[FFmpeg-devel] [PATCHv2] all: fix enum definition for large values
Ronald S. Bultje
rsbultje at gmail.com
Wed Oct 28 16:38:14 CET 2015
Hi,
On Wed, Oct 28, 2015 at 11:00 AM, Ganesh Ajjanagadde <gajjanagadde at gmail.com
> wrote:
> On Wed, Oct 28, 2015 at 10:53 AM, Ronald S. Bultje <rsbultje at gmail.com>
> wrote:
> > Hi,
> >
> > On Wed, Oct 28, 2015 at 10:48 AM, Ganesh Ajjanagadde
> > <gajjanagadde at gmail.com> wrote:
> >>
> >> On Wed, Oct 28, 2015 at 10:34 AM, Ronald S. Bultje <rsbultje at gmail.com>
> >> wrote:
> >> > Hi,
> >> >
> >> > On Wed, Oct 28, 2015 at 8:20 AM, Ganesh Ajjanagadde
> >> > <gajjanagadde at gmail.com>
> >> > wrote:
> >> >>
> >> >> On Wed, Oct 28, 2015 at 7:00 AM, Ronald S. Bultje <
> rsbultje at gmail.com>
> >> >> wrote:
> >> >> > Hi,
> >> >> >
> >> >> > On Tue, Oct 27, 2015 at 10:58 PM, Ganesh Ajjanagadde
> >> >> > <gajjanagadde at gmail.com> wrote:
> >> >> >>
> >> >> >> On Tue, Oct 27, 2015 at 10:41 PM, Ronald S. Bultje
> >> >> >> <rsbultje at gmail.com>
> >> >> >> wrote:
> >> >> >> > Hi,
> >> >> >> >
> >> >> >> > On Tue, Oct 27, 2015 at 8:53 PM, Ganesh Ajjanagadde
> >> >> >> > <gajjanagadde at gmail.com>
> >> >> >> > wrote:
> >> >> >> >>
> >> >> >> >> ISO C restricts enumerator values to the range of int. Thus
> (for
> >> >> >> >> instance)
> >> >> >> >> 0x80000000
> >> >> >> >> unfortunately does not work, and throws a warning with
> -Wpedantic
> >> >> >> >> on
> >> >> >> >> clang 3.7.
> >> >> >> >>
> >> >> >> >> This fixes it by using alternative expressions that result in
> >> >> >> >> identical
> >> >> >> >> values but do not have this issue.
> >> >> >> >>
> >> >> >> >> Tested with FATE.
> >> >> >> >>
> >> >> >> >> Signed-off-by: Ganesh Ajjanagadde <gajjanagadde at gmail.com>
> >> >> >> >> ---
> >> >> >> >> libavcodec/dca_syncwords.h | 26 ++++++++++++--------------
> >> >> >> >> libavformat/cinedec.c | 2 +-
> >> >> >> >> libavformat/mov_chan.c | 2 +-
> >> >> >> >> 3 files changed, 14 insertions(+), 16 deletions(-)
> >> >> >> >>
> >> >> >> >> diff --git a/libavcodec/dca_syncwords.h
> >> >> >> >> b/libavcodec/dca_syncwords.h
> >> >> >> >> index 3466b6b..6981cb8 100644
> >> >> >> >> --- a/libavcodec/dca_syncwords.h
> >> >> >> >> +++ b/libavcodec/dca_syncwords.h
> >> >> >> >> @@ -19,19 +19,17 @@
> >> >> >> >> #ifndef AVCODEC_DCA_SYNCWORDS_H
> >> >> >> >> #define AVCODEC_DCA_SYNCWORDS_H
> >> >> >> >>
> >> >> >> >> -enum DCASyncwords {
> >> >> >> >> - DCA_SYNCWORD_CORE_BE = 0x7FFE8001U,
> >> >> >> >> - DCA_SYNCWORD_CORE_LE = 0xFE7F0180U,
> >> >> >> >> - DCA_SYNCWORD_CORE_14B_BE = 0x1FFFE800U,
> >> >> >> >> - DCA_SYNCWORD_CORE_14B_LE = 0xFF1F00E8U,
> >> >> >> >> - DCA_SYNCWORD_XCH = 0x5A5A5A5AU,
> >> >> >> >> - DCA_SYNCWORD_XXCH = 0x47004A03U,
> >> >> >> >> - DCA_SYNCWORD_X96 = 0x1D95F262U,
> >> >> >> >> - DCA_SYNCWORD_XBR = 0x655E315EU,
> >> >> >> >> - DCA_SYNCWORD_LBR = 0x0A801921U,
> >> >> >> >> - DCA_SYNCWORD_XLL = 0x41A29547U,
> >> >> >> >> - DCA_SYNCWORD_SUBSTREAM = 0x64582025U,
> >> >> >> >> - DCA_SYNCWORD_SUBSTREAM_CORE = 0x02B09261U,
> >> >> >> >> -};
> >> >> >> >> +#define DCA_SYNCWORD_CORE_BE 0x7FFE8001U
> >> >> >> >> +#define DCA_SYNCWORD_CORE_LE 0xFE7F0180U
> >> >> >> >> +#define DCA_SYNCWORD_CORE_14B_BE 0x1FFFE800U
> >> >> >> >> +#define DCA_SYNCWORD_CORE_14B_LE 0xFF1F00E8U
> >> >> >> >> +#define DCA_SYNCWORD_XCH 0x5A5A5A5AU
> >> >> >> >> +#define DCA_SYNCWORD_XXCH 0x47004A03U
> >> >> >> >> +#define DCA_SYNCWORD_X96 0x1D95F262U
> >> >> >> >> +#define DCA_SYNCWORD_XBR 0x655E315EU
> >> >> >> >> +#define DCA_SYNCWORD_LBR 0x0A801921U
> >> >> >> >> +#define DCA_SYNCWORD_XLL 0x41A29547U
> >> >> >> >> +#define DCA_SYNCWORD_SUBSTREAM 0x64582025U
> >> >> >> >> +#define DCA_SYNCWORD_SUBSTREAM_CORE 0x02B09261U
> >> >> >> >
> >> >> >> >
> >> >> >> > This one is fine.
> >> >> >> >
> >> >> >> >>
> >> >> >> >> --- a/libavformat/cinedec.c
> >> >> >> >> +++ b/libavformat/cinedec.c
> >> >> >> >> @@ -50,7 +50,7 @@ enum {
> >> >> >> >> CFA_BAYER = 3, /**< GB/RG */
> >> >> >> >> CFA_BAYERFLIP = 4, /**< RG/GB */
> >> >> >> >>
> >> >> >> >> - CFA_TLGRAY = 0x80000000,
> >> >> >> >> + CFA_TLGRAY = INT32_MIN,
> >> >> >> >> CFA_TRGRAY = 0x40000000,
> >> >> >> >> CFA_BLGRAY = 0x20000000,
> >> >> >> >> CFA_BRGRAY = 0x10000000
> >> >> >> >> diff --git a/libavformat/mov_chan.c b/libavformat/mov_chan.c
> >> >> >> >> index a2fa8d6..f6181e2 100644
> >> >> >> >> --- a/libavformat/mov_chan.c
> >> >> >> >> +++ b/libavformat/mov_chan.c
> >> >> >> >> @@ -45,7 +45,7 @@
> >> >> >> >> * do not specify a particular ordering of those
> >> >> >> >> channels."
> >> >> >> >> */
> >> >> >> >> enum MovChannelLayoutTag {
> >> >> >> >> - MOV_CH_LAYOUT_UNKNOWN = 0xFFFF0000,
> >> >> >> >> + MOV_CH_LAYOUT_UNKNOWN = -( 1 << 16),
> >> >> >> >> MOV_CH_LAYOUT_USE_DESCRIPTIONS = ( 0 << 16) | 0,
> >> >> >> >> MOV_CH_LAYOUT_USE_BITMAP = ( 1 << 16) | 0,
> >> >> >> >> MOV_CH_LAYOUT_DISCRETEINORDER = (147 << 16) | 0,
> >> >> >> >> --
> >> >> >> >> 2.6.2
> >> >> >> >
> >> >> >> >
> >> >> >> > I personally don't really like these... I think both obfuscate
> the
> >> >> >> > meaning
> >> >> >> > of the flag values, particularly the first one.
> >> >> >>
> >> >> >> There is no real solution (recall apedec and the INT32_MIN final
> >> >> >> solution), barring adding a comment signifying our intent (ie the
> >> >> >> desired hex mask). I can do this if you think it helps.
> >> >> >
> >> >> >
> >> >> > The solution is to not care about ISO C if it doesn't fix real
> >> >> > issues.
> >> >> > :)
> >> >>
> >> >> This is where we will just have to agree to disagree, I consider this
> >> >> issue "real enough" - it is a violation of the standard, and POSIX
> >> >> says nothing contrariwise unlike the function pointer/data pointer
> >> >> thing.
> >> >
> >> >
> >> > Well, that doesn't really help figuring out a way to do this in a way
> >> > that
> >> > we all find acceptable. So let's do that instead.
> >> >
> >> > For the enum movChannelLayoutTag, I don't think we ever rely on it
> being
> >> > an
> >> > enum do we? In fact, I'd say that the solution you used for the DCA
> >> > enums
> >> > (use macros instead of enums) would work here also.
> >>
> >> Well, there are some arrays defined in terms of this. The type of the
> >> array will need to be changed appropriately. I hence gave this as the
> >> solution producing the minimal diff while sticking to the standard.
> >> This one I thus strongly prefer keeping it as in the above patch.
> >
> >
> > Right, but it doesn't fix the issue. The individual bits of the value may
> > have the same value as currently and you're not causing that one compiler
> > warning. But you're still assigning a negative/signed value to a field
> that
> > is used as unsigned. See this piece of code:
> >
> > struct MovChannelLayoutMap {
> > uint32_t tag; << unsigned
> > uint64_t layout;
> > };
> >
> > static const struct MovChannelLayoutMap mov_ch_layout_map_misc[] = {
> > [..]
> > { MOV_CH_LAYOUT_UNKNOWN, 0 }, << assigning a
> signed/negative
> > value
>
> So what? This is completely portable, signed to unsigned conversion
> has well defined semantics (e.g
>
> https://stackoverflow.com/questions/50605/signed-to-unsigned-conversion-in-c-is-it-always-safe
> ),
> essentially guaranteeing identical bit patterns.
Then why "fix" the enum?
Ronald
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