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Cast 64 bit off_t to 32 bit size_t

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Some systems have sizeof(off_t) == 8 while sizeof(size_t) == 4.
This implies that we are able to access and work on files whose
maximum length is around 2^63-1 bytes, but we can only malloc or
mmap somewhat less than 2^32-1 bytes of memory.

On such a system an implicit conversion of off_t to size_t can cause
the size_t to wrap, resulting in unexpected and exciting behavior.
Right now we are working around all gcc warnings generated by the
-Wshorten-64-to-32 option by passing the off_t through xsize_t().

In the future we should make xsize_t on such problematic platforms
detect the wrapping and die if such a file is accessed.

Signed-off-by: Shawn O. Pearce <spearce@spearce.org>
Signed-off-by: Junio C Hamano <junkio@cox.net>
This commit is contained in:
Shawn O. Pearce
2007-03-06 20:44:37 -05:00
committed by Junio C Hamano
parent 6777a59fcd
commit dc49cd769b
16 changed files with 83 additions and 59 deletions
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6
read-cache.c
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@ -66,7 +66,7 @@ static int ce_compare_data(struct cache_entry *ce, struct stat *st)
return match;
}
static int ce_compare_link(struct cache_entry *ce, unsigned long expected_size)
static int ce_compare_link(struct cache_entry *ce, size_t expected_size)
{
int match = -1;
char *target;
@ -101,7 +101,7 @@ static int ce_modified_check_fs(struct cache_entry *ce, struct stat *st)
return DATA_CHANGED;
break;
case S_IFLNK:
if (ce_compare_link(ce, st->st_size))
if (ce_compare_link(ce, xsize_t(st->st_size)))
return DATA_CHANGED;
break;
default:
@ -797,7 +797,7 @@ int read_cache_from(const char *path)
}
if (!fstat(fd, &st)) {
cache_mmap_size = st.st_size;
cache_mmap_size = xsize_t(st.st_size);
errno = EINVAL;
if (cache_mmap_size >= sizeof(struct cache_header) + 20)
cache_mmap = xmmap(NULL, cache_mmap_size, PROT_READ | PROT_WRITE, MAP_PRIVATE, fd, 0);