It comes that time again when I try and get my PC build working on Android via Android Studio. All was going swimmingly, it ran in the emulator fine, but on my first actual test device (Google Nexus 7 2012 tablet (32 bit ARM Cortex-A9, ARM v7A architecture)) I was getting a 'SIGBUS illegal alignment' crash.
My little research has indicated that while x86 is fine with loading 16 / 32 / 64 bit values from any byte address in memory, the earlier ARM chips may need data to be aligned to the data size. This isn't a massive problem, and I see the reason for it (probably faster, like SIMD aligned loads, and simpler for the CPU). I probably have quite a few of these, particular in my own byte packed file formats. I can adjust the exporter / formats so that they are using the required alignment.
Just to confirm, if anyone knows this, is it all 16 / 32 / 64 bit accesses that need to be data size aligned on early android devices? Or e.g. just 64 bit size access?
And is there any easy way to get the compiler to spit out some kind of useful information as to the alignment of each member of a struct / class, so I can quickly pin down the culprits?
The ARM docs (http://infocenter.arm.com/help/index.jsp?topic=/com.arm.doc.faqs/ka15414.html) suggest another alternative is using a __packed qualifier. Anyone used this, is this practical?
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