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Aug 21st, 2009

malloc does not allocate beyond 65872

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Hi,
I need an array of approx. 2,00,000 elements.But malloc fails to allocate beyond 65872.
When I give
(short int*)malloc(sizeof(short int)*65000);
It works but seg faults when I give
(short int*)malloc(sizeof(short int)*66000);

whatsup with that?

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AutoC

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Aug 21st, 2009

Re: malloc does not allocate beyond 65872

What compiler do you use?

Tom Gunn

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Aug 21st, 2009

Re: malloc does not allocate beyond 65872

gcc

AutoC

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Aug 21st, 2009

Re: malloc does not allocate beyond 65872

Now why are you casting the result of malloc?

Could it be that you didn't include stdlib.h and thus the compiler considers malloc as returning an int rather than a pointer?
This can be a well hidden and very obscure bug.

> I need an array of approx. 2,00,000 elements.But malloc fails to allocate beyond 65872.
Is this the only malloc call in your program?
Is it really an array of short int's, as the casting suggests?

If any previously allocated memory was screwed up (say by a buffer overrun), then anything could be happening. Staring at one line of code which is perfect if run in isolation won't solve it.

Salem

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Aug 25th, 2009

Re: malloc does not allocate beyond 65872

Click to Expand / Collapse Quote originally posted by Salem ...

Now why are you casting the result of malloc?

Could it be that you didn't include stdlib.h and thus the compiler considers malloc as returning an int rather than a pointer?
This can be a well hidden and very obscure bug.

> I need an array of approx. 2,00,000 elements.But malloc fails to allocate beyond 65872.
Is this the only malloc call in your program?
Is it really an array of short int's, as the casting suggests?

If any previously allocated memory was screwed up (say by a buffer overrun), then anything could be happening. Staring at one line of code which is perfect if run in isolation won't solve it.

I've included stdlib,no problem there.
Yes.It is an array of short ints
Here is the entire function

Quote ...

int WriteRIFF( char *waveFileName, short *waveform, long numsamples, long samplingRate, int bytesPerSample)
{
FILE *file;
RIFFWaveFile *myRIFF = NULL;
long i = 0;
long size = 0;
int result = SUCCESS;
file = fopen(waveFileName, "w");
myRIFF = (RIFFWaveFile *)malloc(sizeof(RIFFWaveFile));
myRIFF->header = (RIFFHeader *)malloc(sizeof(RIFFHeader));

strcpy(myRIFF->header->riffChunkID, "RIFF");
myRIFF->header->riffChunkDataSize = numsamples*2 + 36;
strcpy(myRIFF->header->riffType, "WAVE");

strcpy(myRIFF->header->fmtChunkID,"fmt ");
myRIFF->header->fmtChunkDataSize = 16;
myRIFF->header->compressionCode = 1;
myRIFF->header->numberOfChannel = 1;
myRIFF->header->sampleRate = samplingRate;
myRIFF->header->averageBytesPerSecond = bytesPerSample*samplingRate;
myRIFF->header->blockAlign = 2;
myRIFF->header->sigBitsPerSample = bytesPerSample*8;

strcpy(myRIFF->header->dataChunkID,"data");
myRIFF->header->dataChunkDataSize = numsamples*2;
size = myRIFF->header->dataChunkDataSize/2;

/* This is where the problem is */

myRIFF->data = (short int*)malloc(sizeof(short int)*size);
for(i=0; i <size; i++)
{
myRIFF->data[i] = waveform[i];
}

RiffWaveFile and RiffHeader are structures as follows.

Quote ...

typedef unsigned char UCHAR;
typedef short int INT;
typedef long DWORD;

typedef struct RIFFHeader
{
UCHAR riffChunkID[4]; //0x00
DWORD riffChunkDataSize; //0x04
UCHAR riffType[4]; //0x08

UCHAR fmtChunkID[4]; //0x0C
DWORD fmtChunkDataSize; //0x10
INT compressionCode; //0x14
INT numberOfChannel; //0x16
DWORD sampleRate; //0x18
DWORD averageBytesPerSecond; //0x1C
INT blockAlign; //0x20
INT sigBitsPerSample; //0x22

//@ This Element is not present for Uncompressed/PCM format
//INT numberOfExtraBytes __attribute__ ((packed)); //0x24

UCHAR dataChunkID[4]; //0x24
DWORD dataChunkDataSize; //0x28

}RIFFHeader __attribute__ ((packed));

typedef struct RIFFWaveFile
{
RIFFHeader *header; //0x00 to 0x2B
short int *data __attribute__ ((packed)); //0x2C to dataSize

}RIFFWaveFile;

Last edited by AutoC; Aug 25th, 2009 at 8:10 am.

AutoC

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Aug 25th, 2009

Re: malloc does not allocate beyond 65872

well malloc is defined as

C Syntax (Toggle Plain Text)
 void *malloc(size_t size);
 void *malloc(size_t size);

and size_t is probably 64kb is your computer.
use farmalloc.

http://vitaly_filatov.tripod.com/ng/tc/tc_000.78.html

this is a function that allows you to allocate more than 64kb
hope it helps

Last edited by aflneto; Aug 25th, 2009 at 8:18 am.

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Aug 25th, 2009

Re: malloc does not allocate beyond 65872

that doesnt seem to be the problem. The input to the function short int *waveform was initialized in a similar manner.It didnt cause a problem.

AutoC

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Aug 25th, 2009

Re: malloc does not allocate beyond 65872

What I was trying to say malloc cant allocate that much memory. It can allocate a maximum of 64kb of memory in one go.
Hence why

C Syntax (Toggle Plain Text)
 (short int*)malloc(sizeof(short int)*65000);
 (short int*)malloc(sizeof(short int)*65000);

works, but

C Syntax (Toggle Plain Text)
(short int*)malloc(sizeof(short int)*66000);
(short int*)malloc(sizeof(short int)*66000);

fails
answering your original question.
farmalloc() function on the other hand allows you to allocate blocks larger than 64kb.

Last edited by aflneto; Aug 25th, 2009 at 9:26 am.

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Aug 25th, 2009

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Re: malloc does not allocate beyond 65872

As far as I can tell farmalloc() is only implemented on 16-bit compilers. There is no such thing as a "far heap" in 32 (or more)-bit programs because they use the flat memory model where all memory is considered near.

Last edited by Ancient Dragon; Aug 25th, 2009 at 10:09 am.

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Aug 25th, 2009

Re: malloc does not allocate beyond 65872

I just realized how stupid I was being! also,farmalloc is a function implemented for windows as well. Sorry for not being helpful!

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