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60 lines
1.6 KiB
C
60 lines
1.6 KiB
C
/*
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!!DESCRIPTION!! equality problem
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!!ORIGIN!! Testsuite
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!!LICENCE!! Public Domain
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*/
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/*
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Different results, depending on whether constant is on left or right side.
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The optimizer sometimes makes code that executes the right-side expression
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as eight bits; but then, tests it against the left-side zero as 16 bits.
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The high-byte is garbage; therefore, that test might, or might not, work.
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It depends on the platform and the amount of optimization.
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http://www.cc65.org/mailarchive/2014-10/11680.html
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http://www.cc65.org/mailarchive/2014-10/11682.html
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http://www.cc65.org/mailarchive/2014-10/11683.html
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*/
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#include <stdio.h>
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static unsigned char fails = 4;
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static unsigned char bad[3], good[3];
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int main(void)
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{
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unsigned char joy_state = 0x7e;
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unsigned a, b;
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/* NOTE: It fails in only the printf() statements, the other stuff
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below works! */
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printf("bad: %u, ", 0 == (joy_state & 1) );
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printf("good: %u\n", (joy_state & 1) == 0 );
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sprintf(bad, "%u", 0 == (joy_state & 1) );
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sprintf(good, "%u", (joy_state & 1) == 0 );
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printf("bad: %u, ", bad[0] - '0' );
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printf("good: %u\n", good[0] - '0' );
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fails -= bad[0] - '0';
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fails -= good[0] - '0';
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if (0 == (joy_state & 1)) fails--;
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if ((joy_state & 1) == 0) fails--;
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printf("failures: %u\n", fails );
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/* The above printf() returns a value with a zero high-byte.
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** Therefore, the next (broken) statement works (by accident).
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*/
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a = 0 == (joy_state & 1);
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b = (joy_state & 1) == 0;
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printf("a: %u, ", a );
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printf("b: %u\n", b );
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return fails;
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}
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