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Problem with PCD compiler and const declaration

 
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Regas



Joined: 08 Jan 2010
Posts: 8

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Problem with PCD compiler and const declaration
PostPosted: Fri Jan 08, 2010 5:21 am     Reply with quote

The following code fragment works well:
Code:

         char Strg[] ={"Test"};
         int8 ii;

         ii =0;
         while (Strg[ii] !=0){
         ++ii;
         }

But when I use a const variable:
Code:

         const char Strg[] ={"Test"};
         int8 ii;

         ii =0;
         while (Strg[ii] !=0){
         ++ii;
         }

The program execution failed by entering the while loop.
The list File contains a call statement to an empty ROM location.
Code:

004AA EF6862         CLR.B   862            : [862] = 0
                         ..............................          while (Strg[ii] !=0){
004AC BFC862         MOV.B   862,W0L        : W0L = [862]
004AE FB0000         SE      W0,W0          : W0 = sign-extended W0
004B0 020100 000000  CALL    100            :
004B4 E00400         CP0.B   W0L            : Status set for W0L - 0
004B6 320003         BRA     Z,4BE          : if W0L=0 GoTo 4BE
                         ..............................          ++ii;
004B8 EC6862         INC.B   0862           : [4BE] = [4BE] + 1
                         ..............................          }
004BA 0404AC 000000  GOTO    4AC            :

How can I use const variables with PCD compiler?

PS: The const declaration works well by using PCH compiler.
FvM



Joined: 27 Aug 2008
Posts: 2337
Location: Germany

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PostPosted: Fri Jan 08, 2010 9:36 am     Reply with quote

Your const string example is working for me with PCD V4.104.
Quote:
The list File contains an call statement to an empty ROM location
Did you check the ROM content?
The code is not listed, unless you remove the #nolist pragma from the header file.
Regas



Joined: 08 Jan 2010
Posts: 8

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PostPosted: Fri Jan 08, 2010 3:42 pm     Reply with quote

Hi FvM

Thank you for help.

Yes I use PCD V4.104.

The last posted routine is really working when compiled separately sorry.

I could not find the
Code:
 #nolist pragma 

in the header file, but the constant tables are not listed in the list file.

In the following code the string "ADC Kanal2_A" gives no output. But when I remove the declaration const both strings will work.
Code:

char ADC1[] ={ "ADC Kanal1_V"};
const char ADC2[] ={ "ADC Kanal2_A"};
.
.
.

switch (LCDSw){
         case 1 : if (LCD_Ausgabe (41, &ADC1)) LCDSw =2;
                  break;
         case 2 : if (LCD_Ausgabe (61, &ADC2)) LCDSw =3;
                  break;
.
.
.

Are pointers not allowed with const strings ?
FvM



Joined: 27 Aug 2008
Posts: 2337
Location: Germany

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PostPosted: Fri Jan 08, 2010 4:03 pm     Reply with quote

Yes, pointers make the difference. The problem is, that a const string pointer can be only dereferenced by a
TBLRD instruction sequence, so it has to be treated different by the compiler. According to reported CCS C
features, constant string pointers should work now, but I never saw it with PCD. It surely didn't work e.g. half
a year ago, and I didn't try with newer versions. But you should check yourself. Surely, it must use a different
pointer type in LCD_Ausgabe().

To tell my personal opinion: The mixture of unclear documentation and announced but actually unsupported
features doesn't really motivate me to check for updated compiler functionality.

Best regards,
Frank
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