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* use new a_crash() asm to optimize double-free handler.Rich Felker2011-08-231-2/+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.
* simplify and improve double-free checkRich Felker2011-08-151-2/+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).
* eliminate OOB array hacks in mallocRich Felker2011-06-261-46/+45
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* malloc: cast size down to int in bin_index functionsRich Felker2011-06-121-2/+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.
* use volatile pointers for intentional-crash code.Rich Felker2011-06-061-2/+2
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* namespace fixes for sys/mman.hRich Felker2011-04-201-0/+1
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* fix rare but nasty under-allocation bug in malloc with large requestsRich Felker2011-04-041-1/+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).
* avoid over-allocation of brk on first mallocRich Felker2011-04-011-4/+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.
* very cheap double-free checks in mallocRich Felker2011-03-231-0/+4
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* make malloc(0) return unique pointers rather than NULLRich Felker2011-02-201-5/+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.
* initial check-in, version 0.5.0 v0.5.0Rich Felker2011-02-121-0/+515