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Full Discussion: fgets problems
Top Forums Programming fgets problems Post 302396959 by CRGreathouse on Saturday 20th of February 2010 01:24:28 AM
Old 02-20-2010
Quote:
Originally Posted by jim mcnamara
You have a lot of heap memory involvement. ie., hidden library calls to malloc - you need a malloc debugger.
Huge amounts of memory management -- much more in the calculation parts of my program. Pari essentially forces you to manage all your own memory.

But malloc itself isn't really ever called, not even in the library calls (except initialization). All the memory is allocated initially, and the program tracks usage itself. So when I write

Code:
GEN x = stoi(3); // x = 3
GEN y = stoi(4); // y = 4
GEN z = addii(x, y); // z = x + y
z = mulii(z, x); // z *= x

malloc is called zero times in that sequence, but four objects are created in a large block of memory. The block of memory (called the Pari stack -- but it's just a large malloc'd variable, really) functions as a stack, insofar as it's my responsibility to leave return values at the top and move the pointers as needed to let garbage drop off.


Do you think these programs would be able to handle such a low-level system?
 

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FGETS(3)						   BSD Library Functions Manual 						  FGETS(3)

NAME
fgets, gets -- get a line from a stream LIBRARY
Standard C Library (libc, -lc) SYNOPSIS
#include <stdio.h> char * fgets(char * restrict str, int size, FILE * restrict stream); char * gets(char *str); DESCRIPTION
The fgets() function reads at most one less than the number of characters specified by size from the given stream and stores them in the string str. Reading stops when a newline character is found, at end-of-file or error. The newline, if any, is retained. If any characters are read and there is no error, a '' character is appended to end the string. The gets() function is equivalent to fgets() with an infinite size and a stream of stdin, except that the newline character (if any) is not stored in the string. It is the caller's responsibility to ensure that the input line, if any, is sufficiently short to fit in the string. RETURN VALUES
Upon successful completion, fgets() and gets() return a pointer to the string. If end-of-file occurs before any characters are read, they return NULL and the buffer contents remain unchanged. If an error occurs, they return NULL and the buffer contents are indeterminate. The fgets() and gets() functions do not distinguish between end-of-file and error, and callers must use feof(3) and ferror(3) to determine which occurred. ERRORS
[EBADF] The given stream is not a readable stream. The function fgets() may also fail and set errno for any of the errors specified for the routines fflush(3), fstat(2), read(2), or malloc(3). The function gets() may also fail and set errno for any of the errors specified for the routine getchar(3). SEE ALSO
feof(3), ferror(3), fgetln(3), fgetws(3), getline(3) STANDARDS
The functions fgets() and gets() conform to ISO/IEC 9899:1999 (``ISO C99''). SECURITY CONSIDERATIONS
The gets() function cannot be used securely. Because of its lack of bounds checking, and the inability for the calling program to reliably determine the length of the next incoming line, the use of this function enables malicious users to arbitrarily change a running program's functionality through a buffer overflow attack. It is strongly suggested that the fgets() function be used in all cases. BSD
May 5, 2012 BSD
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