@matheusbsbs / matheus-bagliano / commits / a1293ef7c3

read-cache.c: drop PROT_WRITE from mmap of index

Once upon a time, git's in-memory representation of a cache entry actually pointed to the mmap'd on-disk data. So in 520fc24 (Allow writing to the private index file mapping., 2005-04-26), we specified PROT_WRITE so that we could tweak the entries while we run (in our own MAP_PRIVATE copy-on-write version, of course). Later, 7a51ed6 (Make on-disk index representation separate from in-core one, 2008-01-14) stopped doing this; we copy the data into our in-core representation, and then drop the mmap immediately. We can therefore drop the PROT_WRITE flag. It's probably not hurting anything as it is, but it's potentially confusing. Note that we could also mark the mapping as "const" to verify that we never write to it. However, we don't typically do that for our other maps, as it then requires casting to munmap() it. Signed-off-by: Jeff King <peff@peff.net> Signed-off-by: Junio C Hamano <gitster@pobox.com>

Jeff King committed May 28, 2015 at 03:54 UTC a1293ef7c3690829a6ac47fc45f3f26b96b5c9f5

1 file changed +1 -1

read-cache.c

+1 -1

@@ -1525,7 +1525,7 @@ int do_read_index(struct index_state *istate, const char *path, int must_exist)

1525 if (mmap_size < sizeof(struct cache_header) + 20)

1526 die("index file smaller than expected");

1527

1528 - mmap = xmmap(NULL, mmap_size, PROT_READ | PROT_WRITE, MAP_PRIVATE, fd, 0);

1528 + mmap = xmmap(NULL, mmap_size, PROT_READ, MAP_PRIVATE, fd, 0);

1529 if (mmap == MAP_FAILED)

1530 die_errno("unable to map index file");

1531 close(fd);