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Tracktion / choc

A collection of header only classes, permissively licensed, to provide basic useful tasks with the bare-minimum of dependencies.

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emcc and inline assembly issue

davebang opened this issue · comments

commented

Trying to #include <choc/audio/choc_AudioFileFormat_FLAC.h> and compile with emcc but it doesn't like this inline asm....

subprojects/choc/audio/choc_AudioFileFormat_FLAC.h:6702:46: error: invalid output constraint '=a' in asm
    asm volatile (".byte 0x0f, 0x01, 0xd0" : "=a"(lo), "=d"(hi) : "c" (0));
                                             ^
1 error generated.

Have worked around it by undefining the __GNUC__ macro that encapsulates this code temporarily. Was hoping to define FLAC__NO_ASM as a fix but that doesn't seem to cover it. Not sure if there's something I'm missing here but it seems like there maybe should be provision for emcc to avoid this line and fallthrough to the return 0 in the #else case below?

commented

Hmm, thanks for the heads-up, I've not been testing emcc as a target, though it'd certainly be good to support it. I'm sure I can fudge some macros to avoid it hitting that codepath...

commented

..does it work for you if you just bang a check for CHOC_EMSCRIPTEN at the end of line 173?

#if ! (defined (__ARM_ARCH) || defined (__arm__) || defined (__arm64__) || defined(__aarch64__) || defined(_M_ARM64) || CHOC_EMSCRIPTEN)
commented

Thanks! Yes, I need to add -DCHOC_EMSCRIPTEN to emcc too but then it works

commented

CHOC_EMSCRIPTEN isn't supposed to be added to a build, it's automatically detected in choc_Platform.h

Maybe we need to make sure choc_Platform.h is included at the top of that file?

commented

..or simpler, just use this:

#if ! (defined (__ARM_ARCH) || defined (__arm__) || defined (__arm64__) || defined(__aarch64__) || defined(_M_ARM64) || defined (__EMSCRIPTEN__))
commented

Brilliant - yes, that's got it. I was getting "Unknown platform" when including the platform header.

But adding defined (__EMSCRIPTEN__) alone works great.

commented

Cool, I'll push that change. Is that the only problem you've hit with emcc?

commented

So far yes but it's the first time I've built a class that includes choc with emcc. I'm going to be doing more, so will let you know if I run in to anything else.

commented

@julianstorer quick follow up, whilst i managed to resolve the emcc compiler issues, I never actually managed to access/playback the audio. It was a little while ago now but IIRC, it was some problem at AudioFileReader readEntireStream(). Perhaps the buffer was empty or some runtime issue, I can't remember exactly. We switched to the WAV reader for the short-term and all is fine.

I investigated a little but other tasks took priority so I never got to the bottom of it. I'll follow up again if/when I revisit it.