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Annotation of researchv10no/cmd/f77/README, revision 1.1

1.1     ! root        1: Feb. 1988: dmg modified f77pass1 to put out stab info to make .o's
        !             2: compiled by f77 -g look like corresponding .o's from cc -g , with the
        !             3: conventions described by Feldman and Weinberger in the Fortran 77
        !             4: section of Volume 2B of the Seventh Edition UNIX PROGRAMMER'S
        !             5: MANUAL.  This makes pi useful with f77 -g.
        !             6: 
        !             7: COMPLEX variables appear to be
        !             8:        struct complex { float real, imag; };
        !             9: DOUBLE COMPLEX variables similarly appear to be
        !            10:        struct dcomplex { double real, imag; };
        !            11: 
        !            12: Norman's COMMON stab entries are retained (in hopes that some day
        !            13: pi -- or some other debugger -- might be made to exploit them);
        !            14: see alt/README.  In addition, COMMON blocks are made to appear as
        !            15: global structs:
        !            16:        COMMON /ABC/ N, X
        !            17: looks like
        !            18:        extern struct abc_COMMON_ {int n; float x;} abc_;
        !            19: 
        !            20: If the same COMMON block occurs in 
        !            21: 
        !            22: CHARACTER variables are uniformly made to appear as char* or char[] ,
        !            23: so one can easily see more than the first character with pi.
        !            24: 
        !            25: Omission: stab entries for the implicit length parameters associated
        !            26: with CHARACTER arguments are currently omitted.  (But CHARACTER functions
        !            27: have stabs entries for their return value and return value lengths.)
        !            28: 
        !            29: Regarding what follows, also read Norman's comments in alt/README.
        !            30: 
        !            31: Thanks to changes in pi by Tom Cargill, COMMON variables appear
        !            32: to be local variables in each subprogram in which they are used.
        !            33: COMMON blocks also appear in pi's Globals menu.  If several
        !            34: subprograms use different names for the components of a COMMON
        !            35: block, then f77 merges these into the global struct that describes
        !            36: the COMMON block, honoring only the first occurrence of each name.
        !            37: 
        !            38: EQUIVALENCEs involving COMMON blocks are handled as above: the
        !            39: global struct for the COMMON block gets more components, and all
        !            40: components appear as local variables.  EQUIVALENCEd local variables
        !            41: also simply appeared in pi's local variable menu.  This required
        !            42: more tinkering by tac and emission by f77 of a stab sequence of
        !            43: the form
        !            44: 
        !            45:        .stabn  0xe2,0,0                #0xe2 = BCOMM
        !            46:        .stabn  symtype,0,address       #symtype = STSYM (0x26) or LCSYM (0x28)
        !            47:        .stabs  "vname1",0,type,offset
        !            48:        # type modifiers (SSYM, DIM), if required
        !            49:        .stabs  "vname2",0,type,offset
        !            50:        # type modifiers (SSYM, DIM), if required
        !            51:        ....
        !            52:        .stabn  0xe8,0,0,0              #0xe8 = ECOML
        !            53: 
        !            54: This departs from Norman's scheme by moving the address from the
        !            55: ECOML line (where we can't get it right without tinkering /bin/as
        !            56: and /bin/ld) to a separate STSYM or LCSYM line right after the BCOMM
        !            57: (in which we get the right address).  This differs from COMMON in
        !            58: that the name field of the BCOMM is null.  (It would be nicer if
        !            59: COMMON and EQUIVALENCE could be handled uniformly, but the addressing
        !            60: restrictions of /bin/as and /bin/ld prevent this.)
        !            61: 
        !            62: 
        !            63: Bug fixes made 30 June 1989 to /n/bowell/usr/src/cmd/f77:
        !            64: 1. Type of PARAMETERs honored.
        !            65: 2. Comma allowed in DO: do 10, i = 1, n
        !            66: 3. Stmt function actual arg can be subscripted var of same name as the dummy.
        !            67: 4. Calling sequence expected by functions and subroutines adjusted to
        !            68:    match the calling sequence passed to same.  Previously, procedures
        !            69:    expected a length parameter to accompany procedure arguments.  This
        !            70:    change eliminates the old "bad code may have been generated" warning.
        !            71: 5. DATA statements with general implied DOs now work.  Previously only
        !            72:    an initial, singly nested DO worked.
        !            73: 6. A loop like "DO 10 i = 1, 1, -1" no longer has its range omitted.
        !            74: 7. ASSIGNed FORMAT labels work.
        !            75: 8. New flags -b and -B added: -b warns when the above bug fixes affect
        !            76:    generated objects; -B reverts to the previous buggy behavior.
        !            77: 9. Default max number of statement labels increased (from 201 to 801).
        !            78: 10. Disallow statement functions among executables, even when there
        !            79:     are DATA statements.

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