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Rewrite Cosmopolitan Ar

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The build/bootstrap/ar.com program is now tinier. This change reduces
its size from 140kb to 53kb. Nothing was traded away. Cosmopolitan Ar
performance is now 2x better than llvm-ar largely thanks to using the
copy_file_range() system call. This change homebrews a new allocation
API that addresses the shortcomings of the C standard library design.
Using these new balloc() and reballoc() functions I managed to reduce
memory consumption so much that Cosmpolitan Ar should now use roughly
100x fewer bytes of peak resident memory compared to llvm-ar. Correct
behavior with better compatibility has been assured. Binary output is
now pretty much bit-identical to llvm-ar, as of this change. This can
and should be the living proof we need to show that a better world is
possible for software.
This commit is contained in:
Justine Tunney 2023-07-02 10:19:16 -07:00
parent 197aa0d465
commit 0c630d95b5
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27 changed files with 916 additions and 341 deletions
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16
libc/elf/getelfsectionheaderaddress.c
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@ -16,21 +16,29 @@
│ TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR │
│ PERFORMANCE OF THIS SOFTWARE. │
╚─────────────────────────────────────────────────────────────────────────────*/
#include "libc/elf/def.h"
#include "libc/elf/elf.h"
#include "libc/elf/scalar.h"
#include "libc/elf/struct/shdr.h"
/**
* Returns section header object at `elf.section[i]`.
*
* @param elf points to the start of the executable image
* @param elf points to the start of the executable image data
* @param mapsize is the number of bytes past `elf` we can access
* @param i is the section header index, starting at zero
* @return section header pointer, or null on error
* @param i is the index of the section header
* @return pointer to section header within image, or null if
* 1. `i` was a magic number, i.e. `i >= SHN_LORESERVE`, or
* 2. `e_shoff` was zero (image has no section headers), or
* 3. `e_shentsize` had fewer than the mandatory 60 bytes, or
* 4. section header wasn't contained by `[elf,elf+mapsize)`, or
* 5. an arithmetic overflow occurred
*/
Elf64_Shdr *GetElfSectionHeaderAddress(const Elf64_Ehdr *elf, //
size_t mapsize, //
Elf64_Half i) { //
uint64_t off;
Elf64_Off off;
if (i >= SHN_LORESERVE) return 0;
if (i >= elf->e_shnum) return 0;
if (elf->e_shoff <= 0) return 0;
if (elf->e_shoff >= mapsize) return 0;