Hi/2.
Reimar Döffinger wrote:
> Hello,
> I do very much dislike just globally using "#pragma pack", use
> __attribute__((packed)) on a per-struct basis or even better
> avoid it completely, e.g. by using uint8_t buffers and bit
> functions and AV_RL*. Or find a system header where they are defined.
>
>
On OS/2, DosDevIOCtl() expect a packed struct or a byte buffer. So I
decide to use '#pragma pack' globally because all structs are for
DosDevIOCtl() except 'mp_vcd_priv_t'. And the system headers for them do
not exist.
>> +int vcd_seek_to_track(mp_vcd_priv_t *vcd, int track)
>> +{
>> + struct {
>> + UCHAR auchSign[4];
>> + BYTE bTrack;
>> + } sParam = {{'C', 'D', '0', '1'},};
>> +
>> + struct {
>> + msf msfStart;
>> + BYTE bAdr : 4;
>> + BYTE bControl : 4;
>> + } sData;
>>
>
> E.g. using those structs, unless they are defined in some system header
> is not better than using
> static const char sParam[5] = "CD01";
> uint8_t sData[5];
> Actually this is even more portable, since you do not rely on things
> like bitfield order, support for packed structs etc.
> This applies to all structs you defined, though a struct with only
> uint8_t elements and no bitfields instead of an array is ok (and
> possibly better for readability).
>
>
I'm confused. Are you commenting on my patches or saying your opinion
about 'structure' ?
Of course, I absolutely agree with you if these codes are for general
platforms and OSes. But these are only for OS/2. And those structs are
defined in according to OS/2 API DOCs. Why should I consider what you said ?
And I don't understand a byte buffer has a better readability than a
structure. If not using a structure, how can I know the meaning of each
index ?
And just a question. Is there a compiler not supporting 'packed structure' ?
>> + struct {
>> + BYTE abSync[12];
>> + BYTE abHeader[4];
>> + BYTE abSubHeader[8];
>> + BYTE abData[2324];
>> + BYTE abSpare[4];
>> + } sData;
>>
>
> I think the default stack size on OS/2 is rather small, so IMO you
> should not allocate more than 2kB on the stack if it can be avoided.
>
>
Yes, many compiler set the default stack size for OS/2 to 32K or 64K.
But I think that size is enough to use 2K stack variable. In addition,
GCC 4.3.2 are being ported to OS/2. It set the default stack size to 1M.
Currently I'm using that GCC 4.3.2. Nevertheless I'm setting the stack
size to 16M for MPlayer. So I think your apprehension is unnecessary.
--
KO Myung-Hun
Using Mozilla SeaMonkey 1.1.14
Under OS/2 Warp 4 for Korean with FixPak #15
On AMD ThunderBird 1 GHz with 512 MB RAM
Korean OS/2 User Community : http://www.ecomstation.co.kr