[FFmpeg-devel] [PATCH] compilation error in libavcodec/x86/mpegaudiodsp.c

[Derek Buitenhuis]

On 5/5/2014 12:42 PM, Paweł Witas wrote:
> +#if HAVE_AVX_EXTERNAL
>       if (EXTERNAL_AVX(cpu_flags)) {
>           s->imdct36_blocks_float = imdct36_blocks_avx;
>       }
> +#endif

I am incline not to accept this. This is a hack to fix improper DCE.

> I use MinGW/MSys tools.
> My ffmpeg compilation configuration for Pentium III and above, that causes this error:
> 
> ./configure --toolchain=msvc --prefix=/usr/local \
>   --extra-cflags="-arch:SSE -O2 -MT -LD -I/usr/local/include -D_BIND_TO_CURRENT_CRT_VERSION=1 -D_BIND_TO_CURRENT_MFC_VERSION=1" \
>   --arch=x86 --cpu=c3-2 --disable-runtime-cpudetect --disable-sse2 --disable-sse3 --disable-ssse3 --disable-sse4 --disable-sse42 \
>   --disable-amd3dnow --disable-amd3dnowext --disable-avx --disable-avx2 --disable-xop --disable-fma3 --disable-fma4 \
>   --disable-gpl --disable-debug --enable-shared --enable-swscale \
>   --disable-decoder=aac --disable-encoder=aac --enable-decoder=aac_latm \
>   --enable-libfdk-aac --disable-libaacplus --enable-nonfree

Let's break this down, as it seems you do not know what you are doing.

> --extra-cflags="-arch:SSE -O2 -MT -LD -I/usr/local/include -D_BIND_TO_CURRENT_CRT_VERSION=1 -D_BIND_TO_CURRENT_MFC_VERSION=1"

This makes no sense. Also, please try a build without all the custom flags.

In order:

> -arch:SSE

All recent MSVC compiles default to SSE (SSE2 even I think). This is superfluous.

> -O2 -MT

All of these are default for FFmpeg. Why are you specifying them twice?

> -LD

Incorrect. If you want DLLs, use --enable-shared alone.

> -I/usr/local/include

Very wrong. Do NOT pass MSVC your *MinGW* includes folder.

>  -D_BIND_TO_CURRENT_CRT_VERSION=1 -D_BIND_TO_CURRENT_MFC_VERSION=1

Why?

> --cpu=c3-2

Welcome to 15 years ago I guess.

> --disable-runtime-cpudetect

This is the exact opposite of what you want. You *want* it to see what the CPU
can do at runtime, and in fact this is pretty much the only way we support nowadays.

> --disable-sse2 --disable-sse3 --disable-ssse3 --disable-sse4 --disable-sse42 \
>   --disable-amd3dnow --disable-amd3dnowext --disable-avx --disable-avx2 --disable-xop --disable-fma3 --disable-fma4

Do not do this. You are crippling the build. The binary will run perfectly fine on a P3,
since we detect the CPU capabilities at runtime.

> --disable-gpl

Pointless. LGPL is default.

> --enable-swscale

Pointless. It is enabled by default.

> --enable-decoder=aac_latm

Ditto.

> --disable-libaacplus 

Pointless, as you have to explicitly enable this.

After trying a build with default settings, please tell us your compiler
version.

- Derek