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(g77-295.info)Case Sensitivity
Case Sensitivity
================
GNU Fortran offers the programmer way too much flexibility in
deciding how source files are to be treated vis-a-vis uppercase and
lowercase characters. There are 66 useful settings that affect case
sensitivity, plus 10 settings that are nearly useless, with the
remaining 116 settings being either redundant or useless.
None of these settings have any effect on the contents of comments
(the text after a `c' or `C' in Column 1, for example) or of character
or Hollerith constants. Note that things like the `E' in the statement
`CALL FOO(3.2E10)' and the `TO' in `ASSIGN 10 TO LAB' are considered
built-in keywords, and so are affected by these settings.
Low-level switches are identified in this section as follows:
A Source Case Conversion:
0 Preserve (see Note 1)
1 Convert to Upper Case
2 Convert to Lower Case
B Built-in Keyword Matching:
0 Match Any Case (per-character basis)
1 Match Upper Case Only
2 Match Lower Case Only
3 Match InitialCaps Only (see tables for spellings)
C Built-in Intrinsic Matching:
0 Match Any Case (per-character basis)
1 Match Upper Case Only
2 Match Lower Case Only
3 Match InitialCaps Only (see tables for spellings)
D User-defined Symbol Possibilities (warnings only):
0 Allow Any Case (per-character basis)
1 Allow Upper Case Only
2 Allow Lower Case Only
3 Allow InitialCaps Only (see Note 2)
Note 1: `g77' eventually will support `NAMELIST' in a manner that is
consistent with these source switches--in the sense that input will be
expected to meet the same requirements as source code in terms of
matching symbol names and keywords (for the exponent letters).
Currently, however, `NAMELIST' is supported by `libg2c', which
uppercases `NAMELIST' input and symbol names for matching. This means
not only that `NAMELIST' output currently shows symbol (and keyword)
names in uppercase even if lower-case source conversion (option A2) is
selected, but that `NAMELIST' cannot be adequately supported when
source case preservation (option A0) is selected.
If A0 is selected, a warning message will be output for each
`NAMELIST' statement to this effect. The behavior of the program is
undefined at run time if two or more symbol names appear in a given
`NAMELIST' such that the names are identical when converted to upper
case (e.g. `NAMELIST /X/ VAR, Var, var'). For complete and total
elegance, perhaps there should be a warning when option A2 is selected,
since the output of NAMELIST is currently in uppercase but will someday
be lowercase (when a `libg77' is written), but that seems to be
overkill for a product in beta test.
Note 2: Rules for InitialCaps names are:
- Must be a single uppercase letter, *or*
- Must start with an uppercase letter and contain at least one
lowercase letter.
So `A', `Ab', `ABc', `AbC', and `Abc' are valid InitialCaps names,
but `AB', `A2', and `ABC' are not. Note that most, but not all,
built-in names meet these requirements--the exceptions are some of the
two-letter format specifiers, such as `BN' and `BZ'.
Here are the names of the corresponding command-line options:
A0: -fsource-case-preserve
A1: -fsource-case-upper
A2: -fsource-case-lower
B0: -fmatch-case-any
B1: -fmatch-case-upper
B2: -fmatch-case-lower
B3: -fmatch-case-initcap
C0: -fintrin-case-any
C1: -fintrin-case-upper
C2: -fintrin-case-lower
C3: -fintrin-case-initcap
D0: -fsymbol-case-any
D1: -fsymbol-case-upper
D2: -fsymbol-case-lower
D3: -fsymbol-case-initcap
Useful combinations of the above settings, along with abbreviated
option names that set some of these combinations all at once:
1: A0-- B0--- C0--- D0--- -fcase-preserve
2: A0-- B0--- C0--- D-1--
3: A0-- B0--- C0--- D--2-
4: A0-- B0--- C0--- D---3
5: A0-- B0--- C-1-- D0---
6: A0-- B0--- C-1-- D-1--
7: A0-- B0--- C-1-- D--2-
8: A0-- B0--- C-1-- D---3
9: A0-- B0--- C--2- D0---
10: A0-- B0--- C--2- D-1--
11: A0-- B0--- C--2- D--2-
12: A0-- B0--- C--2- D---3
13: A0-- B0--- C---3 D0---
14: A0-- B0--- C---3 D-1--
15: A0-- B0--- C---3 D--2-
16: A0-- B0--- C---3 D---3
17: A0-- B-1-- C0--- D0---
18: A0-- B-1-- C0--- D-1--
19: A0-- B-1-- C0--- D--2-
20: A0-- B-1-- C0--- D---3
21: A0-- B-1-- C-1-- D0---
22: A0-- B-1-- C-1-- D-1-- -fcase-strict-upper
23: A0-- B-1-- C-1-- D--2-
24: A0-- B-1-- C-1-- D---3
25: A0-- B-1-- C--2- D0---
26: A0-- B-1-- C--2- D-1--
27: A0-- B-1-- C--2- D--2-
28: A0-- B-1-- C--2- D---3
29: A0-- B-1-- C---3 D0---
30: A0-- B-1-- C---3 D-1--
31: A0-- B-1-- C---3 D--2-
32: A0-- B-1-- C---3 D---3
33: A0-- B--2- C0--- D0---
34: A0-- B--2- C0--- D-1--
35: A0-- B--2- C0--- D--2-
36: A0-- B--2- C0--- D---3
37: A0-- B--2- C-1-- D0---
38: A0-- B--2- C-1-- D-1--
39: A0-- B--2- C-1-- D--2-
40: A0-- B--2- C-1-- D---3
41: A0-- B--2- C--2- D0---
42: A0-- B--2- C--2- D-1--
43: A0-- B--2- C--2- D--2- -fcase-strict-lower
44: A0-- B--2- C--2- D---3
45: A0-- B--2- C---3 D0---
46: A0-- B--2- C---3 D-1--
47: A0-- B--2- C---3 D--2-
48: A0-- B--2- C---3 D---3
49: A0-- B---3 C0--- D0---
50: A0-- B---3 C0--- D-1--
51: A0-- B---3 C0--- D--2-
52: A0-- B---3 C0--- D---3
53: A0-- B---3 C-1-- D0---
54: A0-- B---3 C-1-- D-1--
55: A0-- B---3 C-1-- D--2-
56: A0-- B---3 C-1-- D---3
57: A0-- B---3 C--2- D0---
58: A0-- B---3 C--2- D-1--
59: A0-- B---3 C--2- D--2-
60: A0-- B---3 C--2- D---3
61: A0-- B---3 C---3 D0---
62: A0-- B---3 C---3 D-1--
63: A0-- B---3 C---3 D--2-
64: A0-- B---3 C---3 D---3 -fcase-initcap
65: A-1- B01-- C01-- D01-- -fcase-upper
66: A--2 B0-2- C0-2- D0-2- -fcase-lower
Number 22 is the "strict" ANSI FORTRAN 77 model wherein all input
(except comments, character constants, and Hollerith strings) must be
entered in uppercase. Use `-fcase-strict-upper' to specify this
combination.
Number 43 is like Number 22 except all input must be lowercase. Use
`-fcase-strict-lower' to specify this combination.
Number 65 is the "classic" ANSI FORTRAN 77 model as implemented on
many non-UNIX machines whereby all the source is translated to
uppercase. Use `-fcase-upper' to specify this combination.
Number 66 is the "canonical" UNIX model whereby all the source is
translated to lowercase. Use `-fcase-lower' to specify this
combination.
There are a few nearly useless combinations:
67: A-1- B01-- C01-- D--2-
68: A-1- B01-- C01-- D---3
69: A-1- B01-- C--23 D01--
70: A-1- B01-- C--23 D--2-
71: A-1- B01-- C--23 D---3
72: A--2 B01-- C0-2- D-1--
73: A--2 B01-- C0-2- D---3
74: A--2 B01-- C-1-3 D0-2-
75: A--2 B01-- C-1-3 D-1--
76: A--2 B01-- C-1-3 D---3
The above allow some programs to be compiled but with restrictions
that make most useful programs impossible: Numbers 67 and 72 warn about
*any* user-defined symbol names (such as `SUBROUTINE FOO'); Numbers 68
and 73 warn about any user-defined symbol names longer than one
character that don't have at least one non-alphabetic character after
the first; Numbers 69 and 74 disallow any references to intrinsics; and
Numbers 70, 71, 75, and 76 are combinations of the restrictions in
67+69, 68+69, 72+74, and 73+74, respectively.
All redundant combinations are shown in the above tables anyplace
where more than one setting is shown for a low-level switch. For
example, `B0-2-' means either setting 0 or 2 is valid for switch B.
The "proper" setting in such a case is the one that copies the setting
of switch A--any other setting might slightly reduce the speed of the
compiler, though possibly to an unmeasurable extent.
All remaining combinations are useless in that they prevent
successful compilation of non-null source files (source files with
something other than comments).
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