[FFmpeg-devel] [PATCH] examples/decoding_encoding: remove unused variable "size"

[François Revol]

On 12/04/2012 11:11, Clément Bœsch wrote:
> On Thu, Apr 12, 2012 at 10:14:30AM +0200, Nicolas George wrote:
>> Le quartidi 24 germinal, an CCXX, Clément Bœsch a écrit :
>>> Note: am I the only one to require an extra LDFLAGS=-lm to link this
>>> example?
>>
>> Works for me. How do you try to link it exactly?
>>
> 
> [~/ffmpeg/doc/examples]% make decoding_encoding
> cc decoding_encoding.o -lavdevice -lavformat -lavfilter -lavcodec -lswscale -lavutil   -o decoding_encoding
> /usr/bin/ld: decoding_encoding.o: undefined reference to symbol 'sin@@GLIBC_2.2.5'
> /usr/bin/ld: note: 'sin@@GLIBC_2.2.5' is defined in DSO /lib/libm.so.6 so try adding it to the linker command line
> /lib/libm.so.6: could not read symbols: Invalid operation
> collect2: error: ld returned 1 exit status
> make: *** [decoding_encoding] Error 1
> 
> [~/ffmpeg/doc/examples]% LDFLAGS=-lm make decoding_encoding
> cc decoding_encoding.o -lm -lavdevice -lavformat -lavfilter -lavcodec -lswscale -lavutil   -o decoding_encoding
> 
> The libav* link against libm, but it works only for internal usage:
> 
> 95:            samples[2*j] = (int)(sin(t) * 10000);
> 
> This requires to link against -lm explicitely I guess (this is also true for
> the muxing example).
> 
> And BTW, about that Makefile, I think LDLIBS would more appropriate that
> LDFLAGS.
> 

Note libm does not exist everywhere, so do not hardcode it.
configure should already detect it, you just need to add the correct
variable to the LDFLAGS.

François.