------- Comment #5 from kargl at gcc dot gnu dot org 2007-11-28 00:06 ------- (In reply to comment #4) > (In reply to comment #3) > > (Admittedly from the 4.2.2 manual): > 2.2 Options controlling Fortran dialect > -frange-check > Enable range checking on results of simplification of constant expressions > during compilation. For example, by default, GNU Fortran will give an overflow > error at compile time when simplifying a = EXP(1000). With -fno-range-check, > no > error will be given and the variable a will be assigned the value +Infinity.
The documentation is wrong. Fortunately, I didn't write it. I do commend you on actually trying to use the documentation. > Referring to compiler output agreeing with itself is not a particularly strong > argument. I wrote or reworked most of the constant folding done in gfortran. I think I may be able to speak with some authority as to what the constant folding is doing. Showing the compiler's internal state in comment #3 was only motivated by your comment #2, which appears to show that you don't understand my comment #1. > Surely it's reasonable for the programmer to assume that if y is +Inf, than > log(y) will be also. But, y is not +Inf. > (Though I can see this degenerating into a discussion about -ffloat-store.) This absolutely nothing to do with -ffloat-store. It has to do with misleading documentation. I'll submit a patch to fix that snafu. I suspect that the only legal, but non-portable, method that allows one to get an inf value in a variable is via TRANSFER(). -- http://gcc.gnu.org/bugzilla/show_bug.cgi?id=34230