stm8 long integer assignment failure

仙景

stm8 long integer assignment failure [Copy link]

I'm working on a project recently, using stm8, and the compilation environment is stvd There is no problem reading and writing IDs, but when I assign an unsigned char array to a u32 bit, from 16 bits to 31 bits, it's either ffff or not displayed. Is it a compiler problem or something else?

lcofjp

It's a data type problem. The int type of your 8-bit compiler is generally 16 bits, and literals are also int unless otherwise specified. So the result of an expression like

1. pubf[2]<<16;

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is still int, which is 16 bits. It is obviously an overflow, so when 16-bit data is assigned to a 32-bit data type, the upper 16 bits cannot pass. Therefore, you need to convert the data type to make the subsequent calculation result 32 bits. So in the above expression, you only need to convert one of the operands to long. The simple way is to add an L after 16 to convert 16 to a long type literal. In this way, the calculation result of the two operands is long:

1. pubf[2]<<16L;

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lcofjp

It seems that unsigned long is better, so it should be

1. pubf[2]<<16UL;

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or

1. (unsigned long)pubf[2]<<16;

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仙景

lcofjp posted on 2017-1-19 11:48 It's a data type issue. Your 8-bit compiler's int type is usually 16 bits, and literals are also ints unless otherwise specified, so this expression has to...

Adding an L at the end doesn't work, and the result is the same. Adding a strong at the front doesn't work either.

lcofjp

仙景发表于2017-1-19 12:00 Adding L at the end doesn't work either, the result is the same. Adding L at the front doesn't work either.

I don't believe it... Rebuild and debug again, unless the compiler has a bug, if that doesn't work, adjust the assembly code

仙景

lcofjp posted on 2017-1-19 12:02 I don't believe it... rebuild and debug again, unless there is a bug in the compiler, if it doesn't work, you can adjust the assembly code

It doesn't work. I also thought it was a type alignment problem at first. It didn't work even after adding it. I tried everything. Just think it's a problem with the compiler.

lruifoot

It is not a compiler problem. Bit operations should pay attention to the CPU word length.

13266529715

It is clearly a problem of code writing: the following pbuf[x]<

stm8 long integer assignment failure