Re: Malloc code

Hello David Wilk.

I am glad that you have resolved your issue, if indeed you have. If your
problem was that you were assigning too much memory, why did did
malloc() not return NULL?

I haven't got the slightest clue! I will re-test it and see.

David, excuse my ignorance, but what do you mean by top-post? :-(


2. I did notice that there were several hard coded constants in your
code (11, 12, 15, 16, 176) and wondered what their purpose was.

David: can you let me know where you see this? And its in the clearer code
sample that you see this, right? I know that I assign bogus numbers in the
TCP_LOAD_MCB_X() function. Is this what you mean?


You could have gotten rid of the particular problem you had by doing
#define NMAX 11 /* or 12 ? */
pMCB1 = malloc(NMAX*(sizeof(struct MCB)));
for (i=0; i<NMAX; i++)

Yes indeed I could of done this, but actually do it in the full blown
project code!

Although I did guess that xxx was being used only for debugging
purposes, it would have been nice if this had been indicated in the code:
int xxx[12]; /* for debugging only */

You bet I will indicate this next time! I think I confused alot of people
with that !

I didin't know that we can insert a file in our posts! I will need to figure
out how to do this.

6. I understand that you are using some embedded compiler, but this is a
vc group. It would be god if you were to try your code in vc, and see if
the problem is still there. If not, it is unlikely that anybody here can
help you with it; but if so, this may be a big clue.

I thought of doing that, but you see, its 2 years I have not done any vc++
because, I really had to get the embeded stuff of my project done first (man,
I didn't think it would take me so long). So, when I posted this post a
couple of days ago, I did try it in vc++ by reproducing the three files and
copying the code, but it gave me over 150 errors. And then with all of the
discouragment I was going through with this post, I just gave up and closed
vc++. But, I really can't wait to pick it up again in the near future...
theres so much I want to learn.

Thanks for the clue... But this site is very good and there is alot of
resourcefull help.
You guys also helped me alot with vc++. I apologize if this post was so
unclear but this was a nasty one.

Also, since David Web. has reccomended to not declare pointers in my header,
this sort of complicated things where I must now assign all the pointers
returned from malloc to an array of pointers, and then return this array of
pointers back to main, which I have never done before. I did start coding it.
I know how to pass in an array of pointers. But don't know how to return an
array of pointers. So I just returned a void pointer and assign the value to
another pointer declared in main. I read up on some samples which showed some
examples but didn't show how to do this exactly the way I needed it. This is
what I came up with and it compiles but I did not test it yet. This will be
done tomorrow. I was also curious, is there another way where I can pass back
the actual array of pointers from the function instead of a void pointer?
Anyways here is what I have done.

void *FX()
{
struct MCB *MCBptrs[3]; //Array of pointers
MCBptrs[0] = malloc(10*(sizeof(struct MCB)));
MCBptrs[1] = malloc(20*(sizeof(struct MCB)));
MCBptrs[2] = malloc(30*(sizeof(struct MCB)));
return MCBptrs;
}


void main()
{
int *gptr;
struct MCB *r1;
struct MCB *r2;
struct MCB *r3;

gptr = (int *) FX();

r1 = *gptr[0];
r2 = *gptr[1];
r3 = *gptr[2];

r1[0].LEADING_PIX;
r2[2].LEADING_PIX;
r3[7].LEADING_PIX;

free(*gptr[0]);
free(*gptr[1]);
free(*gptr[2]);
}


Thankyou for your post, hope you had a nice new year's eve!

--
Best regards
Robert


"David Wilkinson" wrote:

Robby wrote:
Hello to both Davids! Thankyou for replying!

David Wil. , your right I can just free it in main since the pointer to that
allocation is passed back to main. Sorry!

2. This code may be clearer than before, but it is full of functions
that do nothing but call other functions, functions that have no
external effect, and local variables that are assigned but not used.

Since I wanted to be represent as precice as possible the code in my actual
project, I included all the functions involved, but they do include other
code which is not pertinant to my problem... I just included them in case
they would some how be the source of the problem which I now doubt it very
much!.... so thats why they are there. I mean you can just ignore them. If
you wish I can start a new post called "Malloc code 2" and exclude these
functions and some other non relevent stuff.

David Web. BAD_POINTER should of been atleast set to 0 in its
innitialization, but the only reason I included :

if(pCL_B==NULL)
{BAD_POINTER=1;}

in my code is to show that I am aware that I should check if the pointer is
valid. But for testing purposes with the debuger, I can see if the bointer is
null by simply hovering my cursor over pCL_B as it displays its value! So for
now its not of a great concern. The urgent concern is to understand why I
read junk in the for loop of the TCP_LOAD_MCB_X function. The code sample
that was posted is far from what will actually be done as a final product. I
understand your concern and I appreciate you pointing it out and its also
good constructive critisism for me or anyone else that reads this post. (for
beginers like me that is!).

You have most probably noticed that I was using an array called "xxx[12]" in
TCP_LOAD_MCB_X and I am assigning the values to the items of the strucutre
like this:

pMCB1[i].ENDOFCHAR = 2;

and then re-assigning the value of ENDOFCHAR to an item in the xxx array
like so:

xxx[k]= pMCB1[i].ENDOFCHAR; k++;

This is because the watch window in my compiler is not able to read the
contents of "pMCB1[i].ENDOFCHAR". This is a known issue to them and are
currently working on it. Therefore in my code (as you have probably noticed)
I assign the value to the structure's item and then to assure that it really
was assigned I check it via the xxx[] array. As soon as the compiler's
company come up with a fix, I will remove the xxx array in its entirety. I
know its sad, but I have no choice! So this is why I do this in my code.

k=0;
pMCB1[i].ENDOFCHAR = 2;
xxx[k]= pMCB1[i].ENDOFCHAR; k++;
//etc

So when the TCP_LOAD_MCB_X function is finished assigning all the items in
every structure, I return the malloc pointer, since it was reccomended to me
that we must not loose the pointer.

Then I pass it back into the FETCH() function. In this function I declare
another array called xxx[] for the same reason I did in the TCP_LOAD_MCB_X
function.

I also do another malloc which assigns its pointer to pCL_B. Then I try to
read every item of the structures that were previously assigned in the
TCP_LOAD_MCB_X function.

So if I put:

pt[i].ENDOFCHAR;

in the watch window, my compiler cannot directly display its contents.
Therefore I assign every item of the structure to an item of the array called
xxx[]. And this is why I have this in the fetch() function:

for(i=0;i<11;i++)
{
xxx[0]= pt[i].ENDOFCHAR;
xxx[1]= pt[i].A2;
xxx[2]= pt[i].A1;
xxx[3]= pt[i].A0;
xxx[4]= pt[i].LEADING_PIX;
xxx[5]= pt[i].TRAILING_PIX;
xxx[6]= pt[i].CHARSPACING;
xxx[7]= pt[i].CHAR_TRSP;
xxx[8]= pt[i].mCHAR_BCOLOR;
xxx[9]= pt[i].lCHAR_BCOLOR;
xxx[10]= pt[i].mTEXT_COLOR;
xxx[11]= pt[i].mTEXT_COLOR;
} //<<< Break point here!

Putting a break point in the for loop shown above permits me to see a series
of 12 values contained in every structure. But some of the series are good
and some are not (Junk!)

When i = 0, I read: (error,4,6,8,10,12,14,16,18,20,22,24)
When i = 1, I read: (2,4,6,8,10,12,14,16,18,20,22,24)
When i = 2, I read: (2,4,6,8,10,12,14,16,18,20,22,24)
When i = 3, I read: (2,4,6,8,10,12,14,16,18,20,22,24)
When i = 4, I read: (2,4,6,8,10,12,14,16,18,20,22,24)
When i = 5, I read: (2,,4,6,8,30,128, 164,0,18,20,22,24) <<< wrong data!
When i = 6, I read: (2,4,6,8,10,12,14,16,18,20,22,24)
When i = 7, I read: (2,4,6,8,10,12,14,16,18,20,22,24)
When i = 8, I read: (2,11,232,8,14,16,14,16,18,20,22,24) << wrong data!
When i = 9, I read: (2,4,6,8,10,12,14,16,18,20,22,24)
When i = 10, I read: (2,4,6,8,10,12,14,16,18,20,22,24)

When I should read:

When i = 0, I read: (2,4,6,8,10,12,14,16,18,20,22,24)
When i = 1, I read: (2,4,6,8,10,12,14,16,18,20,22,24)
When i = 2, I read: (2,4,6,8,10,12,14,16,18,20,22,24)
When i = 3, I read: (2,4,6,8,10,12,14,16,18,20,22,24)
When i = 4, I read: (2,4,6,8,10,12,14,16,18,20,22,24)
When i = 5, I read: (2,4,6,8,10,12,14,16,18,20,22,24)
When i = 6, I read: (2,4,6,8,10,12,14,16,18,20,22,24)
When i = 7, I read: (2,4,6,8,10,12,14,16,18,20,22,24)
When i = 8, I read: (2,4,6,8,10,12,14,16,18,20,22,24)
When i = 9, I read: (2,4,6,8,10,12,14,16,18,20,22,24)
When i = 10, I read: (2,4,6,8,10,12,14,16,18,20,22,24)

and oops! I just tried something!

for(i=0;i<12;i++) instead of: for(i=0;i<11;i++)

and what the hell is the 176 doing there!

pMCB1 = malloc(176*(sizeof(struct MCB)));

//This allocates 2.112 KBytes, I only have 1.5Kbytes!

it should be:

pMCB1 = malloc(11*(sizeof(struct MCB)));


!!!!!!!!!!and it works!

That's it folks, I need a vacation!

C requires a vigilant mind and I am too tired! An infinate thankyou for your
support, I must admit, what gave it away was:


Robby:

I am glad that you have resolved your issue, if indeed you have. If your
problem was that you were assigning too much memory, why did did
malloc() not return NULL?

Some general comments:

1. Once again, if you must top-post, please trim previous replies. One
advantage of bottom-posting is that it virtually forces you to do some
trimming.

2. I did notice that there were several hard coded constants in your
code (11, 12, 15, 16, 176) and wondered what their purpose was. You
could have gotten rid of the particular problem you had by doing

#define NMAX 11 /* or 12 ? */

pMCB1 = malloc(NMAX*(sizeof(struct MCB)));
for (i=0; i<NMAX; i++)

3. Although I did guess that xxx was being used only for debugging
purposes, it would have been nice if this had been indicated in the code:

int xxx[12]; /* for debugging only */

By the way, you should be able to get the same diagnostic effect by doing

int* xxx;
for (i=0; i<NMAX; i++)
{
xxx = (int*)(pMCB1 + i);
// ...
}

4. You say you left the redundant functions in the code because you
thought they might be the cause of the problem. Why not take them out
yourself and find out? It is *your* job to simplify the code as much as
possible before you dump it on the newsgroup. It is also much more
convenient if you can combine the code into a single file, so that
responders can easily insert it into a vc project.

5. There are other redundant features/variables in your code that serve
no purpose at all, in particular BAD_POINTER and pCL_B. It is possible
that the latter actually causes the problem by contributing to the
memory exhaustion; if so, taking it out will tell you something.

6. I understand that you are using some embedded compiler, but this is a
vc group. It would be god if you were to try your code in vc, and see if
the problem is still there. If not, it is unlikely that anybody here can
help you with it; but if so, this may be a big clue.

Good luck!

--
David Wilkinson
Visual C++ MVP

.

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