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// Example code from the user manual
import org.checkerframework.checker.signedness.qual.Unsigned;
public class SignednessManualExample {
int s1 = -2;
int s2 = -1;
@Unsigned int u1 = 2147483646; // unsigned: 2^32 - 2, signed: -2
@Unsigned int u2 = 2147483647; // unsigned: 2^32 - 1, signed: -1
void m() {
int w = s1 / s2; // OK: result is 2, which is correct for -2 / -1
// :: error: (operation.unsignedlhs)
int x = u1 / u2; // ERROR: result is 2, which is incorrect for (2^32 - 2) / (2^32 - 1)
}
int s3 = -1;
int s4 = 5;
@Unsigned int u3 = 2147483647; // unsigned: 2^32 - 1, signed: -1
@Unsigned int u4 = 5;
void m2() {
int y = s3 % s4; // OK: result is -1, which is correct for -1 % 5
// :: error: (operation.unsignedlhs)
int z = u3 % u4; // ERROR: result is -1, which is incorrect for (2^32 - 1) % 5 = 2
}
void useLocalVariables() {
int s1 = -2;
int s2 = -1;
@Unsigned int u1 = 2147483646; // unsigned: 2^32 - 2, signed: -2
@Unsigned int u2 = 2147483647; // unsigned: 2^32 - 1, signed: -1
int w = s1 / s2; // OK: result is 2, which is correct for -2 / -1
int x = u1 / u2; // OK; computation over constants, interpreted as signed; result is signed
int s3 = -1;
int s4 = 5;
@Unsigned int u3 = 2147483647; // unsigned: 2^32 - 1, signed: -1
@Unsigned int u4 = 5;
int y = s3 % s4; // OK: result is -1, which is correct for -1 % 5
int z = u3 % u4; // OK; computation over constants, interpreted as signed; result is signed
}
}
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