The following program (pasted in the #fortran IRC channel) is accepted by
gfortran -- unless -std=f2008 is used.
Expected: By default a warning (or error) is printed - if two different values
are used. Maybe one should reject the program altogether - or allow it only
with -std=legacy. -- The program can too easily produce indented results (cf.
below).
However, I think one can still allow double initialization of the same value
with -std=gnu and without a warning.
Without a warning (or better error) one can easily miss unintended double
initializations - e.g. in legacy programs. Additionally, the result of such an
initialization by different values is completely arbitrary as the program below
shows. As variant, one can swap the whole-array initialization ("prefill") with
the "individual values".
ifort always prints "-1" independent of the order, Pathscale seemingly does
what the user intended - the initially set "-1" is later overridden. While
gfortran keeps the initial value, i.e. prints "-1" for the program below but
the "intended" result if one swaps the order.
PROGRAM Foo
C COMMON Variables
PARAMETER (MatDim=4)
PARAMETER (MatMax=MatDim**2)
DOUBLE PRECISION Matrix(MatDim,MatDim)
COMMON /CNMatrix/ Matrix
PRINT *,'Matrix:'
PRINT '(4(4(F5.2,3H ),/))',Matrix
END
BLOCK DATA MatrixData
C COMMON Variables
PARAMETER (MatDim=4)
PARAMETER (MatMax=MatDim**2)
DOUBLE PRECISION Matrix(MatDim,MatDim)
COMMON /CNMatrix/ Matrix
DATA Matrix/MatMax*-1.0/ ! prefill
DATA Matrix(2,1)/2.0/ ! individual values
DATA Matrix(1,2)/3.0/ ! individual values
END
--
Summary: Double initialization: Warn if the value is different
Product: gcc
Version: 4.6.0
Status: UNCONFIRMED
Keywords: diagnostic
Severity: normal
Priority: P3
Component: fortran
AssignedTo: unassigned at gcc dot gnu dot org
ReportedBy: burnus at gcc dot gnu dot org
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=45288
