https://gcc.gnu.org/bugzilla/show_bug.cgi?id=99761
Bug ID: 99761
Summary: Warn flag for non-kind specified mixing
Product: gcc
Version: fortran-dev
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: fortran
Assignee: unassigned at gcc dot gnu.org
Reporter: nickpapior at gmail dot com
Target Milestone: ---
Some context here:
https://github.com/j3-fortran/fortran_proposals/issues/201
The basic message is that users may forget to add kind specifications for
constants which are assigned to higher precision values which then loses the
extra bits.
Simplest example:
real(8), parameter :: pi = 3.14159265358979323846
which actually only stores the floating point value and store that in a double
precision variable, thereby loosing precision.
My proposal would be to add a flag which warns about misused kinds:
program test
real(8), parameter :: const = 1.4435435345345
real(8), parameter :: const2 = 1./3.
real(8), parameter :: const3 = 1._4/4._4
print *, 1./3. * const
end program test
it would be nice if the above could be compiled with gfortran -Wpedantic-kind
and something like this would be issued:
2 | real(8), parameter :: const = 1.4435435345345
1
Warning: Constant expression at (1) is in lower precision than variable.
3 | real(8), parameter :: const2 = 1./3.
1
Warning: Constant expression at (1) is in lower precision than variable.
3 | real(8), parameter :: const2 = 1./3.
1
Warning: Constant expression at (1) is in lower precision than variable.
5 | print *, 1./3. * const
1 2
Warning: Constant at (1) has lower precision than variable at (2)
Line 4 is silently ignored due to explicit kind specification.
I think such an enhancement would be extremely useful to hunt down mis-typed
kind specifiers.
