What's wrong?
Author
I have a dll creating some data using malloc(). I pass a pointer to the data to another program. Then later the other program calls free() on it.
The problem is, it crashes. Why? It''s really simple code, and I don''t know why it could be crashing.
Also, the pointer is a char*. When I tell my other program to print the data, it prints it fine, but then there''s some garbage at the end.
Any ideas?? Thoughts?
Author
The infamous "other program":
And the DLL code for GetDataFromArchive():
And in case anyone's curious, GetFilesize():
[edited by - BradDaBug on July 27, 2002 1:56:37 PM]
CFile *fp = OpenArchive("woo.txt"); char *p = GetDataFromArchive("woo.txt", fp);printf("file = %s", p);free(p);//Close archiveCloseArchive(fp); And the DLL code for GetDataFromArchive():
char *GetDataFromArchive(char *filename, CFile *file){ //Check our parameters if ((filename == NULL) || (file == NULL)) return(NULL); //Check and see if our CFile points to an open file if (file->fp == NULL) return(NULL); //Copy the file to memory char *p = NULL; p = (char*)malloc(GetFilesize(file->Filename)); rewind(file->fp); fread(p, GetFilesize(file->Filename), 1, file->fp); return(p);} And in case anyone's curious, GetFilesize():
int GetFilesize(char *filename){ int Size = 0; FILE *fp = fopen(filename, "rb"); if (fp == NULL) return(-1); fseek(fp, 0, SEEK_END); Size = ftell(fp); fclose(fp); return(Size);} [edited by - BradDaBug on July 27, 2002 1:56:37 PM]
Are you sure that the program is crashing when free() is called, because I think it could actually be the FILE* in CFile, because in my experience any attempt to use a FILE* that was not created by the file that is being executed now (example : fopen in exe, currently in dll) will cause a access violation or something similar. Just a thought.
Author
After doing away with the GetDataFromArchive() function and replacing it with a ReadFromArchive() that doesn''t allocate the memory, but instead takes a pointer to already allocated memory, it doesn''t crash anymore.
At first I figured I could easily get back a pointer to data that was created in the DLL, since DirectX does it all the time, but apparently if I try to free() it, bad things happen. I thought about putting a function in the DLL to free the created memory, but I decided I''d rather do the memory stuff myself, since I can then allocate memory once and reuse it many times.
At first I figured I could easily get back a pointer to data that was created in the DLL, since DirectX does it all the time, but apparently if I try to free() it, bad things happen. I thought about putting a function in the DLL to free the created memory, but I decided I''d rather do the memory stuff myself, since I can then allocate memory once and reuse it many times.
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