program capbug(output); (* capbug: capitalization bug in gpc compiler Dr. Thomas D. Schneider National Cancer Institute Laboratory of Experimental and Computational Biology Molecular Information Theory Group Frederick, Maryland 21702-1201 toms@ncifcrf.gov permanent email: toms@alum.mit.edu (use only if first address fails) http://www.lecb.ncifcrf.gov/~toms/ *) const (* begin module version *) version = 1.00; (* of capbug.p 2004 Sep 10 2004 Sep 10, 1.00: origin *) (* end module version *) (* begin module describe.capbug *) (* name capbug: capitalization bug in gpc compiler synopsis capbug(output: out) files output: messages to the user description Demonstrate capitals bug in GPC. The name of a local procedure is objected to by GPC if there is a global by the same name but different capitalization. In theory the compiler should keep track of what is local and what is global anyway, so it should be able to avoid this. It is a problem because if one imports procedures from another program, they are not being treated as pure 'black boxes'. Instead, local variable names are being compared to the global variable names. In otherwords, the scope rule of Pascal is being violated when these warnings are generated. This problem is not fixed by adding the flag: -Widentifier-case-local Warn about an identifier written with varying case within one program/module/unit. examples gpc 20040516, based on gcc-3.3.3 for this program itself gives: capbug.p:113: warning: capitalisation of `x' doesn't match capbug.p:111: warning: previous capitalisation `X' capbug.p:113: warning: capitalisation of `y' doesn't match capbug.p:111: warning: previous capitalisation `Y' capbug.p: In procedure `themain': capbug.p:138: warning: capitalisation of `X' doesn't match capbug.p:113: warning: previous capitalisation `x' capbug.p:139: warning: capitalisation of `Y' doesn't match capbug.p:113: warning: previous capitalisation `y' The result is: capbug 1.00 outside: x = 1 outside: y = 2 inside: x = 3 inside: y = 4 themain: X = 5 themain: Y = 6 which demonstrates that the scope rules are being followed when the progrm runs, because X and Y are set before the calls to routines outside and inside, but they are not affected by those calls. That is, the outside and inside routines have local variables. documentation see also {Manual on GPC that gives the -Widentifier-case-local flag:} http://www.gnu-pascal.de/gpc/GPC-Command-Line-Options.html {Discussion on the topic, "Upper/lower case in identifiers":} http://www.gnu-pascal.de/crystal/gpc/en/raw-mail7665.html author Thomas Dana Schneider bugs technical notes *) (* end module describe.capbug *) var X, Y: integer; (* global X and Y *) procedure outside(x, y: integer); (* an outside procedure *) begin x := 1; y := 2; writeln(output,'outside: x = ',x:1); writeln(output,'outside: y = ',y:1); end; (* begin module capbug.themain *) procedure themain; (* the main procedure of the program *) procedure inside(x, y: integer); (* an inside procedure *) begin x := 3; y := 4; writeln(output,'inside: x = ',x:1); writeln(output,'inside: y = ',y:1); end; begin writeln(output,'capbug ',version:4:2); X := 5; Y := 6; outside(X, Y); inside(X, Y); writeln(output,'themain: X = ',X:1); writeln(output,'themain: Y = ',Y:1); end; (* end module capbug.themain *) begin themain; end.