[sdcc-devel] [ sdcc-Bugs-553398 ] PIC backend: string literals

[<no...@so...>]

Bugs item #553398, was opened at 2002-05-07 14:05
You can respond by visiting: 
http://sourceforge.net/tracker/?func=detail&atid=100599&aid=553398&group_id=599

Category: None
Group: None
Status: Open
Resolution: None
Priority: 5
Submitted By: Linas Vepstas (linas)
Assigned to: Nobody/Anonymous (nobody)
Summary: PIC backend: string literals

Initial Comment:
I suspect you know this already, but:
string literals seem "dangerous": 


main()
{
        char * p = "hellow world!\r\n";

        // copy string to serial port (serial port setup omitted)
        while (1)
        {
                if (0 == *p) break;
                TXREG = *p;
                p++;
        }
}


generates FSR/INDF addressing whereas a CALL would have been the correct 
thing to do.   I just noticed that declaring it "const char *" does
seem to use CALL (I assume correctly, I haven't checked).   However, 
its easy not to know/guess that "const char * " is the right thing to do 
...  maybe the compiler should generate a warning:
"WARNING: char * cannot be used to address string literals! Maybe you
want to use const char *" or something like that ...
 
--linas

Below is the broken code...



               00173 ;;      -----------------------------------------
               00174 ;;       function main
               00175 ;;      -----------------------------------------
               00176 ;_main:
0000           00177 _main   ;Function start
0000 300E      00192         MOVLW   LOW(__str_0)    ;key=000,flow 
seq=001
0001 00A0      00203         MOVWF   r0x20   ;key=001,flow seq=001
0002 00A1      00204         MOVWF   r0x21   ;key=002,flow seq=001
0003           00216 _00108_DS_
0003 0821      00217         MOVF    r0x21,W ;key=000,flow seq=002
0004 0084      00218         MOVWF   FSR     ;key=001,flow seq=002
0005 0800      00219         MOVF    INDF,W  ;key=002,flow seq=002
0006 00A2      00229         MOVWF   r0x22   ;key=003,flow seq=002
0007 1903      00230         BTFSC   STATUS,2        ;key=004,flow 
seq=002
0008 280D      00233         GOTO    _00110_DS_      ;key=000,flow 
seq=003
0009 0822      00247         MOVF    r0x22,W ;key=000,flow seq=004
000A 0099      00248         MOVWF   _TXREG  ;key=001,flow seq=004
000B 0AA1      00259         INCF    r0x21,F ;key=002,flow seq=004
000C 2803      00263         GOTO    _00108_DS_      ;key=003,flow
seq=004
000D           00276 _00110_DS_
000D 0008      00277         RETURN          ;key=000,flow seq=005
               00284 ;; Starting pCode block
               00285 ;; __str_0 = hellow world!^M
               00286
000E           00287 __str_0
000E 3468      00288         RETLW   0x68    ;key=000,flow seq=007
000F 3465      00290         RETLW   0x65    ;key=000,flow seq=008
0010 346C      00292         RETLW   0x6c    ;key=000,flow seq=009
0011 346C      00294         RETLW   0x6c    ;key=000,flow seq=00a
0012 346F      00296         RETLW   0x6f    ;key=000,flow seq=00b
0013 3477      00298         RETLW   0x77    ;key=000,flow seq=00c
0014 3420      00300         RETLW   0x20    ;key=000,flow seq=00d
0015 3477      00302         RETLW   0x77    ;key=000,flow seq=00e
0016 346F      00304         RETLW   0x6f    ;key=000,flow seq=00f
0017 3472      00306         RETLW   0x72    ;key=000,flow seq=010
0018 346C      00308         RETLW   0x6c    ;key=000,flow seq=011
0019 3464      00310         RETLW   0x64    ;key=000,flow seq=012
001A 3421      00312         RETLW   0x21    ;key=000,flow seq=013
001B 340D      00314         RETLW   0x0d    ;key=000,flow seq=014
001C 340A      00316         RETLW   0x0a    ;key=000,flow seq=015
001D 3400      00318         RETLW   0x00    ;key=000,flow seq=016




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