The expression/condition in an arithmetic if statement appears to be evaluated
multiple times when it is zero or negative. This is particularly bad when the
expression is a function that depends on input or has state associated with it.
Example:
program lll
integer myfunc
do 99 i=1,10
if (myfunc(0)) 10,20,30
10 write (6,*) 'negative'
goto 99
20 write (6,*) 'zero'
goto 99
30 write (6,*) 'positive'
goto 99
99 continue
end
integer function myfunc(int)
integer value
read (5,*) value
myfunc = value
return
end
Sample input/output:
1
positive
0
3
zero
-1
3
zero
4
positive
0
0
zero
Workaround:
Introduce a temporary expression for the if test condition/expression or
convert obsolete arithmetic if to an if-then-else statement.
--
Summary: Multiple evaluations of arithmetic if condition
Product: gcc
Version: 4.1.1
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: fortran
AssignedTo: unassigned at gcc dot gnu dot org
ReportedBy: mfpasik at sandia dot gov
GCC build triplet: i686-pc-linux-gnu
GCC host triplet: i686-pc-linux-gnu
GCC target triplet: i686-pc-linux-gnu
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=28439
