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A new Bug

unsigned char aa,bb,cc,dd;

aa = 0xab;
bb = 0xcd;
cc = (aa+bb)%255; //aa+bb=0x178
dd = (unsigned char)((aa+bb)%255);

when debug, youcan see that the result: cc is 0x78, dd is 0x79. In fact, cc and dd should be 0x79.

I debugged in C51 9.60, 9.03. Both had the same output.

I tried in VC2010, TI CCS3.3, both can get the correct result, 0x79.

Parents
  • Thank  you for your reply.

    My code uses parentheses to clearly indicate the operation priority, that is, first operate "aa + bb", then operate modulus 255, and then convert to "unsigned char"。The two lines of code differ only in the last step, I think their output should be the same in this operation as above。

Reply
  • Thank  you for your reply.

    My code uses parentheses to clearly indicate the operation priority, that is, first operate "aa + bb", then operate modulus 255, and then convert to "unsigned char"。The two lines of code differ only in the last step, I think their output should be the same in this operation as above。

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