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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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bsdmalloc(3MALLOC)														bsdmalloc(3MALLOC)

NAME
bsdmalloc - memory allocator SYNOPSIS
cc [ flag ... ] file ... -lbsdmalloc [ library ... ] char *malloc(size); unsigned size; int free( ptr); char *ptr; char *realloc( ptr, size); char *ptr; unsigned size; These routines provide a general-purpose memory allocation package. They maintain a table of free blocks for efficient allocation and coa- lescing of free storage. When there is no suitable space already free, the allocation routines call sbrk(2) to get more memory from the system. Each of the allocation routines returns a pointer to space suitably aligned for storage of any type of object. Each returns a null pointer if the request cannot be completed. The malloc() function returns a pointer to a block of at least size bytes, which is appropriately aligned. The free() function releases a previously allocated block. Its argument is a pointer to a block previously allocated by malloc() or real- loc(). The free() function does not set errno. The realloc() function changes the size of the block pointed to by ptr to size bytes and returns a pointer to the (possibly moved) block. The contents will be unchanged up to the lesser of the new and old sizes. If the new size of the block requires movement of the block, the space for the previous instantiation of the block is freed. If the new size is larger, the contents of the newly allocated portion of the block are unspecified. If ptr is NULL, realloc() behaves like malloc() for the specified size. If size is 0 and ptr is not a null pointer, the space pointed to is freed. The malloc() and realloc() functions return a null pointer if there is not enough available memory. They return a non-null pointer if size is 0. These pointers should not be dereferenced. When realloc() returns NULL, the block pointed to by ptr is left intact. Always cast the value returned by malloc() and realloc(). If malloc() or realloc() returns unsuccessfully, errno will be set to indicate the following: ENOMEM size bytes of memory cannot be allocated because it exceeds the physical limits of the system. EAGAIN There is not enough memory available at this point in time to allocate size bytes of memory; but the application could try again later. Using realloc() with a block freed before the most recent call to malloc() or realloc() results in an error. Comparative features of the various allocation libraries can be found in the umem_alloc(3MALLOC) manual page. brk(2), malloc(3C), malloc(3MALLOC), mapmalloc(3MALLOC), umem_alloc(3MALLOC) WARNINGS
Use of libbsdmalloc renders an application non-SCD compliant. The libbsdmalloc routines are incompatible with the memory allocation routines in the standard C-library (libc): malloc(3C), alloca(3C), calloc(3C), free(3C), memalign(3C), realloc(3C), and valloc(3C). 21 Mar 2005 bsdmalloc(3MALLOC)
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