path: root/src/malloc/malloc.c
AgeCommit message (Collapse)AuthorLines
2011-11-16fix issue with excessive mremap syscalls on reallocRich Felker-4/+2
CHUNK_SIZE macro was defined incorrectly and shaving off at least one significant bit in the size of mmapped chunks, resulting in the test for oldlen==newlen always failing and incurring a syscall. fortunately i don't think this issue caused any other observable behavior; the definition worked correctly for all non-mmapped chunks where its correctness matters more, since their lengths are always multiples of the alignment.
2011-08-23use new a_crash() asm to optimize double-free handler.Rich Felker-2/+2
gcc generates extremely bad code (7 byte immediate mov) for the old null pointer write approach. it should be generating something like "xor %eax,%eax ; mov %al,(%eax)". in any case, using a dedicated crashing opcode accomplishes the same thing in one byte.
2011-08-15simplify and improve double-free checkRich Felker-2/+2
a valid mmapped block will have an even (actually aligned) "extra" field, whereas a freed chunk on the heap will always have an in-use neighbor. this fixes a potential bug if mmap ever allocated memory below the main program/brk (in which case it would be wrongly-detected as a double-free by the old code) and allows the double-free check to work for donated memory outside of the brk area (or, in the future, secondary heap zones if support for their creation is added).
2011-06-26eliminate OOB array hacks in mallocRich Felker-46/+45
2011-06-12malloc: cast size down to int in bin_index functionsRich Felker-2/+2
even if size_t was 32-bit already, the fact that the value was unsigned and that gcc is too stupid to figure out it would be positive as a signed quantity (due to the immediately-prior arithmetic and conditionals) results in gcc compiling the integer-to-float conversion as zero extension to 64 bits followed by an "fildll" (64 bit) instruction rather than a simple "fildl" (32 bit) instruction on x86. reportedly fildll is very slow on certain p4-class machines; even if not, the new code is slightly smaller.
2011-06-06use volatile pointers for intentional-crash code.Rich Felker-2/+2
2011-04-20namespace fixes for sys/mman.hRich Felker-0/+1
2011-04-04fix rare but nasty under-allocation bug in malloc with large requestsRich Felker-1/+1
the bug appeared only with requests roughly 2*sizeof(size_t) to 4*sizeof(size_t) bytes smaller than a multiple of the page size, and only for requests large enough to be serviced by mmap instead of the normal heap. it was only ever observed on 64-bit machines but presumably could also affect 32-bit (albeit with a smaller window of opportunity).
2011-04-01avoid over-allocation of brk on first mallocRich Felker-4/+4
if init_malloc returns positive (successful first init), malloc will retry getting a chunk from the free bins rather than expanding the heap again. also pass init_malloc a hint for the size of the initial allocation.
2011-03-23very cheap double-free checks in mallocRich Felker-0/+4
2011-02-20make malloc(0) return unique pointers rather than NULLRich Felker-5/+9
this change is made with some reluctance, but i think it's for the best. correct programs must handle either behavior, so there is little advantage to having malloc(0) return NULL. and i managed to actually make the malloc code slightly smaller with this change.
2011-02-12initial check-in, version 0.5.0v0.5.0Rich Felker-0/+515