https://gcc.gnu.org/bugzilla/show_bug.cgi?id=99740
Bug ID: 99740
Summary: floating point exception in rand() in gfortran
Product: gcc
Version: unknown
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: libfortran
Assignee: unassigned at gcc dot gnu.org
Reporter: pvoytas at gmail dot com
Target Milestone: ---
Possible bug in gfortran rand() function?
Included code fails with IEEE divide by zero signalling.
When I request a backtrace, it is from a line with "-log(rand(0))".
Last output to the file for code included below is 0.183492497 on line 7372837.
If I just write the rand(0) to file (not taking the log), the code finishes
with no errors and the values near line 7372837 don't seem to have any weird
values that would account for the error.
Code runs with out errors either way if I use "call random_number(x)" to
generate random numbers. Since I'm porting old code, the backward compatibility
of rand(0) is needed.
(note: Code compiles and runs successfully with either g77 or gfortran on
Centos 6.x machine with distro default gcc)
gcc -v output:
Using built-in specs.
COLLECT_GCC=gcc
COLLECT_LTO_WRAPPER=/opt/ohpc/pub/compiler/gcc/8.3.0/libexec/gcc/x86_64-pc-linux-gnu/8.3.0/lto-wrapper
Target: x86_64-pc-linux-gnu
Configured with: ../configure --disable-multilib
--enable-languages=c,c++,fortran --prefix=/opt/ohpc/pub/compiler/gcc/8.3.0
--disable-static --enable-shared
Thread model: posix
gcc version 8.3.0 (GCC)
Distro:
Oracle Linux (7.9): uname -a gives:
Linux <hostname> 5.4.17-2011.6.2.el7uek.x86_64 #2 SMP Thu Sep 3 14:09:14 PDT
2020 x86_64 x86_64 x86_64 GNU/Linux
compile command:
gfortran -ffpe-trap=zero -g rantest.f
compiles with no errors
runtime errors:
Program received signal SIGFPE: Floating-point exception - erroneous arithmetic
operation.
Backtrace for this error:
#0 0x7fc09a5113ff in ???
#1 0x7fc09ad330bc in ???
#2 0x4008cf in rantest
at /home/pvoytas/ps_cp/accidentals/time_series/rantest.f:10
#3 0x400968 in main
at /home/pvoytas/ps_cp/accidentals/time_series/rantest.f:13
Floating exception (core dumped)
code:
program rantest
implicit none
integer*4 i
real*8 x
do i=1,10000000
c call random_number(x)
c write(11,*)x
c write(11,*)rand(0)
write(11,*)-log(rand(0))
enddo
stop
end
