https://gcc.gnu.org/bugzilla/show_bug.cgi?id=113165
Bug ID: 113165
Summary: Code containing more than one type declaration for a
variable results in confusing error messages from
compiler
Product: gcc
Version: 11.4.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: fortran
Assignee: unassigned at gcc dot gnu.org
Reporter: xecej4 at outlook dot com
Target Milestone: ---
Created attachment 56960
--> https://gcc.gnu.org/bugzilla/attachment.cgi?id=56960&action=edit
Fixed form Fortran77 source file that causes compiler to issue confusing
messages
Some old Fortran codes (e.g., www.netlib.org/ode/epsode.f ) may contain
duplicate declarations of some variables. Lines 1239-1241 of epsode.f:
double precision eps, epsj, h, hmax, hmin, pw, save1, save2,
1 ss, t, uround, ymax
double precision d, r, r0, t, yj
The variable t is declared twice, albeit with the same type and kind.
Gfortran correctly flags this error, but seems to go farther and mark the
variable t as implicitly typed single precision REAL, causing the issuing a
number of misleading error messages when the concerned variable is used in
expressions later on in the program unit.
I enclose a short program to illustrate. Please compile the program with (a) no
options, (b) with -Wall and (c) with -fimplicit-none. Case (c) results in:
muldecl.f:4:24:
4 | double precision d,q,r ! 'd' was already declared as double
prec.
| 1
Error: Symbol 'd' at (1) already has basic type of REAL
muldecl.f:7:7:
7 | r = sqrt(d)
| 1
Error: Symbol 'r' at (1) has no IMPLICIT type
I suspect that the multiple declaration of d has caused even the unrepeated
declaration of r to be tainted.
