potential bugs?

[dongyuma]

Hello, my research group is developing a symbolic execution tool called YUSE to detect floating-point exceptions in numerical code. We've found inputs that cause some of the GSL 2.7.1 functions to throw floating-point exceptions. I've written this mail to see if you consider any of them (8 results) to be real bugs. If you could confirm whether any of these exceptions are useful or actual warnings, we would very appreciate it.

The purpose of our tool is to comprehensively detect floating-point exceptions in the program. For each category of floating-point exception we found, we listed 1 or 2. We describe the name of function, the type of exception thrown, the inputs that trigger the exception, and specific location of the code that causes the exception.

Category 1：invalid operation exception
1.The function gsl_sf_conicalP_xlt1_large_neg_mu_e throws an invalid exception when its input tau=1.0, mu=2.0, x=3.0 at line 221 in file /gsl-2.7.1/specfunc/legendre_con.c: double p = x/sqrt(beta2*(1.0-xx) + 1.0); Because the parameter of sqrt cannot be negative numbers, invalid exception occurs in this occasion.
2.The function gsl_cdf_laplace_Qinv throws an invalid exception when its input Q=-0.5 at line 67 in file /gsl-2.7.1/cdf/laplaceinv.c：x = -a * log(2Q);Because the parameter of log cannot be negative numbers, invalid exception occurs in this occasion.

Category 2：overflow
3.The function gsl_sf_bessel_Knu_scaled_asymp_unif_e throws a overflow exception when its input nu=1.45e-192, x=1.0 at line 398 in file /gsl-2.7.1/specfunc/bessel.c: double root_term = hypot(1.0,z);
4.The function gsl_sf_conicalP_xlt1_large_neg_mu_e throws a overflow exception when its input tau =1.23e189,mu=1e-2 at line 219 in file /gsl-2.7.1/specfunc/legendre_con.c: double beta2 = beta*beta;

Category 3：underflow
5.The function gsl_sf_bessel_Jnu_asympx_e throws an underflow exception when its input nu=1.23e-189, x=1.0 at line 217 in file /gsl-2.7.1/specfunc/bessel.c: double mu = 4.0nunu;

Category 4：division-by-zero
6.The function gsl_sf_bessel_Knu_scaled_asympx_e throws an division-by-zero floating-point exception when its input x=0.0 at line 318 in file /gsl-2.7.1/specfunc/bessel.c: double r = nu/x;

Category 5：type conversion
7.The function gsl_ran_gamma_knuth throws an overflow caused by type conversion exception when its input a=1.23e189 at line 44 in file /gsl-2.7.1/randist/gamma.c: unsigned int na = floor (a);

Category 6：inexact(rounding error)
8.The function hyperg_1F1_1 throws a rounding error exception which cause the while loop to not terminate when its input b=x=1.23e189 at line 378 in file /gsl-2.7.1/specfunc/hyperg_1F1.c: while(bp > b+0.1) {.The loop at 378 will not terminate when x reaches 1.23e189 (a very large value),because bp -= 1.0 at line 380 makes bp – 1.0 is rounded to bp itself, thus the while condition at bp > b+0.1 at 378 is satisfied all the time and can not terminate.

For the 8 scenarios listed above, I think whether it would be better to do some check on the variable's(parameter’s) scope in advance when calling the function. If not, it would be dangerous according to invalid inputs and there will be problems where return values from the above questions are used. (For example, before calling the sqrt(x) function, put if(x<0){return;} in order to check, and so on.)

I am very sorry about that I have disturbed you in your busy schedule. If anyone could confirm whether any of these exceptions is actual, I would appreciate it. I am looking forward to your reply. Thank you very much.