This option causes all intrinsic procedures (including the GNU-specificextensions) to be accepted. This can be useful with -std= toforce standard-compliance but get access to the full range of intrinsicsavailable with gfortran. As a consequence, -Wintrinsics-stdwill be ignored and no user-defined procedure with the same name as anyintrinsic will be called except when it is explicitly declared EXTERNAL.
Promote all REAL(KIND=M) entities to REAL(KIND=N) entities.If REAL(KIND=N) is unavailable, then an error will be issued.The -freal-4- flags also affect the default real kind and the-freal-8- flags also the double-precision real kind. All otherreal-kind types are unaffected by this option. The promotion is alsoapplied to real literal constants of default and double-precision kindand a specified kind number of 4 or 8, respectively.However, -fdefault-real-8, -fdefault-real-10,-fdefault-real-10, and -fdefault-double-8 take precedencefor the default and double-precision real kinds, both for real literalconstants and for declarations without a kind number.Note that for REAL(KIND=KIND(1.0)) the literal may get promoted andthen the result may get promoted again.These options should be used with care and may not be suitable for yourcodes. Areas of possible concern include calls to external procedures,alignment in EQUIVALENCE and/or COMMON, generic interfaces,BOZ literal constant conversion, and I/O and calls to intrinsic procedureswhen passing a value to the kind= dummy argument. Inspection of theintermediate representation of the translated Fortran code, produced by-fdump-fortran-original or -fdump-tree-original, is suggested.
Introduction to Programming with Fortran - With Coverage of Fortran 90, 95, 2003, 2008 and 77 (2nd e
Efforts are underway to develop a revision to Fortran 2003,tentatively called Fortran 2008. As with Fortran 95, this is intendedto be a minor upgrade, incorporating clarifications and corrections toFortran 2003, as well as introducing a select few new capabilities. Asof February 2007, the proposed new capabilities include[12]
Over the decades, Fortran has undergone several major versions to keep up with current programming trends, with the most popular versions of Fortran being Fortran 77, 90, 95, 2003, 2008, and more recently, 2018. The language continues to evolve and be refined to meet the changing needs of the latest ground-breaking scientific and engineering research.
The GNU gfortran comiler flags "-fno-underscoring" (older f77: "-fno-underscore") and "-fno-second-underscore"will alter the default naming in the object code and thus affect linking.One may view the object file with the command nm (i.e.: nm file.o).
Note: The case in FORTRAN is NOT preserved and is represented in lower case in the object file. The gfortran compiler option "-fcase-lower is default.The older g77 compiler option "-fsource-case-lower" is also default.GNU g77 FORTRAN can be case sensitive with the compile option "-fsource-case-preserve".
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