrm, my linux box doesn't seem to output any a.out from gcc, nor does the unix system at school. lemme try cygwin

Its just the default executable name; it could be anything.

 

[ynotravid]

Try using &nbsp ; to format your code.

It will allow you to use leading spaces like this:

while()
{
do this
then this
etc...
}

Or rather, it will insert spaces where you want them.

 

[ynotravid]

& n b s p ; without the spaces.

 

[m0ti]

well, here's at least one of your problems:

it's a fairly common mistake that's made by programmers in C (especially when going back from C++/Java):

typedef char* string


...

string first, last;

what this translates to is:

char* first, last;

which in C is:

char* first;
char last;

The * is ALWAYS only applicable to the first one.

And that's why you can't access the last name. You're trying to set a charcter up as a pointer, something which will give you dubious results.

Set it up as:

string first;
string last;

And this problem may well disappear.


Good luck!

 

[trilobyte]

Woohoo! It's working! No more segment errors!!

Thanks a whole bunch to everyone for trying to help. It was my malloc statement in my makeNode function. What happened was I got mixed up with my typedefs and should have done sizeof(bookType) instead of bookPtr (which was typed def'ed to * bookType). Anyway, *whew* it's working like a charm now.

Thanks again!

 

[VirtualLarry]

Originally posted by: m0ti
well, here's at least one of your problems:

it's a fairly common mistake that's made by programmers in C (especially when going back from C++/Java):

typedef char* string


...

string first, last;

what this translates to is:

char* first, last;

which in C is:

char* first;
char last;

The * is ALWAYS only applicable to the first one.

Might want to double-check your language reference manual.
What you wrote might be correct in terms of a define pre-processor macro, as those are literal replacements, but not with a typedef. Typedefs are semantic replacements.

So in fact it does translate to:

char* first, char* last;

That is not the cause of the error in the program.