Re: value of the constant expression 1<<(1?1:1) < 0x9999

Francois Grieu wrote:
Hello,

one of my C compiler (Keil C51) evaluates the constant expression
1<<(1?1:1) < 0x9999
to the value 1.

Correct...

1 << (1?1:1) < 0x9999
(1 << (1?1:1)) < 0x9999
(1 << 1) < 0x9999
2 < 0x9999
1

// this returns 0, much to my surprise
unsigned char bug4_a(void)
{
return 1<<(1?1:1) < 0x9999;
}

Can this find a satisfactory explanation under some definition of the
C language ?

No.

Note: I still get 0 for

return 1<<(1?1:1) < (unsigned)0x9999;

return 1<<(unsigned char)(1?1:1) < 0x9999;

Integer promotion must be applied, but it is incidental. They
should all return 1 on a conforming implementation.

--
Peter
.

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