Here is a summary of all the options specific to GNU Fortran, grouped by type. Explanations are in the following sections.
          -fall-intrinsics  -ffree-form  -fno-fixed-form 
          -fdollar-ok  -fimplicit-none  -fmax-identifier-length 
          -std=std -fd-lines-as-code  -fd-lines-as-comments 
          -ffixed-line-length-n  -ffixed-line-length-none 
          -ffree-line-length-n  -ffree-line-length-none 
          -fdefault-double-8  -fdefault-integer-8  -fdefault-real-8 
          -fcray-pointer  -fopenmp  -fno-range-check -fbackslash -fmodule-private
               -cpp -dD -dI -dM -dN -dU -fworking-directory 
          -imultilib dir -iprefix file -isysroot dir 
          -iquote -isystem dir -nocpp -nostdinc -undef 
          -Aquestion=answer -A-question[=answer] 
          -C -CC -Dmacro[=defn] -Umacro -H -P
               -fmax-errors=n 
          -fsyntax-only  -pedantic  -pedantic-errors 
          -Wall  -Waliasing  -Wampersand  -Warray-bounds -Wcharacter-truncation 
          -Wconversion -Wimplicit-interface  -Wimplicit-procedure  -Wline-truncation 
          -Wintrinsics-std  -Wsurprising  -Wno-tabs  -Wunderflow  -Wunused-parameter 
          -Wintrinsic-shadow  -Wno-align-commons
               -fdump-fortran-original  -fdump-fortran-optimized 
          -ffpe-trap=list  -fdump-core -fbacktrace -fdump-parse-tree
     -Idir -Jdir -fintrinsic-modules-path dir
-static-libgfortran
          -fconvert=conversion  -fno-range-check
          -frecord-marker=length   -fmax-subrecord-length=length
          -fsign-zero
               -fno-automatic  -ff2c  -fno-underscoring 
          -fno-whole-file -fsecond-underscore 
          -fbounds-check -fcheck-array-temporaries  -fmax-array-constructor =n 
          -fcheck=<all|array-temps|bounds|do|mem|pointer|recursion> 
          -fcoarray=<none|single> -fmax-stack-var-size=n 
          -fpack-derived  -frepack-arrays  -fshort-enums  -fexternal-blas 
          -fblas-matmul-limit=n -frecursive -finit-local-zero 
          -finit-integer=n -finit-real=<zero|inf|-inf|nan|snan> 
          -finit-logical=<true|false> -finit-character=n 
          -fno-align-commons -fno-protect-parens -frealloc-lhs