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    <p>Some ARM processors have hardware floating-point, and some don't, so it's possible that this function is being compiled for hardware floating-point but your platform lacks a floating-point unit, so the floating-point instructions cause the processor to report an illegal instruction. If this is the first floating-point computation in your test program, that's extremely likely to be the problem. Check your platform's documentation to find which -march option you need to pass to gcc, or look at the compilation options used by some program that already works.</p> <p>This function does not have defined behaviour, and without an indication of what the desired behaviour is it's hard to suggest an improvement. Try something like this for a start:-</p> <pre><code>void convertFloatToFixed(float nX, float nY, unsigned int &amp;nFixed) { assert(nX * 32 &lt; INT_MAX); assert(nY * 32 &lt; INT_MAX); int sx = nX * 32; int sy = nY * 32; unsigned int ux = sx; unsigned int uy = sy; nFixed = (ux &lt;&lt; 16) | uy; } </code></pre> <p>I've got rid of the pointer casts, which (as others have pointed out) break the strict aliasing rule. I've also used <code>int</code> instead of <code>short</code>. There's generally no point having <code>short</code> auto variables, since they're widened to <code>int</code>s before computations anyway. (It's a good job they are, as shifting a <code>short</code> by 16 bits would not be very useful.) I've added some checks so your debug builds can find out if the float-to-integer conversion will overflow, which causes undefined behaviour.</p>
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    1. POGetting SIGILL in float to fixed conversion
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    1. USDan Hulme
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    1. POGetting SIGILL in float to fixed conversion
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    1. COI will accept your answer in the basis that the problem as related with the lack of a floating-point unit on the system I was testing with at the time (almost 2 years ago)
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