About the 31 bit issue, there's a chance the issue is that the asm.js FFI
boundary is treated as signed (an asm.js function returning a 32-bit
integer will use | 0). In that case, what might be the bug is that when JS
calls a function returning an unsigned value it should use >>> 0. Another
possibility is that the loads/stores of that struct value (makeSetValue
etc.) may need to be marked as unsigned.
On Sun, Mar 4, 2018 at 10:55 AM, Alon Zakai <alonza...@gmail.com> wrote:
> 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 <soe...@zfaas.com> 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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