https://gcc.gnu.org/bugzilla/show_bug.cgi?id=70959
Bug ID: 70959
Summary: Invalid change of value conversion warning message
Product: gcc
Version: unknown
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: fortran
Assignee: unassigned at gcc dot gnu.org
Reporter: w.clodius at icloud dot com
Target Milestone: ---
Created attachment 38415
--> https://gcc.gnu.org/bugzilla/attachment.cgi?id=38415&action=edit
A simplified program generating the inappropriate error
The file
module test_int
use, intrinsic:: iso_fortran_env
integer(int64), parameter :: &
e18 = 1000000000000000000_int64, &
e19 = ( -huge(1_int64) + &
(e18-223372036854775807_int64) &
) - 2
end module test_int
when compiled using
fortran -std=f2008 -fmax-errors=10 -Wall -Wimplicit-interface -O3 -fbacktrace
-fwhole-file -I mod_dir -c -o test_int.o test_int.f90
on Mac OS X version 10.11.4
with version
gfortran --version
GNU Fortran (GCC) 6.1.0
Copyright (C) 2016 Free Software Foundation, Inc.
This is free software; see the source for copying conditions. There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
produces the message
test_int.f90:5:11:
e18 = 1000000000000000000_int64, &
1
Warning: Change of value in conversion from ‘INTEGER(8)’ to ‘REAL(4)’ at (1)
[-Wconversion]
This suggests that the front end is assigning the wrong type to at least one of
e18
e19
or the expression
( -huge(1_int64) + (e18-223372036854775807_int64) ) - 2
According to Dominique D'Humières the following simplified code has the result
! integer(8), parameter :: e18 = 10000000000_8
integer(8), parameter :: e18 = 100000000000_8
integer(8), parameter :: e19 = (e18)
! integer(8), parameter :: e19 = e18
print *, e18, e19
end
warn_conv_db_3.f90:2:32:
integer(8), parameter :: e18 = 100000000000_8
1
Warning: Change of value in conversion from 'INTEGER(8)' to 'REAL(4)' at (1)
[-Wconversion]
The warning is gone if I remove the parentheses in e19 = (e18) or if I replace
100000000000_8 with 10000000000_8.
which suggests that e18 is being assigned the inappropriate type due to the
appearance of (e18) in the definition of e19
