From Bugzilla Helper: User-Agent: Mozilla/5.0 (X11; U; Linux x86_64; en-US; rv:1.7.3) Gecko/20040913 Description of problem: On AMD64: after a fesetround(FE_UPWARD) (ISO C99 standard function for changing IEEE arithmetics rounding mode to round-to-plus-infinity, i.e. round to the nearest greater or equal representable value), pow() on certain operands will result in a segmentation fault, and exp() on some operands will yield negative results (the exponential of a real number is never negative). Version-Release number of selected component (if applicable): 2.3.3 How reproducible: Always Steps to Reproduce: 1) x=79.252413924118542354335659183561801910400390625, y=0.333333299999999999041477849459624849259853363037109375 2) fesetround(FE_UPWARD); 3a) pow(x, y) 3b) exp(log(x)*y) (see attachment) Actual Results: 3a) Segmentation fault. 3b) result = -0.246008 Expected Results: Both programs should have given something around 4.295405, as it happens on IA32. Additional info: The glibc code (e_pow.c) that is used for some computations states, in a comment: "Assumption: Machine arithmetic operations are performed in round to nearest mode of IEEE 754 standard." The bug has been filed in glibc bugzilla (http://sources.redhat.com/bugzilla/show_bug.cgi?id=763). This bug has resulted in annoying crashes in scientific code doing interval arithmetic.
Created attachment 111517 [details] first example (pow() crash)
Created attachment 111518 [details] exp() yields negative result
There is no reason to duplicate the report here. FYI, #1 certainly doesn't crash for me and #2 doesn't yield negative value. This is with glibc-2.3.4-2.fc3.x86_64.rpm. It doesn't yield 4.2954 though, but 8.02056.
The first definitely crashes on FC2. What does pow(x,y) give on FC3/x86_64? (Note: exp() giving 8 instead of 4.2 seems like a wild result too...)