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Problem w. built-in function toupper (convert to uppercase)

 
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Quinni



Joined: 24 Mar 2006
Posts: 1

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Problem w. built-in function toupper (convert to uppercase)
PostPosted: Fri Mar 24, 2006 11:21 am     Reply with quote
Hi,
Does anyone know why the line
strnew[i]=toupper(*ptr);
does not work? It works in every ANSI C-Compiler but not with the CCS-Compiler. Its a simple task converting a char to uppercase.
I have found the work around you can see below, but i would like to know why the specific line does not work.
This is only a code fragment - all pointers and variables are set correctly!
Thx for any answer.
Quinni

char c;
char * ptr;


This does NOT Work

strnew[i]=toupper(*ptr); // this line does not work as i expect
//convert to uppercase and store it in a new string

This Code works:
c=*ptr; //first store dereferenced pointer to c
strnew[i]=toupper(c); //convert c to uppercase and store it in new string
treitmey



Joined: 23 Jan 2004
Posts: 1094
Location: Appleton,WI USA

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PostPosted: Fri Mar 24, 2006 12:39 pm     Reply with quote
..

Last edited by treitmey on Fri Mar 24, 2006 4:05 pm; edited 1 time in total
PCM programmer



Joined: 06 Sep 2003
Posts: 21708

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PostPosted: Fri Mar 24, 2006 2:51 pm     Reply with quote
It looks like the problem occurs when the result from toupper()
is assigned to an array with a variable index. Look at the test
program shown below. It produces the results shown below. It's only
incorrect in the 2nd test. I tested this with PCM vs. 3.248 and 3.449.
Code:

first result = 41

2nd result = 61    <-- incorrect

3rd result = 41

(Values are in Hex)


Code:

#include <16F877.H>
#fuses XT, NOWDT, NOPROTECT, BROWNOUT, PUT, NOLVP
#use delay(clock=4000000)
#use rs232(baud=9600, xmit=PIN_C6, rcv=PIN_C7, ERRORS)

//============================
void main()
{
char *ptr;
char c;
char string[10] = {"a"};
char strnew[10];
int8 i;

ptr = string;
c = toupper(*ptr);
printf("first result = %x \n\r", c);

i = 0;
ptr = string;
strnew[i] = toupper(*ptr);
printf("2nd result = %x \n\r", strnew[0]);

ptr = string;
strnew[0] = toupper(*ptr);
printf("3rd result = %x \n\r", strnew[0]);

while(1);
}

=======================

I don't have time to investigate this right now. I've got to
do some work at the company. But as a work-around you can
use the following replacement function for toupper(). I tested
it with the program above and it always works.
Code:

char my_toupper(char c)
{
if(c >= 'a' && c <= 'z')
   c -= 0x20;
return(c);
}
Ttelmah
Guest
PostPosted: Sat Mar 25, 2006 9:02 am     Reply with quote
Yes, it a definite bug.
If you look at the assembler generated, in the specific case of using a pointer reference on both sides of the equation (remember in C an array, and pointer are just two different constructs giving the same result), with a variable index on the left side, the code generates:
Code:

.................... strnew[i] = (toupper(*ptr));
00BE:  MOVLW  2D
00BF:  ADDWF  37,W
00C0:  MOVWF  38
00C1:  MOVF   21,W
00C2:  MOVWF  04
00C3:  MOVF   00,W
00C4:  MOVWF  39
00C5:  SUBLW  60
00C6:  BTFSC  03.0
00C7:  GOTO   0CF
00C8:  MOVF   39,W
00C9:  SUBLW  7A
00CA:  BTFSS  03.0
00CB:  GOTO   0CF
00CC:  MOVF   39,W
00CD:  ANDLW  DF   //Correctly generates result
00CE:  GOTO   0CF
00CF:  MOVF   38,W  //Uurgh, W is now destroyed
00D0:  MOVWF  04
00D1:  MOVF   39,W //Retreive the original value...
00D2:  MOVWF  00   //and save this.

I'd report this, but in the meantime, probably use:
Code:

#define toupper(x) ((x)>='a' && (x)<='z')?(x&0xDF):(x)

Which has the advantage of 'overwriting' the existing declaration, without having to change the rest of the code (though produces slightly bulkier code).

Best Wishes
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