C_STRUCTS is generated from the headers in gen_struct_info.py, basically by
compiling small C programs to see what the offsets are. I believe it does
not look at sizes, though (except for __size__ which is computed for the
entire struct). The numbers there are the offsets, not the sizes. So
st_size is at offset 36.
The stat.h says
off_t st_size;
blksize_t st_blksize;
I'm not sure how to easily find the definition of off_t, but looking in the
offsets, st_size is 36 and st_blksize which is after it is 40, so the size
must be 4. So it's not big enough if you need more then 32 bits, off_t
would need to be redefined. (Do you really need more than 32 bits, though?)
A separate question is if 32-bit values work - I think you said 31 bits
seems to be the limit. That could be due to treating the value as signed
somewhere ( | 0 will do that). If 32 unsigned bits are enough for you,
finding that bug might be practical.
On Sat, Mar 3, 2018 at 12:31 AM, Soeren Balko <[email protected]> wrote:
> In struct_info.compiled.json, the "stat" struct is declared like so:
>
> "stat":{
>
> "st_rdev":28,
> "st_mtim":{
> "tv_sec":56,
> "tv_nsec":60,
> "__size__":8
> },
> "st_blocks":44,
> "st_atim":{
> "tv_sec":48,
> "tv_nsec":52,
> "__size__":8
> },
> "st_nlink":16,
> "__st_ino_truncated":8,
> "st_ctim": {
>
> "tv_sec":64,
> "tv_nsec":68,
> "__size__":8
> },
> "st_mode":12,
> "st_blksize":40,
> "__st_dev_padding":4,
> "st_dev":0,
> "st_size":36,
> "st_gid":24,
> "__st_rdev_padding":32,
> "st_uid":20,
> "st_ino":72,
> "__size__":76
> }
>
>
> I assume the properties are the bit widths of the various fields (?).
> According to this, st_size is 36 bits, which is enough to cater even for
> very large files.
>
> Can you please confirm, Alon?
>
>
> On Saturday, March 3, 2018 at 6:18:09 PM UTC+10, Soeren Balko wrote:
>
>> Thanks, Alon! This does indeed seem to be the issue. In
>> library_syscall.js, the "st_size" member is considered am i32 (see below).
>> I do not yet fully understand how C_STRUCTS is generated. I can see that
>> compiler.js receives a JSON object STRUCT_INFO that contains the type
>> definitions. Is this generated from the musl headers?
>>
>> doStat: function(func, path, buf) {
>> try {
>> var stat = func(path);
>> } catch (e) {
>> if (e && e.node && PATH.normalize(path) !== PATH.normalize(FS.getPath(e.
>> node))) {
>> // an error occurred while trying to look up the path; we should just
>> report ENOTDIR
>> return -ERRNO_CODES.ENOTDIR;
>> }
>> throw e;
>> }
>> {{{ makeSetValue('buf', C_STRUCTS.stat.st_dev, 'stat.dev', 'i32') }}};
>> {{{ makeSetValue('buf', C_STRUCTS.stat.__st_dev_padding, '0', 'i32') }}};
>> {{{ makeSetValue('buf', C_STRUCTS.stat.__st_ino_truncated, 'stat.ino', '
>> i32') }}};
>> {{{ makeSetValue('buf', C_STRUCTS.stat.st_mode, 'stat.mode', 'i32') }}};
>> {{{ makeSetValue('buf', C_STRUCTS.stat.st_nlink, 'stat.nlink', 'i32')
>> }}};
>> {{{ makeSetValue('buf', C_STRUCTS.stat.st_uid, 'stat.uid', 'i32') }}};
>> {{{ makeSetValue('buf', C_STRUCTS.stat.st_gid, 'stat.gid', 'i32') }}};
>> {{{ makeSetValue('buf', C_STRUCTS.stat.st_rdev, 'stat.rdev', 'i32') }}};
>> {{{ makeSetValue('buf', C_STRUCTS.stat.__st_rdev_padding, '0', 'i32')
>> }}};
>> *{{{ makeSetValue('buf', C_STRUCTS.stat.st_size, 'stat.size', 'i32') }}};*
>> {{{ makeSetValue('buf', C_STRUCTS.stat.st_blksize, '4096', 'i32') }}};
>> {{{ makeSetValue('buf', C_STRUCTS.stat.st_blocks, 'stat.blocks', 'i32')
>> }}};
>> {{{ makeSetValue('buf', C_STRUCTS.stat.st_atim.tv_sec, '(stat.atime.getTime()
>> / 1000)|0', 'i32') }}};
>> {{{ makeSetValue('buf', C_STRUCTS.stat.st_atim.tv_nsec, '0', 'i32') }}};
>> {{{ makeSetValue('buf', C_STRUCTS.stat.st_mtim.tv_sec, '(stat.mtime.getTime()
>> / 1000)|0', 'i32') }}};
>> <td id="LC61" class="blob-code blob-code-inner js-file-line"
>> style="text-align: left; box-sizing: border-box; padding-right: 10px;
>> padding-lef
>>
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