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fread: segementation fault(coredump) w/o stdlib.h
Post 302286608 by Corona688 on Wednesday 11th of February 2009 02:23:54 PM
02-11-2009
As the doctor would say, "don't do that". 
Either AIX has odd integer sizes, or you're on a 64-bit system. Or perhaps both.
When you use functions that you haven't included headers for, the compiler's forced to guess what parameters the function takes and returns, and will guess they are all integers. This is often a good guess on most 32-bit systems, where int, long, and all pointers are the same size -- 32 bits. But 64-bit systems will have 64-bit pointers while still perhaps having 32-bit integers, causing pointers to get balled up and crammed through the mail slot, so to speak.
Without stdlib.h, the value malloc() gives you is corrupted, causing fread to crash when it uses it.
So, always include the headers! Just because it works 'this time' when you don't doesn't mean it will in all situations.
Either AIX has odd integer sizes, or you're on a 64-bit system. Or perhaps both.When you use functions that you haven't included headers for, the compiler's forced to guess what parameters the function takes and returns, and will guess they are all integers. This is often a good guess on most 32-bit systems, where int, long, and all pointers are the same size -- 32 bits. But 64-bit systems will have 64-bit pointers while still perhaps having 32-bit integers, causing pointers to get balled up and crammed through the mail slot, so to speak.
Without stdlib.h, the value malloc() gives you is corrupted, causing fread to crash when it uses it.
So, always include the headers! Just because it works 'this time' when you don't doesn't mean it will in all situations.
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ftello
FTELL(P) POSIX Programmer's Manual FTELL(P) NAME
ftell, ftello - return a file offset in a stream SYNOPSIS
#include <stdio.h> long ftell(FILE *stream); off_t ftello(FILE *stream); DESCRIPTION
The ftell() function shall obtain the current value of the file-position indicator for the stream pointed to by stream. The ftello() function shall be equivalent to ftell(), except that the return value is of type off_t. RETURN VALUE
Upon successful completion, ftell() and ftello() shall return the current value of the file-position indicator for the stream measured in bytes from the beginning of the file. Otherwise, ftell() and ftello() shall return -1, cast to long and off_t respectively, and set errno to indicate the error. ERRORS
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None. APPLICATION USAGE
None. RATIONALE
None. FUTURE DIRECTIONS
None. SEE ALSO
fgetpos() , fopen() , fseek() , lseek() , the Base Definitions volume of IEEE Std 1003.1-2001, <stdio.h> COPYRIGHT
Portions of this text are reprinted and reproduced in electronic form from IEEE Std 1003.1, 2003 Edition, Standard for Information Technol- ogy -- Portable Operating System Interface (POSIX), The Open Group Base Specifications Issue 6, Copyright (C) 2001-2003 by the Institute of Electrical and Electronics Engineers, Inc and The Open Group. In the event of any discrepancy between this version and the original IEEE and The Open Group Standard, the original IEEE and The Open Group Standard is the referee document. The original Standard can be obtained online at http://www.opengroup.org/unix/online.html . IEEE
/The Open Group 2003 FTELL(P)