about summary refs log tree commit diff
path: root/src/malloc/calloc.c
Commit message (Collapse)AuthorAgeFilesLines
* reintroduce calloc elison of memset for direct-mmapped allocationsRich Felker2020-06-101-1/+9
| | | | | | | | | | | | | | a new weak predicate function replacable by the malloc implementation, __malloc_allzerop, is introduced. by default it's always false; the default version will be used when static linking if the bump allocator was used (in which case performance doesn't matter) or if malloc was replaced by the application. only if the real internal malloc is linked (always the case with dynamic linking) does the real version get used. if malloc was replaced dynamically, as indicated by __malloc_replaced, the predicate function is ignored and conditional-memset is always performed.
* switch to a common calloc implementationRich Felker2020-06-101-0/+37
| | | | | | | | | | | | | | | | | | | | | | | | | | abstractly, calloc is completely malloc-implementation-independent; it's malloc followed by memset, or as we do it, a "conditional memset" that avoids touching fresh zero pages. previously, calloc was kept separate for the bump allocator, which can always skip memset, and the version of calloc provided with the full malloc conditionally skipped the clearing for large direct-mmapped allocations. the latter is a moderately attractive optimization, and can be added back if needed. however, further consideration to make it correct under malloc replacement would be needed. commit b4b1e10364c8737a632be61582e05a8d3acf5690 documented the contract for malloc replacement as allowing omission of calloc, and indeed that worked for dynamic linking, but for static linking it was possible to get the non-clearing definition from the bump allocator; if not for that, it would have been a link error trying to pull in malloc.o. the conditional-clearing code for the new common calloc is taken from mal0_clear in oldmalloc, but drops the need to access actual page size and just uses a fixed value of 4096. this avoids potentially needing access to global data for the sake of an optimization that at best marginally helps archs with offensively-large page sizes.
* allow interposition/replacement of allocator (malloc)Rich Felker2018-04-181-13/+0
| | | | | | | | | | | | | | | | | | | | | | | replacement is subject to conditions on the replacement functions. they may only call functions which are async-signal-safe, as specified either by POSIX or as an implementation-defined extension. if any allocator functions are replaced, at least malloc, realloc, and free must be provided. if calloc is not provided, it will behave as malloc+memset. any of the memalign-family functions not provided will fail with ENOMEM. in order to implement the above properties, calloc and __memalign check that they are using their own malloc or free, respectively. choice to check malloc or free is based on considerations of supporting __simple_malloc. in order to make this work, calloc is split into separate versions for __simple_malloc and full malloc; commit ba819787ee93ceae94efd274f7849e317c1bff58 already did most of the split anyway, and completing it saves an extra call frame. previously, use of -Bsymbolic-functions made dynamic interposition impossible. now, we are using an explicit dynamic-list, so add allocator functions to the list. most are not referenced anyway, but all are added for completeness.
* fix calloc when __simple_malloc implementation is usedRich Felker2015-06-221-12/+3
| | | | | | | | | | | | | | | | | previously, calloc's implementation encoded assumptions about the implementation of malloc, accessing a size_t word just prior to the allocated memory to determine if it was obtained by mmap to optimize out the zero-filling. when __simple_malloc is used (static linking a program with no realloc/free), it doesn't matter if the result of this check is wrong, since all allocations are zero-initialized anyway. but the access could be invalid if it crosses a page boundary or if the pointer is not sufficiently aligned, which can happen for very small allocations. this patch fixes the issue by moving the zero-fill logic into malloc.c with the full malloc, as a new function named __malloc0, which is provided by a weak alias to __simple_malloc (which always gives zero-filled memory) when the full malloc is not in use.
* include cleanups: remove unused headers and add feature test macrosSzabolcs Nagy2013-12-121-1/+0
|
* initial check-in, version 0.5.0 v0.5.0Rich Felker2011-02-121-0/+23