[FFmpeg-devel] [PATCH] Work around msvc (c99wrap) build failure

[Michael Niedermayer]

On Sun, Aug 25, 2013 at 09:57:45PM -0600, Pavel Koshevoy wrote:
> On 8/25/13 9:13 PM, Michael Niedermayer wrote:
> >On Sun, Aug 25, 2013 at 06:30:35PM -0600, pkoshevoy at gmail.com wrote:
> >>From: Pavel Koshevoy <pkoshevoy at gmail.com>
> >>
> >>c99wrap choked on initialization of .dbl start_time option with
> >>AV_NOPTS_VALUE: Unable to parse int64_t as expression primary
> >>
> >>Signed-off-by: Pavel Koshevoy <pkoshevoy at gmail.com>
> >>---
> >>  libavfilter/vf_fps.c |    6 ++++--
> >>  1 file changed, 4 insertions(+), 2 deletions(-)
> >>
> >>diff --git a/libavfilter/vf_fps.c b/libavfilter/vf_fps.c
> >>index e30e90b..219bcd1 100644
> >>--- a/libavfilter/vf_fps.c
> >>+++ b/libavfilter/vf_fps.c
> >>@@ -25,6 +25,8 @@
> >>   * a filter enforcing given constant framerate
> >>   */
> >>+#include <float.h>
> >>+
> >>  #include "libavutil/common.h"
> >>  #include "libavutil/fifo.h"
> >>  #include "libavutil/mathematics.h"
> >>@@ -61,7 +63,7 @@ typedef struct FPSContext {
> >>  #define F AV_OPT_FLAG_FILTERING_PARAM
> >>  static const AVOption fps_options[] = {
> >>      { "fps", "A string describing desired output framerate", OFFSET(framerate), AV_OPT_TYPE_VIDEO_RATE, { .str = "25" }, .flags = V|F },
> >>-    { "start_time", "Assume the first PTS should be this value.", OFFSET(start_time), AV_OPT_TYPE_DOUBLE, { .dbl = AV_NOPTS_VALUE}, INT64_MIN, INT64_MAX, V },
> >>+    { "start_time", "Assume the first PTS should be this value.", OFFSET(start_time), AV_OPT_TYPE_DOUBLE, { .dbl = DBL_MAX }, -DBL_MAX, DBL_MAX, V },
> >does INT64_MIN work as well ?
> >if so i think its preferable as it has the same nummeric value as
> >AV_NOPTS_VALUE, introducing no change except the fix/workaround
> >(vf_fps.c could check by assert that the 2 match)
> >
> 
> No, INT64_MIN triggers the same error from c99wrap: Unable to parse
> int64_t as expression primary
> 
> I suspect c99wrap chokes on the typecast statement.
> 
> If I change it to { .dbl = 0 } it compiles fine.
> If I change it to { .dbl = (double)0 } it complains:  Unable to
> parse double as expression primary

next try:
-9223372036854775808.0


> 
> I don't see why there is any particular attachment to AV_NOPTS_VALUE
> as initial value for start_time.  It's appears to be just that -- an

its the "not set" value throughout the codebase, also some user
app could be setting that intentionally or unintenionally


> initial value used to determine whether a user has actually set a
> start_time value.  The initial value can be any reasonably
> exceptional value, maybe even a NAN.  Although, I am not sure how
> well NAN would work with min/max constraints.
> 
>     Pavel.
> 
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-- 
Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

Let us carefully observe those good qualities wherein our enemies excel us
and endeavor to excel them, by avoiding what is faulty, and imitating what
is excellent in them. -- Plutarch
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