jjc@jclark.UUCP (James Clark) (07/14/90)
There is an interesting bug in cfront 2.0 that arises only when it is used with an ANSI C compiler such as gcc. In this program #define INT_MAX 2147483647 #define INT_MIN (-INT_MAX-1) int foo(int n) { return n >= INT_MIN; } #include <stdio.h> int main() { printf("foo(0) returns %d\n", foo(0)); return 0; } cfront translates foo() into: int foo__Fi(__0n) int __0n; { return (__0n >= -2147483648); } ANSI C says that the type of 2147483648 (on a machine with 32 bit two's complement ints) is unsigned because it's > INT_MAX. The fact that it's negated doesn't change this. So the expression ends up being evaluated using unsigned arithmetic which of course gives the wrong answer. This problem doesn't show up using traditional C compilers because they give 2147483648 a signed type. This bug can be worked around by casting INT_MIN to long. James Clark jjc@jclark.uucp jjc@ai.mit.edu