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MALLOC(3) BSD Library Functions Manual MALLOC(3) NAME calloc, free, malloc, realloc, reallocf, valloc -- memory allocation SYNOPSIS #include <stdlib.h> void * calloc(size_t count, size_t size); void free(void *ptr); void * malloc(size_t size); void * realloc(void *ptr, size_t size); void * reallocf(void *ptr, size_t size); void * valloc(size_t size); DESCRIPTION The malloc(), calloc(), valloc(), realloc(), and reallocf() functions allocate memory. The allocated memory is aligned such that it can be used for any data type, including AltiVec- and SSE-related types. The free() function frees allocations that were created via the preceding allocation functions. The malloc() function allocates size bytes of memory and returns a pointer to the allocated memory. The calloc() function contiguously allocates enough space for count objects that are size bytes of memory each and returns a pointer to the allocated memory. The allocated memory is filled with bytes of value zero. The valloc() function allocates size bytes of memory and returns a pointer to the allocated memory. The allocated memory is aligned on a page boundary. The realloc() function tries to change the size of the allocation pointed to by ptr to size, and returns ptr. If there is not enough room to enlarge the memory allocation pointed to by ptr, realloc() creates a new allocation, copies as much of the old data pointed to by ptr as will fit to the new allocation, frees the old allocation, and returns a pointer to the allocated memory. If ptr is NULL, realloc() is identical to a call to malloc() for size bytes. If size is zero and ptr is not NULL, a new, minimum sized object is allocated and the original object is freed. The reallocf() function is identical to the realloc() function, except that it will free the passed pointer when the requested memory cannot be allocated. This is a FreeBSD specific API designed to ease the problems with traditional coding styles for realloc causing memory leaks in libraries. The free() function deallocates the memory allocation pointed to by ptr. RETURN VALUES If successful, calloc(), malloc(), realloc(), reallocf(), and valloc() functions return a pointer to allocated memory. If there is an error, they return a NULL pointer and set errno to ENOMEM. For realloc(), the input pointer is still valid if reallocation failed. For reallocf(), the input pointer will have been freed if reallocation failed. The free() function does not return a value. DEBUGGING ALLOCATION ERRORS A number of facilities are provided to aid in debugging allocation errors in applications. These facilities are primarily controlled via environ-ment environment ment variables. The recognized environment variables and their meanings are documented below. ENVIRONMENT The following environment variables change the behavior of the alloca-tion-related allocation-related tion-related functions. MallocLogFile <f> Create/append messages to the given file path <f> instead of writing to the standard error. MallocGuardEdges If set, add a guard page before and after each large block. MallocDoNotProtectPrelude If set, do not add a guard page before large blocks, even if the MallocGuardEdges envi-ronment environment ronment variable is set. MallocDoNotProtectPostlude If set, do not add a guard page after large blocks, even if the MallocGuardEdges envi-ronment environment ronment variable is set. MallocStackLogging If set, record all stacks, so that tools like leaks can be used. MallocStackLoggingNoCompact If set, record all stacks in a manner that is compatible with the malloc_history pro-gram. program. gram. MallocPreScribble If set, fill memory that has been allocated with 0xaa bytes. This increases the likeli-hood likelihood hood that a program making assumptions about the contents of freshly allocated memory will fail. MallocScribble If set, fill memory that has been deallo-cated deallocated cated with 0x55 bytes. This increases the likelihood that a program will fail due to accessing memory that is no longer allo-cated. allocated. cated. MallocCheckHeapStart <s> If set, specifies the number of allocations <s> to wait before begining periodic heap checks every <n> as specified by MallocCheckHeapEach. If MallocCheckHeapStart is set but MallocCheckHeapEach is not specified, the default check repetition is 1000. MallocCheckHeapEach <n> If set, run a consistency check on the heap every <n> operations. MallocCheckHeapEach is only meaningful if MallocCheckHeapStart is also set. MallocCheckHeapSleep <t> Sets the number of seconds to sleep (waiting for a debugger to attach) when MallocCheckHeapStart is set and a heap cor-ruption corruption ruption is detected. The default is 100 seconds. Setting this to zero means not to sleep at all. Setting this to a negative number means to sleep (for the positive num-ber number ber of seconds) only the very first time a heap corruption is detected. MallocCheckHeapAbort <b> When MallocCheckHeapStart is set and this is set to a non-zero value, causes abort(3) to be called if a heap corruption is detected, instead of any sleeping. MallocErrorAbort If set, causes abort(3) to be called if an error was encountered in malloc(3) or free(3) , such as a calling free(3) on a pointer previously freed. MallocHelp If set, print a list of environment vari-ables variables ables that are paid heed to by the alloca-tion-related allocation-related tion-related functions, along with short descriptions. The list should correspond to this documentation. DIAGNOSTIC MESSAGES SEE ALSO leaks(1), malloc_history(1), abort(3), malloc_size(3) /Developer/ADC Reference Library/releasenotes/DeveloperTools/MallocOptions.html BSD May 23, 2006 BSD |